After reading this article as well as the relevant Wikipedia entry [1], I still don't get what's supposedly "wrong" with the triune brain model.
In fact, this article seems to set it up as a bit of a straw man. The main rebuttals in this article are 1) that evolution is branched rather than linear, 2) that larger brains aren't necessarily more complex, and 3) that evolution modifies existing brain structures in addition to adding new layers.
But all of that seems rather obvious, and doesn't really refute the triune brain theory at all.
Isn't it scientifically true that we have a basal ganglia which evolved from reptiles, a limbic system also present mammals, and a neocortex that works similarly to that in other primates, dolphins, and elephants? And each of those map to certain types of behaviors, that we see in these species?
The triune brain hypothesis doesn't seem "wrong", it just seems like a simple categorization that is useful for making big-picture distinctions.
Am I missing something? I literally don't understand what is even being "refuted" here, because the refutations don't seem to match the claims at all.
> and 3) that evolution modifies existing brain structures in addition to adding new layers.
As I understood it, their point was that evolution does not add new layers, evolution of the brain always happens by modifying the existing structure.
Which is why a "stratified" view of the brain with evolutionary older layers near the center and newer layers near the surface is incorrect.
The implications of this belief then led to incorrect assumptions about both humans and (non-human) animals: That the human brain is an "animal brain plus something else" and therefore automatically superior - and inversely that animal brains are "human brains minus something" and therefore automatically inferior. The article argues against both positions.
Is the neocortex not an outer layer? That is not present in reptiles? So how is the stratified model incorrect as a high-level structural categorization?
The triune model doesn't claim our brain grows additively in rings like trees. It's merely an observation about the primary evolutionary origins of the three parts. Just those three.
And the superior/inferior characterization is not part of the triune model. You are free to interpret it that way if you want, but it's not part of it, so it's not a rebuttal.
> Is the neocortex not an outer layer? That is not present in reptiles? So how is the stratified model incorrect as a high-level structural categorization?
Not sure about reptiles, but the author write this about mammals:
> Neurobiologists do not debate whether any cortical regions are evolutionarily newer in some mammals than others. To be clear, even the prefrontal cortex, a region associated with reason and action planning, is not a uniquely human structure. Although there is debate concerning the relative size of the prefrontal cortex in humans compared with nonhuman animals (Passingham & Smaers, 2014; Sherwood, Bauernfeind, Bianchi, Raghanti, & Hof, 2012; Teffer & Semendeferi, 2012), all mammals have a prefrontal cortex.
I also read some interesting papers a few years ago about corvids - particular New Caledonian Crows: Those animals do not have a neocortex and hence were thought incapable of many higher-level cognitive tasks, such as planning, tool use, etc. Turned out the crows were in fact capable of them. One hypothesis I read suggested that, as crow brains are structured differently, another structure may have taken the role that the neocortex has in humans.
So even if it's an anatomical distinction, it's an unreliable indicator of mental capacity.
OK, but again -- none of that refutes the triune brain hypothesis at all.
Literally nobody is claiming that only humans have neocortexes.
Nor is anyone claiming it's an indicator of mental capacity. The recent discoveries about crows were interesting, but that doesn't have anything to do with the fact that the neocortex in mammals plays a particular, functional, well-recognized role.
> The triune brain consists of the reptilian complex (basal ganglia), the paleomammalian complex (limbic system), and the neomammalian complex (neocortex), viewed each as independently conscious, and as structures sequentially added to the forebrain in the course of evolution. According to the model, the basal ganglia are in charge of our primal instincts, the limbic system is in charge of our emotions and the neocortex is responsible for objective or rational thoughts.
We disproved:
- the sequentially added nature
- what these zones are responsible for
So in the end we're only left with a semi-arbitrary split of the brain in 3 zones and none of the hypothised implications. That to me refutes the hypothesis as a whole, and we're keeping the zone naming by sheer inertia.
No one thinks the older structures are static. No one is arguing that.
It's a simplified model about the origin.
This argument is akin to saying we're not "newer" apes ala
> The refutation is of the idea that it’s a strictly chronological ordering of species, with the old species still inside and intact.
The correct view is that while homosapiens are indeed mostly "newer", the “older” apes were also modified throughout evolution
I mean… the quote from TFA that they are arguing against is
> As Paul MacLean (1964), originator of the triune-brain theory, stated,
>> man, it appears, has inherited essentially three brains. Frugal Nature in developing her paragon threw nothing away. The oldest of his brains is basically reptilian; the second has been inherited from lower mammals; and the third and newest brain is a late mammalian development which reaches a pinnacle in man and gives him his unique power of symbolic language.
And they quote other textbooks that are making claims along these lines too; this is right at the beginning of TFA. So I think you are wrong that “no one thinks that”.
Of course they don’t think the old brains are 100% static but there are claims that they are largely conserved.
It’s an incorrect and misleading model about the origin. Bat wings and bird wings share many traits but the common answer didn’t fly it’s simply convergent evolution. The brain structures of that same common ancestor is only vaguely related to modern structures in mammals and reptiles.
Modern reptiles, birds, and humans have experienced the same amount of evolution. There’s similar traits, but we don’t call whale flippers hands because that’s what the structures was in some of their ancestors or even what it is in related species. Similarly we don’t call human hands flippers because that’s what the structure started out as even further back and it’s still preforming that function in modern fish.
The human visual cortex is larger than most creatures entire brain, it’s a wildly different structure than you find on a frog which plays a wider role in cognition than just decoding vision.
Putting this particular theory aside the generalization that evolution is a nested hierarchy of structures is pretty obvious on the macroscopic level. Traits like breathing oxygen, having symmetrical bodies, backbones, limbs. These are all examples of structures building on top of one another sequentially and conserved across species. Sure each of these subcomponents continues to specialize but the core functionality remains largely the same.
Going back to your analogy saying visual cortex of frog is wildly different from a human visual cortex. That's similar to saying a frog backbone is wildly different from a human backbone. Sure that's true but there's also a shared common core functionality largely conserved across time
Again the issue is the theory is misleading. Those traits are conserved through evolution largely because they’re useful, but if you look at say owl skulls you find wild asymmetries because that’s more useful even our lungs are very different from each other. Hagfish lost backbones and snakes lost limbs because nothing is sacred to evolution.
So yes frogs and humans both have a visual cortex, because we both have eyes. It really doesn’t explain anything beyond that point. The human visual cortex doesn’t even map to the same structures as it expanded into nearby ones.
>It really doesn’t explain anything beyond that point.
I think taking a macroscopic view like this points at interesting types of analysis. Evolution is analogous to a hill climbing algorithm navigating towards local optima in a probability field. Macroscopic evolutionary trends give a low resolution peek into the underlying probability distributions.
Frogs, birds, etc have very distinct spherical visual cortexes. Humans and squirrels don’t have that kind of spherical structure. So, other than naming where vision is processed the same thing the overlap isn’t particularly strong even at the most basic structural level.
It’s perfectly reasonable to extrapolate from studied organisms to species that share recent common ancestors. But reptiles don’t represent the probability distribution, they represent different results from that distribution under different evolutionary pressures. Extrapolation backwards and our common ancestor was very different from all decedents.
How exactly is this theory useful? Yes, frogs and humans process visual information because they both have eyes. That’s about all those structures have in common.
For nearly all of human history everyone thought that those frog vs. human eyes were completely separate and designed by some magical being living up in the cloud.
By noticing that while they have significant differences, those structures also have significant similarities, we were able to correctly answer one of the greatest questions of all time: where did humans come from?
To be useful models must accurately represent some aspect of reality, Reptiles don’t represent the brain of our common assessor particularly well. So this model is just wildly wrong without any predictive power.
Compare the giant spheres used by snakes, bird, frog etc to process visual information and try and map that to a rodent, bat, or human. Hint you’re not going to be able to locate an obvious sphere because the fundamental morphology is just different. You can say we both have areas of the brain devoted to processing vision but so do fruit flies.
Being reasonably conserved has minimal predictive power. Yes, knocking it or a closely related gene out out harms eye formation in a wide range of species but it says little about what specific structure ends up being formed.
- The superior/inferior characterize actually is part of the triune model, Maclean's book is replete with language like "advanced" vs "primitive".
- The point of the criticism is not that the neocortex is not a "layer" at all, but that it is not the case that if you were to remove the neocortex layer, you would essentially get the brain of a lower-order animal--but this is what is implied by the triune theory.
> The six-layer cortex appears to be a distinguishing feature of mammals; it has been found in the brains of all mammals, but not in any other animals.
What it evolved out of is entirely irrelevant -- everything evolves out of something else in some fashion.
While the neocortex does have distinct layers, the neocortex itself is not “layered” around the rest of the brain - it’s deeply integrated all over the place with the rest of the brain and nervous system. There is no hierarchical relationship between the neocortex and different systems it integrates with.
The reptilian equivalent to the neocortex is the dorsal ventricular ridge which evolved separately and in parallel. This presents two problems to the hypothesis: first the much simpler DVR serves much of the same purpose as the neocortex which was completely unknown at the time and second the most interesting bird species (the smartest ones) often don’t have an equivalent structure at all. There isn’t even a clear relationship between intelligence, complexity, evolutionary age, etc. After 250 million years of evolution any similarities are accidents of random convergence.
Also, it's not clear why we should accept that the brain would develop with locked-in "old strata" to a degree that we do not see in all sorts of other organs and systems.
As much as people joke about having a separate stomach for ice-cream, I've never heard anyone suggest that their "lizard stomach" would handle certain foods.
Because the brain physically, anatomically, has these "old strata". Lizard brains are pretty much just a basal ganglia. Humans have a basal ganglia, and then extra stuff on top. Mammals, and only mammals, have a neocortex "strata" to their brain as well.
I am not qualified to argue for or against the Triune brain, but it seems easy to see why the brain is different from the stomach in this regard.
> Because the brain physically, anatomically, has these "old strata". [...] Humans have a basal ganglia, and then extra stuff on top.
IMO the key is distinguishing between these two ideas:
1. There is a gross anatomical structure that can be linked to ancient ancestors with certain characteristics.
2. Those structures in living creatures are somehow "not really modern" or are unusually tied to the needs or limitations of those ancient ancestors.
Consider your fingers: They originate from fin-bones ~380 million years ago, yet (unlike "lizard brain") nobody talks about possessing "fish fingers" except as a fried food product. We also don't create narratives explaining our finger operations or design in terms of what ancient fish required or were capable of.
The Pterodactylus flying lizards are named literally for their "winged fingers". I suspect that we talk about this stuff when discussing evolutionary biology just fine, it's just that the "lizard brain" is a popsci term that the great-unwashed have latched onto.
In addition to this... Sure, evolution modifies existing structures, but if you compare a cat's heart and stomach to a pig heart and stomach, the difference is not that big, even though the nearest evolutionary ancestor was tens (hundreds?) of millions of years ago. Once a structure is in place and works well, you can certainly tweak it, but it's easier to mostly just keep it.
Humans have a neocortex, but if you play with a cat or dog, you can recognize and understand the emotions they are feeling. Fear, anger, joy, anxiety, relaxation, etc. That suggests the structures responsible for those things in us are probably not that different from them.
> Humans have a neocortex, but if you play with a cat or dog, you can recognize and understand the emotions they are feeling. Fear, anger, joy, anxiety, relaxation, etc. That suggests the structures responsible for those things in us are probably not that different from them.
And yet birds don't have a neocortex, and yet they share all the same behaviors that mammals share (at least in some species). I don't know if there is some creature with a neocortex that doesn't share all of these behaviors, but at least we can see that the neocortex may be sufficient but is not required for a species to have them.
Agreed. Mammals don’t even have the same metabolic strategy as reptiles - we’re endothermic while reptiles can’t even self regulate body temperature. Other systems fundamental to life like our reproductive strategies are also completely different.
The idea that major organs are strictly conserved over 250 million years while something as fundamental as homeostasis drastically diverges is frankly a bit wackadoo.
> evolution of the brain always happens by modifying the existing structure
Hmmm, my impression was that evolution took an existing structure and stuffed a bunch of new functionality into it, making it much larger and more complicated. Although the structure already existed in some form, it didn't have the same function. I think it's reasonable to think of this process as "adding" something, even if the structure itself is not entirely new. And human brains pretty clearly _are_ more intelligent than reptile brains!
Here's an analogy: Ancient organisms had light-sensitive "eyespots", and many of our distant cousins on the evolutionary tree (e.g. present-day flatworms) still have eyespots. Evolution gradually modified these existing structures into eyes. I think it's reasonable to think of eyes as a "new" organ that humans have and flatworms don't; and our eyes are clearly superior to flatworms' eyespots.
Evolution and adding complexity aren't the same thing. For example, evolution can also work in reducing complexity. Animals that spend generations living underground in caves will lose their eye sight over a long enough time period.
Point being its not about adding, it's about adapting
In _this_ case, the case of the human brain, I think it's fair to say that evolution started with the reptile brain and added something (even if that "something" is "new function and complexity" rather than "a completely new physical structure").
I agree there are other cases where evolution removes/simplifies things. Evolution is adaptation, and that adaptation can consist of adding, changing, and/or removing.
Eyes are far superior to eyespots in certain ways (accuracy, for one), but far inferior in others (energy consumption, size, durability). They are newer than the eyespots of the last common ancestor, but they could well be older than the eyespots of some flatworm species alive today.
"As I understood it, their point was that evolution does not add new layers, evolution of the brain always happens by modifying the existing structure."
The human brain is a highly complex set of distinctive organs. Saying there are different types of brains forming the human nervous system is literally what the biology teaches us.
Humans have this ability to obfuscate any issue. When there is a simple pattern for things some people always take edge cases and argue that the pattern is really not true. They don’t understand how models of the world work. Of course it’s not ideal but it’s a useful framework for understanding things.
I imagine the reason Newton’s laws never developed before was because of all the influential know-it-alls who took empirical data (moving objects stop! Gaseous balloons rise!) and drew the wrong conclusions from it (gases want to rise up to be with all the other gases…solids want to be at rest.)
It took Newton to do a thought experiment of a projectile moving in outer space to deduce his laws of motion.
The fact is that newtons laws aren’t really observable on earth, unless you have the imagination to see it and do the mental bookkeeping of accounting for friction as a separate force.
The triune model of the brain is not just a simplification, but one that promotes antiquated biases about human intelligence in how human intelligence differs from non-human intelligence, how intelligence is distributed among humans themselves, and what is essential to defining human intelligence itself.
The lizard, small mammal, human distinction maps pretty deceptively onto Aristotle's distinctions between the souls: vegetative (plant), sensitive (animal), and rational (human). So if one is trying to pinpoint the seat of intelligence, it seems to follow that we can ignore the two lower sections of the brain in favor of the higher one. Franz Joseph Gall, the founder of phrenology, himself did that, writing off the cerebellum as relevant only for producing the sexual drive [1].
Scientific theories of self-control which were nothing more than Christian dualist arguments evolved out of Gall's work and argued that intelligence involved suppression of the lower faculties, which provided cover for eugenicist and supremacist arguments throughout the 20th century and still shows up today in popular theories about how the 'limbic system' subverts the rational capacities of individuals and is used to manipulate the masses (Elon loves this theory).
Current work funded at the intersection of artificial intelligence and neuroscience still prioritizes the neocortex as the seat of rationality, with some like Jeff Hawkins (Palm founder turned brain scientist) arguing that "intelligence is an algorithm found in the neocortex". Singularity arguments rely in part on the assumption that intelligence in humans is mostly limited by the other parts of the brain, not empowered by them, and that a form of intelligence freed of embodiment will inevitably exterminate those that are embodied by right.
The truth is, neglected sub-regions such as the "lizard" cerebellum actually contain the vast majority of neurons, have been shown to have evolved disproportionately larger within early hominins [2], and are theorized to be equally involved in abstract cognition as in bodily manipulation [3]. This is something of a paradigm shift that has only been able to take shape since the late 20th-century (through the work of Jeremy Schmahmann, Peter Strick and others[4]), even though hints of it have been present in the data since it was collected, and that's because of how compelling the triune brain model has been. Research in this direction can directly address mental illnesses such as schizophrenia, but it has to be funded first [5].
Your argument seems to mostly rest on the idea that people can "poison" a fundamental idea by misinterpreting it and drawing silly conclusions from it. It sounds like if I argued that "1 + 1 = 2 and therefore we should do genocide", you'd be (rightly) abhorred by the conclusion, and the next time you saw someone using 1 + 1 = 2 as the basis for a completely different argument, you'd villainize them as using an argument that "promotes genocide" or "has been used to justify genocide". I really don't care what the founder of phrenology thought, nor Christian dualists, nor even Jeff Hawkins.
In general I think this effect contributes to a lot of "over-debunking". We see way over-simplified, yet very loosely accurate, mid 20th century scientific models like the triune brain, "ontogeny recapitulates phylogeny", the left-brain vs. right-brain, and the idea that differences in language contribute to differences in cognition; and then silly people take these models way too far and use them to justify dubious things; and then they become over-debunked to the point that speaking them aloud immediately ostracizes you as some outdated bigot; while the whole time the models themselves have been reasonably OK high-level starting points for discussion that obviously need revision for any lower-level details.
> The truth is, neglected sub-regions such as the "lizard" cerebellum actually contain the vast majority of neurons, have been shown to have evolved disproportionately larger within early hominins [2], and are theorized to be equally involved in abstract cognition as in bodily manipulation.
The relative number of neurons is not evidence for or against the model, nor the fact that they were larger in early hominins. Showing their involvement in abstract cognition is more interesting, but that's only evidence against the triune brain if you make the exact same mistake that you're criticizing, which is assuming that "abstract cognition" is some high-level uniquely human (or primate) trait. If that exact "abstract cognition" also exists in reptiles and birds (and it appears to), then the fact that the cerebellum contributes to that cognition is not evidence against Triune Brain.
> We see way over-simplified, yet very loosely accurate, mid 20th century scientific models like the...
I think its important for people to also spread the idea that "this is known to not be correct". Bad mental models continue to proliferate for generations (bad here not being a value judgement but rather of their known incorrectness and lack of predictive power).
It's like when you tell people that the alpha/beta dynamic amongst wolves came from one flawed study that has not been replicated and shown to be false many many years ago now. Same with "learning styles" research. Its difficult to approach the subject in a way that doesn't cause people to get defensive sometimes - they like the simplistic model which may once have been a fine point for a beginner but they got stuck in it and it can impair their growth and understanding.
It's fine for a layperson to walk around believing whatever they like - its likely closer to the truth than whatever they might otherwise have thought, or at least got them thinking. It becomes a problem when people actually base decisions off these things.
Is the simple metaphor of 3 layers in the brain equivalent to saying gasses want to be together and solids want to rest?
I think part of the debate in the comment section is on what kind of order / pattern we are trying to capture with the analogy. Does it make more sense to be analogous to the structural observations, or a more functional equivalency?
You could say an ocean is like a desert in that they are vast and empty with respect to surface structures observed by a human traveller, but obviously from a functional /environmental perspective the two almost couldn't be more dissimilar
> They don’t understand how models of the world work. Of course it’s not ideal but it’s a useful framework for understanding things.
Based on the rather casual way the author is using language in this piece, I'd bet that the researchers forgot that what they are describing are (nested) model(s) of reality...or that that level of precision is "pedantic" (the consequence being the confusion in this comment section).
> we have a basal ganglia which evolved from reptiles
And do living reptiles, today, not also "have a basal ganglia which evolved from reptiles?" seems we've a name collision, here. Perhaps we should refer to our ancestors as "proto-reptiles," or else our contemporaneous cousins as "post-reptiles" whose brains have had just as many years' time to depart from our common reptilique ancestor.
> Synapsids[a] are one of the two major clades of vertebrate animals that evolved from basal amniotes, the other being the sauropsids, which include reptiles (turtles, crocodilians and lepidosaurs) and birds.
> the only extant group that survived into the Cenozoic are the mammals.
> The animals (basal amniotes) from which non-mammalian synapsids evolved were traditionally called "reptiles".
> It is now known that all extant animals traditionally called "reptiles" are more closely related to each other than to synapsids, so the word "reptile" has been re-defined to mean only members of Sauropsida (bird-line Amniota) or even just an under-clade thereof
> "The triune brain hypothesis doesn't seem "wrong", it just seems like a simple categorization that is useful to the layperson."
Yes. Anything this simple will be wrong. Almost everything you learn in school before graduate level courses will be wrong. Most of it won't matter to you unless you start working in that field.
[1] is a nice book that explains in the first chapter why all science is wrong and gets replaced by a less wrong model, in steps. In fact the author argues that all those wrong models are perfectly fine and usable, for their period of time and applications.
> Almost everything you learn in school before graduate level courses will be wrong.
From what I understand, in many fields its pretty clear that most of the stuff in graduate courses is, too, its just that then next step toward right is less clear and more disputed than for the earlier wrong stuff.
No, your self-appellation aside, you are not missing anything unless there is some really secret 'nuance' hidden in the paper.
If the triune brain model was completely false (as stated by the caricature of "brain is not an onion with a tiny reptile"), it would not be straightforward to even identify the neocortex -- how do you know it is 'neo', what is it a 'neo' of and so on?
So the fact that we can meaningfully talk about these areas of the brain suggests that there is in fact continuity and building-upon happening in our evolutionary journey, although of course it's not like the cartoon they show (which I have never seen before from anyone seriously talking about this topic, I might add).
> If the triune brain model was completely false (as stated by the caricature of "brain is not an onion with a tiny reptile"), it would not be straightforward to even identify the neocortex -- how do you know it is 'neo', what is it a 'neo' of and so on?
This is a sort of proof-by-etymology and it isn't very persuasive. We have all kinds of words that derive from misunderstandings that have stuck, even long after the original misunderstanding was resolved. The geographical equivalent of this would be to say "we call them Indians, so they must have originated from India at some point!"
It's entirely possible that as our understanding of the brain evolves, this layered-over-time model will be seen as a quaint misunderstanding, but we'll still use the original names for the sub-organs because there's too much inertia to change them.
> If the triune brain model was completely false (as stated by the caricature of "brain is not an onion with a tiny reptile"), it would not be straightforward to even identify the neocortex -- how do you know it is 'neo', what is it a 'neo' of and so on?
I don't think that the intention of the article is to say it's completely false. It's that there is no neat evolutionary separation between the different parts of the brain. The "reptile" brain in humans is not truly the brain of a tiny reptile. We inherited a similar structure, but it evolved with us just like the rest of our brain.
The same goes for the tiny reptiles we see today, their brains also evolved alongside them. If we truly had a tiny reptile inside our brain then logically we could simply study the behavior of tiny reptiles if we wanted to study that part of the human brain. Which is probably the kind of misconception the authors of the article want to refute.
> we have a basal ganglia which evolved from reptiles
I took this as the key point addressed in the introduction—this model of evolution is widely understood to be wrong. We did not evolve from reptiles, we evolved alongside reptiles from a common ancestor. Modern reptile brains have also changed in form and function since our common ancestor, and we don't have whole divisions of the brain that exist in humans but not in reptiles.
Essentially, the triune brain theory goes right alongside that classic image of the monkey evolving into a man. It's not actually how evolution works, but it's a catchy simplification that's hard to get rid of.
From the caption to the first diagram:
> The evolutionary tree (c) illustrates the correct view that animals do not linearly increase in complexity but evolve from common ancestors. The corresponding view of brain evolution (d) illustrates that all vertebrates possess the same basic brain regions, here divided into the forebrain, midbrain, and hindbrain. Coloring is arbitrary but illustrates that the same brain regions evolve in form; large divisions have not been added over the course of vertibrate evolution.
If you want a detailed argument see Chapter 2 of Pierre Gloor's "The Temporal Lobe and Limbic System" where he argues against the (unfortunately still common) paleo/archi/neocortex terminology in favor if the allo/meso/isocortex terminology in the context of describing comparative anatomy. It is out of print but the Internet Archive has it available to borrow:
Your "isn't it true" paragraph is all incorrect (unless it is considered in a uselessly general way). For instance, Gloor notes that all mammals have an isocortex (that seems to have started in olfactory cortex). The "reptiles" that humans evolved from is just a catch all terminology for a diverse group of life and not closely related to current reptiles. He starts the chapter noting that ancestral brains are not available for direct study.
Looking at this as an amateur, it seems like the key question here is "does the human brain have substructures that are similar enough to brain structures from ancestral species that it makes sense to consider them as the 'same' entity with the same name?"
It's not TFA's actual thesis, but here's a _much_ more powerful rebuttal of the triune brain and similar mental models if you're interested (from the perspective of what is the sheer idea of rationality) Matthew Boyle's "Tack-on Theories of Rationality": https://dash.harvard.edu/bitstream/handle/1/8641840/Additive...
> But all of that seems rather obvious, and doesn't really refute the triune brain theory at all.
> The triune brain hypothesis doesn't seem "wrong", it just seems like a simple categorization that is useful for making big-picture distinctions.
Right, but having worked in the field, I can assure you that there are, in fact, too many practicing psychologists, cognitive scientists, and even neuroscientists who believe the triune model of the brain to be literally and, sometimes, absolutely true. These are the types of people whom the linked paper is trying to reach.
Misunderstandings based on these oversimplified models are driving the current debate around modular versus distributed computation in the brain[1]. Obviously, a more accurate model of the brain would account for both ideas, but there is growing concern in the neuroscientific community over the amount of grant money going toward defending older, dead-end modular models instead of improving newer, more promising distributed models, mostly as a result of entrenched interests prioritizing the maintenance of prestige over the pursuit of truth.
In short, putting bad models on blast is good and necessary for the advancement of science. You can get a lot done with the plum pudding model[2] of the atom, but you can get far more done with the Bohr model[3] which emerged only after Rutherford, Bohr, and several other physicists published several iterative takedowns of the former, and yes, they too had to deal with entrenched interests who operated under the assumption that the plum pudding model was literally and absolutely true. It took a decade of experiments and several increasingly correct models before academic consensus shifted enough to accept the existence of subatomic particles and academic consensus began its collective investment in quantum mechanics. We're now in a similar place with neuroscience in the tension between modular computational models, which includes the triune brain model, and distributed computational models, which are showing promise in rescuing fMRI studies with their strong modular tradition from the replication crisis[4].
Thank you for your contributions. Am I correct that you are asserting there are substantial numbers of practicing psychologists that literally and absolutely believe inner structures of the brain are unchanged over hundreds of millions of years, and they can and will be reached by this paper?
If anyone doesn't understand "All models are wrong, but some are useful" I don't know if you'll reach them with this paper.
Maybe it needs to be said. It's possible the most useful papers are those that assert obvious things in ways that refute our basic models so we can see things differently. It's also possible this is a clickbait paper that isn't saying anything new, just trying to be controversial.
This article is simply based on an uncharitable interpretation of the triune brain model. Literally nobody I know in the field believes in the cartoon-like description given by the article, and none of my introductory textbooks (I have quite a few which touch on this, from embryology to biopsychology to neuroanatomy) explain it in such a silly way as in the article.
The title definitely seems like a strawman, but it is the best use of a strawman that I've seen in an academic article: an outrageous and amusing title that makes me want to read the paper!
(The rest of the article seems much more defensible to me: well-written without quite verging into strawman territory. But I'm no expert in the field.)
Especially since the master reptile - the adrenal cortex - is located atop the kidneys. Fight or flight is first an electrical relay to the hands and feet and heart. The brain in the skull and consciousness reflects upon what’s already happening in the periphery.
It is also super important for everyone to understand that. Because our body is not "brain -> body control" most of stuff just happens and brain reacts.
For overall health it is also important to understand that body needs movement and all neural pathways are also somewhat independent and also contain "intelligence".
I am not neurobiologist so hope I am not going into mumbo-jumbo too much but I workout at the gym quite often and can observe over-training or how muscles often could still work but your neural pathways are done and you cannot hold the weight even if muscle/tendons feel quite fine on its own.
It is also quite common knowledge as I read on the internet stuff on training.
So in the end I don't feel body-mind separation is useful as much and thinking that your whole body is also ones mind is super important.
One thing that people need to realise that you can use your body to trick your mind into doing things.
If your brain is anxious, you can consciously use breathing techniques to trick it into thinking you're calm. Box Breathing for example works pretty well. Or just taking 2-3 really deep slow breaths.
An anxious/nervous brain defaults to short shallow breaths for some reason.
> The brain in the skull and consciousness reflects upon what’s already happening in the periphery.
I've read summaries of these studies as well, but... the adrenal cortex doesn't have any sensory-processing facilities, right? In the end it's the brain that informs the adrenal gland?
The truth is somewhere in between. The adrenal cortex responds to signals from the brain which responds to the hormones from the adrenal cortex. It's the interplay of mind and body that influences our perception of reality.
It may not be true from the perspective of evolutionary biology. But 90% of the time I've heard this referenced (our "primitive brain") it's a useful device for discussing the parts of our psychology we have in common with more primitive members of the animal kingdom. That's not to contradict the article whatsoever, which is explicitly addressed to psychologists who, I concur, should be educated and clear on the distinction between a rhetorical device and real biology.
The autonomic nervous system is real biology that most psychologists don’t start with. While this article is based on textbook descriptions of the evolution of the brain in the skull, not seeing much on how the autonomic nervous system is primal specifically for survival.
I'd be more inclined to agree if it weren't an increasing issue in my life that laymen do not understand they're parroting back a rhetorical device and use this information to make all kinds of ridiculous conclusions.
Increasing? This has always, and will always be an issue. My approach is to roll with it - rather than banish them altogether, I treat all devices like this as such and no more, holding others to the same standard. This, hopefully shifts the meaning away from the scientific and towards the domain of “quaint sayings.” For instance, I invoke the concept of the “lizard brain” quite commonly as a way of expressing how base instincts can override my better judgement. But I’m careful to never imply there (in the words of the article) “a scala naturae view of evolution in which animals can be arranged linearly from ‘simple’ to the most ‘complex’ organisms.”
At most any model can describe some part of reality with a given validity. Some models don't have any region of validity so we shouldn't use them. I think saying that 'all models are wrong' is kind of, rhetorical rather than instructive.
Donald hoffman says something exactly like that in this talk. David Bohm came the same conclusion science will never fully figure it out the answer is much spiritual and imaginative
Why? because ultimately we are talking about a empty field of space propagated by light, similar to holograms. Things that grow here things that stem from this world do you think they really are what they appear to be? Of course not. So what are they god damnit? perhaps its better to not answer the question and like a good old mystic leave it be and open a portal to another dimension and have this experience for one self
The errors/issues here are much higher in the stack than what Hoffman and Bohm are getting that at the levels you note, though Bohm in addition to that also spoke a lot about language and communication (which is an important part of the issue here).
For all the good work he did, this is the one misstep in Sagan's career that likely caused the most disruption: he was big on the "reptile brain inside a mammal brain" hypothesis and described it quite convincingly on Cosmos.
We don't have a great strategy yet for undoing the work of an effective science educator when they teach things science goes on to disprove.
So now we've learned what brain is not - but what is the biologically/evolutionary correct model that explains the opposite impulses that we all are dealing with? And why some of those impulses need willpower and grow weaker under the influence of stress/alcohol/drugs, while others seem to grow stronger?
Three-brain structure (Freud's id, ego, superego) is still the best simple explanation I know. Maybe the physical reality is a bit different, but it partitions actions so nicely.
Id - base impulses, bubble up automatically and subconsciously
Ego - the self, the "me". Where the story of identity comes from, what gets judged in court.
Superego - rules imposed from on high that restrict behavior
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I think "opposite impulses" can be explained as a form of self-control. Let's say I see someone I'm attracted to, but want to maintain composure and stay in a neutral stance. Left to my own devices I'll flush, and my eyes will widen, maybe I'll get clumsy. Bringing an opposite-but-aligned emotion in maintains equilibrium (anger, disgust...)
I see opposite-but-aligned impulses with my dog all the time. He knows I don't like him chasing squirrels. When he sees one, he gets activated + alert, but redirects his energy into running a few paces the other way. It's a bridge between the id (Go! Chase!) and the superego (Stay calm, don't pull!)
Interestingly, Freud's model is very similar to Plato's tripartite soul from the Republic with the appetites, the "spirited" part of the soul, and Nous, and Aristotelian psychology has the same tripartite soul. The big difference is the modern view of superego vs the ancient view of nous are quite distinct.
You don't need to. 'Superego' is an invention. You could invent your own abstract idea and call it you. Or you could simply declare that the superego is you.
none of them alone is you. Thats kinda the point. You are all three. Maybe you were tempted to do something indulgent, but decided against it. Another brain might have made a different choice. On a different day, with a little more stress and tiredness, you yourself might have made a different choice.
There's a huge difference between simple and simplified. The whole purpose of the science is building the (more or less always) simplified models of the world, abstracting important concepts out of the chaos of real world so that we can reason about them easier.
I think it's easy to underestimate how different our brains are relative to different classes of animals, and there is a lot of convergent evolution going on.
For example, even low level auditory perception, such as how the brain evolved to localize sound directions, evolved independently in mammals and birds: https://journals.physiology.org/doi/full/10.1152/physrev.000... (this is because their common ancestor didn't have a tympanic ear).
So the Triune brain really isn't the best model for explaining what is going on in the brain. Models such as reinforcement learning don't fully explain what is going on in the brain either, but I think explanations such as how dopamine flooding the reward system can mess with predicted rewards and contribute to addiction, etc. are more useful.
Not that the opinion of some random on the internet means anything, BUT....
I think the neocortex for the most part lets other parts of the brain control themselves... and really only has high level access. I think emotions are one of these lower level semi autonomous subsystems... but so are things like autonomous body control, balance, each of the senses etc, etc... The neocortex is playing the "Human" video game and controlling things from a high level... but cannot directly control every aspect of these subsystems... and honestly, this is how complexity is dealt with (if the neocortex could control it all, the whats the point of the other subsystems)?
I feel like the "lizard brain" thought-paradigm can actually be understood as communicating something true/useful/important... but it'll only make sense to people with a good understanding of "speciated evolution": namely, evolutionary biologists themselves; and software engineers who've worked with programming languages that use prototypical inheritance. Outside of those two groups, the actual "intuition" for what the claim is saying, gets lost.
The "lizard brain" claim, as far as I understand it, was never that you have a complete copy of a "lower" brain inside your brain. Nor even that you have specific structures within your brain whose implementation was evolutionarily conserved.
Rather, what I understand the "lizard brain" claim as trying to communicate, is that you have one or more components of the architecture of your brain, where the APIs presented by those components to the rest of the brain, have been mostly conserved throughout evolution. The components themselves may have internally evolved, but the structural boundaries between those components and the rest of your brain have stayed stable in a way that allows biologists to recognize those same components in the architectures of brains in vastly different species.
To put that in concrete terms: you and a mantis shrimp both have e.g. "an amygdala." The gene code for "an amygdala" may have differentiated between the shrimp and you, but there's still a conserved part of the brain's architectural plan that says "put an amygdala here."
Now for the overwrought OOP analogy:
If you imagine HumanBrain as an OOP class, then it's an OOP class that is a subclass about 800 layers of inheritance deep; with the root of the inheritance hierarchy being some prototypical bilateral-vertebrate nerve-cord class.
In this inheritance hierarchy, each layer can introduce new "features" — components of the brain that have specific APIs; in other words, members of the class with known interface types, that other parts of the class can have their implementations — but not their own APIs — altered to work in terms of.
Under this mental [heh] model, the "lizard brain" claim isn't about the LizardBrain level of the hierarchy itself; but rather is that one or more brain features seen in the HumanBrain class, are features that were introduced in or around the LizardBrain level of the inheritance hierarchy, and whose APIs have stayed stable ever since.
(Also, if you're wondering if any real-world computer software has ever done 800-layer-deep inheritance hierarchies such that it starts to actually reflect this kind of speciated evolution: yes! The programming of https://en.wikipedia.org/wiki/LambdaMOO was exactly like that. Why? Because, unlike a regular codebase, but like evolution, LambdaMOO was a gradual accretion of private objects "owned" by amateur coders, where each dev would implement the features they cared about by finding someone else's object with that feature, and forking it [i.e. prototype-inheriting from it] to suit their own needs. There was no common codebase that anyone could refactor, so it gradually came to resemble an actual biological process.)
I have not read the paper yet, but what a great title - a very welcome change from the formulaic 'verbing the noun: towards a metastatic model of semantic construction' that has become so widespread over the last couple of decades.
The inarticulate abstract was a red flag. I read 2/3 of the paper before giving up when finally, after untold quantity of adjectives, assertions, and halfway through, the supposed first couple of arguments made an appearance and were mostly indecipherable as such. The paper reads like what a high school junior thinks that a research review(?) is supposed to look like. Also, it is clear to me that the authors began with a conclusion around which they attempted to wrap support. The psych field needs low quality papers like Alaska needs snow.
* Widespread misconceptions:
a) "Newer" brain structures were added on top of "older" brain structures.
b) The "newer" brain structures provide more complex functions.
* Psychologists have been publishing these in textbooks.
* Neurobiologists have known these to be wrong for some time.
The core statement of the abstract is that the author's conclusions are the "clear an unanimous" views of "those studying nervous system evolution".
This statement is incorrect on its face. Worse, it would be a bad scientific statement in any paper. Last, it is at once superfluous and incomplete even if it were true. Instead, a good abstract would briefly list the points of the author's preferred theory rather than waste the reader's time by only deferring to a loosely defined general authority in support of an assertion. Which is abstract writing 101, at least in fields for which writing standards are somewhat kept. Maybe that isn't the psychology field, but it should be.
The last sentence of the abstract reads as if written by said high school junior. Science authors generally don't use the word "mistaken" to describe another theory, especially in the context of theories of brain evolution nor for anything else for which literally every theory can only be a theory. Including that preferred by the author.
Good papers don't introduce their arguments / pov halfway through, or further. Good papers don't lean on deference to authority 1/2 paper before presenting what is supposed to be their evidence or theory. Good papers almost completely exclude adjectives when describing theories, conclusions, or data, let alone negative adjectives that are doing all of the work in making their yet-unsupported point.
I especially like surveying textbooks over time, to call out the originators of misconceptions, and the lazy copy pasta cohorts who followed their lead.
The misrepresentations are particularly egregious in neurophysiology, which should be a very concrete observational science, based on dissections of many species in the context of evolution.
Perhaps Just So pop-sci evo-psych theories have their reckoning with scientific reality ahead of them.
I can think of it like the wheels are still there, the frame, engine, body etc but the design and materials have been completely refined and overhauled to be modern future tech today. The car even has new stuff like electronics and wifi. Meaning there are still base conceptual things there but they are not the same...knowing that reasoning by analogy is flawed but still satisfying to me to feel like I understand it enough.
There's quite an interesting analogy there. I guess you could have a four wheeled wagon structure similar to wooden wagons of old, then an engine added and now electronics added, as an analogy to the triune brain. It's not that modern cars are built on wagon chassis but that the basic body with four wheels structure is similar for functional reasons. Probably similarly with the 'reptilian brain.' Our bits are maybe similar because they do the same job rather than because they evolved from that.
> article that claims to debunk something that nobody said
About a third of the article was dedicated to who said it and when:
>> As Paul MacLean (1964), originator of the triune-brain theory, stated: man, it appears, has inherited essentially three brains.
>> This belief, although widely shared and stated as fact in psychology textbooks, lacks any foundation in evolutionary biology.
>> The most widely used introductory textbook in psychology states that: ... The brain’s increasing complexity arises from new brain systems built on top of the old, much as the Earth’s landscape covers the old with the new. Digging down, one discovers the fossil remnants of the past
>> we sampled 20 introductory psychology textbooks published between 2009 and 2017. Of the 14 that mention brain evolution, 86% contained at least one inaccuracy along the lines described above.
>> For example, Dijksterhuis and Bargh (2001), [...] write that: when new species develop, this is done by adding new brain parts to existing old ones
>> Examples of MacLean model of brain evolution appear in other areas, including models of personality (Epstein, 1994), attention (Mirsky & Duncan, 2002), psychopathology (Cory & Gardner, 2002), market economics (Cory, 2002), and morality (Narvaez, 2008). Nonacademic examples are too numerous to fully review.
>> Carl Sagan's (1978) Pulitzer Prize-winning book, The Dragons of Eden, and Steven Johnson's (2005) Mind Wide Open were both popular books that drew heavily on this idea
The quoted text give lie to the title. Nobody said it was an onion etc. Just that it was built new structures on old, all changing, integrated more or less well.
Not being pedantic, I don't think? The title is disparaging, deconstructing the idea to the point of ridicule. It's reasonable to say "Nobody said that!"
If the authors are going to classify colloquial language (3 brains) as literal, their own study is then open to the same attack, and there is plenty of material from even the short skim of it I did.
I think some people’s brains have trouble understanding the purpose and value of models (it’s their predictive power). For some use cases it doesnt matter of the model is “correct” so much as whether or not it has predictive value. I’m sure someone else here can phrase it far better than I.
> Does it matter if psychologists have an incorrect understanding of neural evolution? One answer to this question is simple: We are scientists. We are supposed to care about true states of the world even in the absence of practical consequences. If psychologists have an incorrect understanding of neural evolution, they should be motivated to correct the misconception even if this incorrect belief does not impact their research programs.
The hallmark of an incorrect model in science is that it makes incorrect predictions about the natural world (experiment). What incorrect predictions has psychology made based on the incorrect triune-brain theory?
I'm going to guess zero, not because the model works, but because psychology has made no experimentally testable predictions based on it.
> The hallmark of an incorrect model in science is that it makes incorrect predictions about the natural world (experiment).
Sure, if you are insular and only care about how it affects the field and other scientists.
Sometimes these incorrect models are incorrect in ways that are really attractive from a narrative standpoint. The hallmark of those models is to be used to spawn hundreds of pop science books that expound on those models in unfounded ways and push people into useless behavior, sometimes at a societal level.
Maybe scientists and psychologists aren't using the idea of a lizard brain in experiments and current theories, but I know there's at least some laypeople people that use it as a way to explain their behavior or make assumptions about other people's behavior, or to form their own ad-hoc explanations and models of behavior based on poor understanding of even what was previously reported to them. I would hazard it's actually more than some, and a lot of people do it, with this or some other poorly reported incorrect model of behavior or how the body works or how the world works.
Incorrect knowledge should be corrected. Leaving it it as it is leads to myriad problems, small and large, eventually.
Well said. Just because it may be hard to pin down the consequences of the wrong-but-attractive narrative, there probably are consequences, especially on the long term.
Is it really so surprising that these simplistic narratives don't actually accurately describe how the brain works? We should be prepared to admit that the brain is complicated and we don't really know it's functioning at a fundamental level.
Psychology can barely make any predictions. This isn't a meaningless technicality like the not-to-scale diagram of atoms used in old textbooks. Correcting poor assumptions to find new models of understanding is still important in this field.
The goal of cognitive science is to basically build the foundation (the understanding of how the brain works) that psychology lacks and is a field that psychologists are actively contributing to.
Ultimately, psychology was created as a pragmatic branch of philosophy with the understanding that we would not know how the brain works for quite some time but that we could still do something of value and help people.
Not just psychology. Even the claims within this very paper are hard to test. Anything involving evolution is almost impossible to test. The "science" is mostly observational and descriptive and arrived at through logical guesses.
If all of "science" involved strict rigor to the "scientific method" we'd have none of the social sciences like anthropology or evolutionary psychology.
This paper is simply pointing out differences in view points.
I think the general idea in psychology is real though, the paper gets into details which is a bit pedantic. In fact the paper literally states that they are all in agreement that all brains evolved from a common ancestor. This would be the "reptile" and for sure common features in our brain such as serotonin stem from this "reptile" brain.
Psychology gets a lot of bad rep for the reproduction crisis, but evolution should largely be worse because we can't experimentally verify anything without time travel.
So it's not like this paper is about true science defeating pseudo science. It's all really speculative.
The biggest I’ve seen is that talk therapies don’t work well if an underlying sleep concern is not addressed. Sleep as the parasympathetic nervous system is predictable from a more primitive model whereas a cognitive - behavioral model assumes thoughts can drive recovery.
I think there's a good chance you are right, but academically-minded people have a tendency to hastily dismiss hypotheses that run counter to what they believe is a correct theory. I can imagine someone dismissing the idea that a psychological pathology is related to a neurological one because the latter is in the "wrong" part of the brain for the symptoms the former presents.
edit: I was trying to jokingly reply "Yes {smiling-imp-emoji}" when I realized I've never seen an emoji on Hacker News before - looks like they get automatically removed!
Perhaps one distinction would be that ethics change across time and country. So it might be possible to run a test in 2020s UK that cannot be repeated in 2030s.
Scientific rigor has it's limits. Certain fields need to make intuitive leaps of speculation.
For example the entire field of astronomy is basically unverifiable bullshit. It's all speculation. We make guesses on what's going on with the stars outside of our solar system from twinkling light that comes from light years away.
Any science to verify the claims made by astronomy with the amount of rigor you demand would involve light speed space ships to go to those stars and verify.
If we could do this I think you'd find a ton of astronomy would be flat out wrong.
Nonetheless the field is still useful and legitimate despite the high likelihood a lot of it is wrong and despite the fact we can't verify much.
I'm surprised by how much this publication reads like an advocacy piece for a specific viewpoint, rather than an objective review of existing literature.
Just from reading the paper, it is clear that there are many experts in the field that take the opposing viewpoint that is being attacked in the paper, especially considering that their hypotheses have been published in widely circulated textbooks.
When it comes to research publications in general, I very much prefer to hear an objective, good faith presentation of the major viewpoints, with the author taking an opinionated but measured take in the conclusion as they review the overall weight of the literature. I'm sure there are issues with this "triune brain" model, but at a certain level every model is inaccurate; the real question is whether a model is useful in its framework, and the answer has a degree of subjectivity such that I do not think it is fair to categorically reject the perspectives of opposing experts in the field.
Well, the main problem with this is, it would require human experimentation to be efficient. You know, those babies raised in this way, those in that way. And by the age of 2 cut open and everything meassured.
Or do you have other ideas how to do proper testing?
Because otherwise experiments with control groups, electrodes, MRT etc. are a thing in psychology. But you can only achieve so much with it.
The study of psychology is done in neuroscience. But the research is extremely different. Neuroscience is like studying quantum mechanics and electromagnetism to understand the movement of electrons in a wire, while Psychology is comparable to UI/UX research.
Many people are working on bridging neuroscience and psychology but it hasn't happened yet.
Ok, I see (maybe formally wrong) neuroscience as a part of psychology. (At least some psychologists I talked to, had this position)
And the reason why bridging is not really happening, because of the ethical restrictions. But this is my hypothesis. The other hypothesis might be, that too many careers depend on models that would not hold up by experiments, but I really cannot judge here because of lack of knowledge.
Neuroscience is a subset of biology, Psychology seems to be its own field off in liberal arts (maybe under Philosophy?), borrowing reputation from Neuroscience and Statistics while often refusing to adhere to the tenants of a real science.
> Ok, I see (maybe formally wrong) neuroscience as a part of psychology. (At least some psychologists I talked to, had this position)
They might believe this in the same way that some UX people might view all of software as a subset of UX, because everything ends up as an experience for some user somewhere.
It’s more of the former - it’s not ethical to do the experiments that would prove or disprove the hypothesized links. There’s plenty of real work to do, not a conspiracy lol
BTW, is there something new and interesting about the connection between quantum mechanics and the brain? There are many articles/papers in [1] but it would be great to hear from someone in the field.
> Or do you have other ideas how to do proper testing?
Well, for starters don't call them studies, call them "hunches" or "intuitions" or whatever you like to indicate that there is actually no real evidence to prove your thesis.
Occam's razor tells us to believe that it's much more plausible that psychologist publish massaged data to keep getting funded, than because it's actually very hard to admit that "we don't know for sure, this study proves nothing".
Have you ever heard of my fellow Italian professor Francesca Gino?
Unless you want to start growing test subject humans in vats, it's not exactly something that's as simple as "testing right" — the problem isn't lack of will or skill. We can't just throw rats at this problem like many scientific fields do.
yeah, exactly, it's not real science. Doesn't matter why.
Atomic bombs are very dangerous too and not very easy to "test them right", but atomic physics is a real science.
Anyway, the problem in psychology is that psychologists often lie and fabricate false evidence, not that the rats aren't enough.
There are multiple studies about it, published by scientists, most of them agree that "Don’t trust everything you read in the psychology literature. In fact, two thirds of it should probably be distrusted."
There's a point where a field can't keep going on shielding behind the false myth that "the problem is that we can't test on humans".
Sorry if I misunderstood, it's just that at times "real science" is used to discredit psychology as a field entirely so there's a bit of defensiveness involved.
Exactly, and the irony is that there are a lot of cognitive neuroscientists doing human participant research all the time. It's honestly easier than doing the ethics for animal research these days. I don't understand all the comments from everyone saying it's impossible to do reliable research with human participants, haha.
"There are multiple studies about it, published by scientists, most of them agree that "Don’t trust everything you read in the psychology literature. In fact, two thirds of it should probably be distrusted.""
the real problem is that the kind of psychology studies that gets the more attention on the media, that shape the culture and the beliefs of the general public and that are often used by governs and institutions (even medical ones) to deploy policies, health care plans, school or work environment guidelines, etc. etc. are those that are less trustworthy, that fail to be replicated the most and more subject to interpretations and subjective biases, in particular social psychology (citation: Social Psychology (38% success rate, n = 256).)
Which is why it's not a real science. No one is saying that "scientists" working on psychology are negligent, but that it's impossible for psychology to meet the requirements of a real science.
I think it's a little harmful to start saying "real science" — this is something that is at times meant to discredit psychology entirely, so it's an unfortunately loaded phrase.
I think they're still doing science, it's just much more difficult given physical and ethical constraints.
You're missing the point that calling something "not real" is very often used as a method to discredit it. Saying "not real" discredits the fact that there are more barriers here.
That's my primary issue with this. Phrenology can also be called "not real science" but it doesn't seem fair to paint both with such a broad brush. There's more nuance involved than an off-the-cuff "not real."
Though at this point it all feels too belabored to carry on.
It's surreal to see so may people reading the article with this takeaway, the "What's Wrong" section seemed very clear to me and elaborated for a while including a number of citations on why the simplistic layer model was flawed.
> providing no supporting evidence
I checked, there's seventeen separate citations for evidence in the "What's Wrong" section as well as several figures.
In fact, this article seems to set it up as a bit of a straw man. The main rebuttals in this article are 1) that evolution is branched rather than linear, 2) that larger brains aren't necessarily more complex, and 3) that evolution modifies existing brain structures in addition to adding new layers.
But all of that seems rather obvious, and doesn't really refute the triune brain theory at all.
Isn't it scientifically true that we have a basal ganglia which evolved from reptiles, a limbic system also present mammals, and a neocortex that works similarly to that in other primates, dolphins, and elephants? And each of those map to certain types of behaviors, that we see in these species?
The triune brain hypothesis doesn't seem "wrong", it just seems like a simple categorization that is useful for making big-picture distinctions.
Am I missing something? I literally don't understand what is even being "refuted" here, because the refutations don't seem to match the claims at all.
[1] https://en.wikipedia.org/wiki/Triune_brain
As I understood it, their point was that evolution does not add new layers, evolution of the brain always happens by modifying the existing structure.
Which is why a "stratified" view of the brain with evolutionary older layers near the center and newer layers near the surface is incorrect.
The implications of this belief then led to incorrect assumptions about both humans and (non-human) animals: That the human brain is an "animal brain plus something else" and therefore automatically superior - and inversely that animal brains are "human brains minus something" and therefore automatically inferior. The article argues against both positions.
The triune model doesn't claim our brain grows additively in rings like trees. It's merely an observation about the primary evolutionary origins of the three parts. Just those three.
And the superior/inferior characterization is not part of the triune model. You are free to interpret it that way if you want, but it's not part of it, so it's not a rebuttal.
Not sure about reptiles, but the author write this about mammals:
> Neurobiologists do not debate whether any cortical regions are evolutionarily newer in some mammals than others. To be clear, even the prefrontal cortex, a region associated with reason and action planning, is not a uniquely human structure. Although there is debate concerning the relative size of the prefrontal cortex in humans compared with nonhuman animals (Passingham & Smaers, 2014; Sherwood, Bauernfeind, Bianchi, Raghanti, & Hof, 2012; Teffer & Semendeferi, 2012), all mammals have a prefrontal cortex.
I also read some interesting papers a few years ago about corvids - particular New Caledonian Crows: Those animals do not have a neocortex and hence were thought incapable of many higher-level cognitive tasks, such as planning, tool use, etc. Turned out the crows were in fact capable of them. One hypothesis I read suggested that, as crow brains are structured differently, another structure may have taken the role that the neocortex has in humans.
So even if it's an anatomical distinction, it's an unreliable indicator of mental capacity.
Literally nobody is claiming that only humans have neocortexes.
Nor is anyone claiming it's an indicator of mental capacity. The recent discoveries about crows were interesting, but that doesn't have anything to do with the fact that the neocortex in mammals plays a particular, functional, well-recognized role.
> The triune brain consists of the reptilian complex (basal ganglia), the paleomammalian complex (limbic system), and the neomammalian complex (neocortex), viewed each as independently conscious, and as structures sequentially added to the forebrain in the course of evolution. According to the model, the basal ganglia are in charge of our primal instincts, the limbic system is in charge of our emotions and the neocortex is responsible for objective or rational thoughts.
We disproved:
- the sequentially added nature
- what these zones are responsible for
So in the end we're only left with a semi-arbitrary split of the brain in 3 zones and none of the hypothised implications. That to me refutes the hypothesis as a whole, and we're keeping the zone naming by sheer inertia.
The correct view is that while the neocortex is indeed mostly new, the “older” more central structures were modified throughout evolution.
This argument is akin to saying we're not "newer" apes ala
> The refutation is of the idea that it’s a strictly chronological ordering of species, with the old species still inside and intact. The correct view is that while homosapiens are indeed mostly "newer", the “older” apes were also modified throughout evolution
Obviously.
> As Paul MacLean (1964), originator of the triune-brain theory, stated,
>> man, it appears, has inherited essentially three brains. Frugal Nature in developing her paragon threw nothing away. The oldest of his brains is basically reptilian; the second has been inherited from lower mammals; and the third and newest brain is a late mammalian development which reaches a pinnacle in man and gives him his unique power of symbolic language.
And they quote other textbooks that are making claims along these lines too; this is right at the beginning of TFA. So I think you are wrong that “no one thinks that”.
Of course they don’t think the old brains are 100% static but there are claims that they are largely conserved.
That they're not static doesn't necessarily mean that they aren't largely conserved.
Modern reptiles, birds, and humans have experienced the same amount of evolution. There’s similar traits, but we don’t call whale flippers hands because that’s what the structures was in some of their ancestors or even what it is in related species. Similarly we don’t call human hands flippers because that’s what the structure started out as even further back and it’s still preforming that function in modern fish.
The human visual cortex is larger than most creatures entire brain, it’s a wildly different structure than you find on a frog which plays a wider role in cognition than just decoding vision.
Going back to your analogy saying visual cortex of frog is wildly different from a human visual cortex. That's similar to saying a frog backbone is wildly different from a human backbone. Sure that's true but there's also a shared common core functionality largely conserved across time
So yes frogs and humans both have a visual cortex, because we both have eyes. It really doesn’t explain anything beyond that point. The human visual cortex doesn’t even map to the same structures as it expanded into nearby ones.
I think taking a macroscopic view like this points at interesting types of analysis. Evolution is analogous to a hill climbing algorithm navigating towards local optima in a probability field. Macroscopic evolutionary trends give a low resolution peek into the underlying probability distributions.
Frogs, birds, etc have very distinct spherical visual cortexes. Humans and squirrels don’t have that kind of spherical structure. So, other than naming where vision is processed the same thing the overlap isn’t particularly strong even at the most basic structural level.
It’s perfectly reasonable to extrapolate from studied organisms to species that share recent common ancestors. But reptiles don’t represent the probability distribution, they represent different results from that distribution under different evolutionary pressures. Extrapolation backwards and our common ancestor was very different from all decedents.
Every scientific model and analogy is flawed in some way, but many are still useful.
By noticing that while they have significant differences, those structures also have significant similarities, we were able to correctly answer one of the greatest questions of all time: where did humans come from?
Of all models, this one is particularly useful.
Compare the giant spheres used by snakes, bird, frog etc to process visual information and try and map that to a rodent, bat, or human. Hint you’re not going to be able to locate an obvious sphere because the fundamental morphology is just different. You can say we both have areas of the brain devoted to processing vision but so do fruit flies.
https://en.wikipedia.org/wiki/PAX6#Species_distribution
It would seem enough people did to warrant this person to write about the topic.
- The point of the criticism is not that the neocortex is not a "layer" at all, but that it is not the case that if you were to remove the neocortex layer, you would essentially get the brain of a lower-order animal--but this is what is implied by the triune theory.
It seems like this is what they are refuting. It is not so much a new layer as it is an evolution of existing structure.
https://en.wikipedia.org/wiki/Neocortex
It clearly states:
> The six-layer cortex appears to be a distinguishing feature of mammals; it has been found in the brains of all mammals, but not in any other animals.
What it evolved out of is entirely irrelevant -- everything evolves out of something else in some fashion.
The reptilian equivalent to the neocortex is the dorsal ventricular ridge which evolved separately and in parallel. This presents two problems to the hypothesis: first the much simpler DVR serves much of the same purpose as the neocortex which was completely unknown at the time and second the most interesting bird species (the smartest ones) often don’t have an equivalent structure at all. There isn’t even a clear relationship between intelligence, complexity, evolutionary age, etc. After 250 million years of evolution any similarities are accidents of random convergence.
As much as people joke about having a separate stomach for ice-cream, I've never heard anyone suggest that their "lizard stomach" would handle certain foods.
I am not qualified to argue for or against the Triune brain, but it seems easy to see why the brain is different from the stomach in this regard.
IMO the key is distinguishing between these two ideas:
1. There is a gross anatomical structure that can be linked to ancient ancestors with certain characteristics.
2. Those structures in living creatures are somehow "not really modern" or are unusually tied to the needs or limitations of those ancient ancestors.
Consider your fingers: They originate from fin-bones ~380 million years ago, yet (unlike "lizard brain") nobody talks about possessing "fish fingers" except as a fried food product. We also don't create narratives explaining our finger operations or design in terms of what ancient fish required or were capable of.
Humans have a neocortex, but if you play with a cat or dog, you can recognize and understand the emotions they are feeling. Fear, anger, joy, anxiety, relaxation, etc. That suggests the structures responsible for those things in us are probably not that different from them.
And yet birds don't have a neocortex, and yet they share all the same behaviors that mammals share (at least in some species). I don't know if there is some creature with a neocortex that doesn't share all of these behaviors, but at least we can see that the neocortex may be sufficient but is not required for a species to have them.
The idea that major organs are strictly conserved over 250 million years while something as fundamental as homeostasis drastically diverges is frankly a bit wackadoo.
Hmmm, my impression was that evolution took an existing structure and stuffed a bunch of new functionality into it, making it much larger and more complicated. Although the structure already existed in some form, it didn't have the same function. I think it's reasonable to think of this process as "adding" something, even if the structure itself is not entirely new. And human brains pretty clearly _are_ more intelligent than reptile brains!
Here's an analogy: Ancient organisms had light-sensitive "eyespots", and many of our distant cousins on the evolutionary tree (e.g. present-day flatworms) still have eyespots. Evolution gradually modified these existing structures into eyes. I think it's reasonable to think of eyes as a "new" organ that humans have and flatworms don't; and our eyes are clearly superior to flatworms' eyespots.
Point being its not about adding, it's about adapting
I agree there are other cases where evolution removes/simplifies things. Evolution is adaptation, and that adaptation can consist of adding, changing, and/or removing.
The human brain is a highly complex set of distinctive organs. Saying there are different types of brains forming the human nervous system is literally what the biology teaches us.
I imagine the reason Newton’s laws never developed before was because of all the influential know-it-alls who took empirical data (moving objects stop! Gaseous balloons rise!) and drew the wrong conclusions from it (gases want to rise up to be with all the other gases…solids want to be at rest.)
It took Newton to do a thought experiment of a projectile moving in outer space to deduce his laws of motion.
The fact is that newtons laws aren’t really observable on earth, unless you have the imagination to see it and do the mental bookkeeping of accounting for friction as a separate force.
The lizard, small mammal, human distinction maps pretty deceptively onto Aristotle's distinctions between the souls: vegetative (plant), sensitive (animal), and rational (human). So if one is trying to pinpoint the seat of intelligence, it seems to follow that we can ignore the two lower sections of the brain in favor of the higher one. Franz Joseph Gall, the founder of phrenology, himself did that, writing off the cerebellum as relevant only for producing the sexual drive [1].
Scientific theories of self-control which were nothing more than Christian dualist arguments evolved out of Gall's work and argued that intelligence involved suppression of the lower faculties, which provided cover for eugenicist and supremacist arguments throughout the 20th century and still shows up today in popular theories about how the 'limbic system' subverts the rational capacities of individuals and is used to manipulate the masses (Elon loves this theory).
Current work funded at the intersection of artificial intelligence and neuroscience still prioritizes the neocortex as the seat of rationality, with some like Jeff Hawkins (Palm founder turned brain scientist) arguing that "intelligence is an algorithm found in the neocortex". Singularity arguments rely in part on the assumption that intelligence in humans is mostly limited by the other parts of the brain, not empowered by them, and that a form of intelligence freed of embodiment will inevitably exterminate those that are embodied by right.
The truth is, neglected sub-regions such as the "lizard" cerebellum actually contain the vast majority of neurons, have been shown to have evolved disproportionately larger within early hominins [2], and are theorized to be equally involved in abstract cognition as in bodily manipulation [3]. This is something of a paradigm shift that has only been able to take shape since the late 20th-century (through the work of Jeremy Schmahmann, Peter Strick and others[4]), even though hints of it have been present in the data since it was collected, and that's because of how compelling the triune brain model has been. Research in this direction can directly address mental illnesses such as schizophrenia, but it has to be funded first [5].
[1] https://www.frontiersin.org/articles/10.3389/fnana.2019.0004...
[2] https://pubmed.ncbi.nlm.nih.gov/25283776/
[3] https://www.sciencedirect.com/science/article/abs/pii/S03043...
[4] https://www.sciencedirect.com/science/article/pii/S089662731...
[5] https://www.youtube.com/watch?v=5UUqKuhvTk0
In general I think this effect contributes to a lot of "over-debunking". We see way over-simplified, yet very loosely accurate, mid 20th century scientific models like the triune brain, "ontogeny recapitulates phylogeny", the left-brain vs. right-brain, and the idea that differences in language contribute to differences in cognition; and then silly people take these models way too far and use them to justify dubious things; and then they become over-debunked to the point that speaking them aloud immediately ostracizes you as some outdated bigot; while the whole time the models themselves have been reasonably OK high-level starting points for discussion that obviously need revision for any lower-level details.
> The truth is, neglected sub-regions such as the "lizard" cerebellum actually contain the vast majority of neurons, have been shown to have evolved disproportionately larger within early hominins [2], and are theorized to be equally involved in abstract cognition as in bodily manipulation.
The relative number of neurons is not evidence for or against the model, nor the fact that they were larger in early hominins. Showing their involvement in abstract cognition is more interesting, but that's only evidence against the triune brain if you make the exact same mistake that you're criticizing, which is assuming that "abstract cognition" is some high-level uniquely human (or primate) trait. If that exact "abstract cognition" also exists in reptiles and birds (and it appears to), then the fact that the cerebellum contributes to that cognition is not evidence against Triune Brain.
I think its important for people to also spread the idea that "this is known to not be correct". Bad mental models continue to proliferate for generations (bad here not being a value judgement but rather of their known incorrectness and lack of predictive power).
It's like when you tell people that the alpha/beta dynamic amongst wolves came from one flawed study that has not been replicated and shown to be false many many years ago now. Same with "learning styles" research. Its difficult to approach the subject in a way that doesn't cause people to get defensive sometimes - they like the simplistic model which may once have been a fine point for a beginner but they got stuck in it and it can impair their growth and understanding.
It's fine for a layperson to walk around believing whatever they like - its likely closer to the truth than whatever they might otherwise have thought, or at least got them thinking. It becomes a problem when people actually base decisions off these things.
Is the simple metaphor of 3 layers in the brain equivalent to saying gasses want to be together and solids want to rest?
I think part of the debate in the comment section is on what kind of order / pattern we are trying to capture with the analogy. Does it make more sense to be analogous to the structural observations, or a more functional equivalency?
You could say an ocean is like a desert in that they are vast and empty with respect to surface structures observed by a human traveller, but obviously from a functional /environmental perspective the two almost couldn't be more dissimilar
Based on the rather casual way the author is using language in this piece, I'd bet that the researchers forgot that what they are describing are (nested) model(s) of reality...or that that level of precision is "pedantic" (the consequence being the confusion in this comment section).
And do living reptiles, today, not also "have a basal ganglia which evolved from reptiles?" seems we've a name collision, here. Perhaps we should refer to our ancestors as "proto-reptiles," or else our contemporaneous cousins as "post-reptiles" whose brains have had just as many years' time to depart from our common reptilique ancestor.
My understanding of that is that all reptiles have a basal ganglia, because it was inherited from the common ancestor of reptiles.
And non-reptiles don't have a basal ganglia because their ancestors didn't have one.
Mammals and reptiles share a common ancestor with an ancient amniote, not a reptile
> Synapsids[a] are one of the two major clades of vertebrate animals that evolved from basal amniotes, the other being the sauropsids, which include reptiles (turtles, crocodilians and lepidosaurs) and birds.
> the only extant group that survived into the Cenozoic are the mammals.
> The animals (basal amniotes) from which non-mammalian synapsids evolved were traditionally called "reptiles".
> It is now known that all extant animals traditionally called "reptiles" are more closely related to each other than to synapsids, so the word "reptile" has been re-defined to mean only members of Sauropsida (bird-line Amniota) or even just an under-clade thereof
Yes. Anything this simple will be wrong. Almost everything you learn in school before graduate level courses will be wrong. Most of it won't matter to you unless you start working in that field.
[1]https://en.wikipedia.org/wiki/Reality_Is_Not_What_It_Seems
From what I understand, in many fields its pretty clear that most of the stuff in graduate courses is, too, its just that then next step toward right is less clear and more disputed than for the earlier wrong stuff.
If the triune brain model was completely false (as stated by the caricature of "brain is not an onion with a tiny reptile"), it would not be straightforward to even identify the neocortex -- how do you know it is 'neo', what is it a 'neo' of and so on?
So the fact that we can meaningfully talk about these areas of the brain suggests that there is in fact continuity and building-upon happening in our evolutionary journey, although of course it's not like the cartoon they show (which I have never seen before from anyone seriously talking about this topic, I might add).
This is a sort of proof-by-etymology and it isn't very persuasive. We have all kinds of words that derive from misunderstandings that have stuck, even long after the original misunderstanding was resolved. The geographical equivalent of this would be to say "we call them Indians, so they must have originated from India at some point!"
It's entirely possible that as our understanding of the brain evolves, this layered-over-time model will be seen as a quaint misunderstanding, but we'll still use the original names for the sub-organs because there's too much inertia to change them.
I don't think that the intention of the article is to say it's completely false. It's that there is no neat evolutionary separation between the different parts of the brain. The "reptile" brain in humans is not truly the brain of a tiny reptile. We inherited a similar structure, but it evolved with us just like the rest of our brain.
The same goes for the tiny reptiles we see today, their brains also evolved alongside them. If we truly had a tiny reptile inside our brain then logically we could simply study the behavior of tiny reptiles if we wanted to study that part of the human brain. Which is probably the kind of misconception the authors of the article want to refute.
I took this as the key point addressed in the introduction—this model of evolution is widely understood to be wrong. We did not evolve from reptiles, we evolved alongside reptiles from a common ancestor. Modern reptile brains have also changed in form and function since our common ancestor, and we don't have whole divisions of the brain that exist in humans but not in reptiles.
Essentially, the triune brain theory goes right alongside that classic image of the monkey evolving into a man. It's not actually how evolution works, but it's a catchy simplification that's hard to get rid of.
From the caption to the first diagram:
> The evolutionary tree (c) illustrates the correct view that animals do not linearly increase in complexity but evolve from common ancestors. The corresponding view of brain evolution (d) illustrates that all vertebrates possess the same basic brain regions, here divided into the forebrain, midbrain, and hindbrain. Coloring is arbitrary but illustrates that the same brain regions evolve in form; large divisions have not been added over the course of vertibrate evolution.
https://archive.org/details/temporallobelimb0000gloo/mode/2u...
Your "isn't it true" paragraph is all incorrect (unless it is considered in a uselessly general way). For instance, Gloor notes that all mammals have an isocortex (that seems to have started in olfactory cortex). The "reptiles" that humans evolved from is just a catch all terminology for a diverse group of life and not closely related to current reptiles. He starts the chapter noting that ancestral brains are not available for direct study.
> The triune brain hypothesis doesn't seem "wrong", it just seems like a simple categorization that is useful for making big-picture distinctions.
Right, but having worked in the field, I can assure you that there are, in fact, too many practicing psychologists, cognitive scientists, and even neuroscientists who believe the triune model of the brain to be literally and, sometimes, absolutely true. These are the types of people whom the linked paper is trying to reach.
Misunderstandings based on these oversimplified models are driving the current debate around modular versus distributed computation in the brain[1]. Obviously, a more accurate model of the brain would account for both ideas, but there is growing concern in the neuroscientific community over the amount of grant money going toward defending older, dead-end modular models instead of improving newer, more promising distributed models, mostly as a result of entrenched interests prioritizing the maintenance of prestige over the pursuit of truth.
In short, putting bad models on blast is good and necessary for the advancement of science. You can get a lot done with the plum pudding model[2] of the atom, but you can get far more done with the Bohr model[3] which emerged only after Rutherford, Bohr, and several other physicists published several iterative takedowns of the former, and yes, they too had to deal with entrenched interests who operated under the assumption that the plum pudding model was literally and absolutely true. It took a decade of experiments and several increasingly correct models before academic consensus shifted enough to accept the existence of subatomic particles and academic consensus began its collective investment in quantum mechanics. We're now in a similar place with neuroscience in the tension between modular computational models, which includes the triune brain model, and distributed computational models, which are showing promise in rescuing fMRI studies with their strong modular tradition from the replication crisis[4].
[1] https://www.cell.com/trends/cognitive-sciences/fulltext/S136...
[2] https://en.wikipedia.org/wiki/Plum_pudding_model
[3] https://en.wikipedia.org/wiki/Bohr_model
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5457304/
If anyone doesn't understand "All models are wrong, but some are useful" I don't know if you'll reach them with this paper.
Maybe it needs to be said. It's possible the most useful papers are those that assert obvious things in ways that refute our basic models so we can see things differently. It's also possible this is a clickbait paper that isn't saying anything new, just trying to be controversial.
(The rest of the article seems much more defensible to me: well-written without quite verging into strawman territory. But I'm no expert in the field.)
The title hints at what's coming. I mean of course no one thinks there's a "tiny reptile" inside our brains, ha ha.
For overall health it is also important to understand that body needs movement and all neural pathways are also somewhat independent and also contain "intelligence".
I am not neurobiologist so hope I am not going into mumbo-jumbo too much but I workout at the gym quite often and can observe over-training or how muscles often could still work but your neural pathways are done and you cannot hold the weight even if muscle/tendons feel quite fine on its own.
It is also quite common knowledge as I read on the internet stuff on training.
So in the end I don't feel body-mind separation is useful as much and thinking that your whole body is also ones mind is super important.
If your brain is anxious, you can consciously use breathing techniques to trick it into thinking you're calm. Box Breathing for example works pretty well. Or just taking 2-3 really deep slow breaths.
An anxious/nervous brain defaults to short shallow breaths for some reason.
I've read summaries of these studies as well, but... the adrenal cortex doesn't have any sensory-processing facilities, right? In the end it's the brain that informs the adrenal gland?
Asking if the model is wrong is asking the wrong question; the important question is whether it's useful.
Roll with it.
https://www.youtube.com/watch?v=rafVevceWgs&t=5117s&pp=ygUVZ...
Why? because ultimately we are talking about a empty field of space propagated by light, similar to holograms. Things that grow here things that stem from this world do you think they really are what they appear to be? Of course not. So what are they god damnit? perhaps its better to not answer the question and like a good old mystic leave it be and open a portal to another dimension and have this experience for one self
We don't have a great strategy yet for undoing the work of an effective science educator when they teach things science goes on to disprove.
Id - base impulses, bubble up automatically and subconsciously
Ego - the self, the "me". Where the story of identity comes from, what gets judged in court.
Superego - rules imposed from on high that restrict behavior
-----
I think "opposite impulses" can be explained as a form of self-control. Let's say I see someone I'm attracted to, but want to maintain composure and stay in a neutral stance. Left to my own devices I'll flush, and my eyes will widen, maybe I'll get clumsy. Bringing an opposite-but-aligned emotion in maintains equilibrium (anger, disgust...)
I see opposite-but-aligned impulses with my dog all the time. He knows I don't like him chasing squirrels. When he sees one, he gets activated + alert, but redirects his energy into running a few paces the other way. It's a bridge between the id (Go! Chase!) and the superego (Stay calm, don't pull!)
If you are identifying with the superego, maybe you are in a situation where you more "have to"s than "want to"s?
For example, even low level auditory perception, such as how the brain evolved to localize sound directions, evolved independently in mammals and birds: https://journals.physiology.org/doi/full/10.1152/physrev.000... (this is because their common ancestor didn't have a tympanic ear).
So the Triune brain really isn't the best model for explaining what is going on in the brain. Models such as reinforcement learning don't fully explain what is going on in the brain either, but I think explanations such as how dopamine flooding the reward system can mess with predicted rewards and contribute to addiction, etc. are more useful.
I think the neocortex for the most part lets other parts of the brain control themselves... and really only has high level access. I think emotions are one of these lower level semi autonomous subsystems... but so are things like autonomous body control, balance, each of the senses etc, etc... The neocortex is playing the "Human" video game and controlling things from a high level... but cannot directly control every aspect of these subsystems... and honestly, this is how complexity is dealt with (if the neocortex could control it all, the whats the point of the other subsystems)?
The "lizard brain" claim, as far as I understand it, was never that you have a complete copy of a "lower" brain inside your brain. Nor even that you have specific structures within your brain whose implementation was evolutionarily conserved.
Rather, what I understand the "lizard brain" claim as trying to communicate, is that you have one or more components of the architecture of your brain, where the APIs presented by those components to the rest of the brain, have been mostly conserved throughout evolution. The components themselves may have internally evolved, but the structural boundaries between those components and the rest of your brain have stayed stable in a way that allows biologists to recognize those same components in the architectures of brains in vastly different species.
To put that in concrete terms: you and a mantis shrimp both have e.g. "an amygdala." The gene code for "an amygdala" may have differentiated between the shrimp and you, but there's still a conserved part of the brain's architectural plan that says "put an amygdala here."
Now for the overwrought OOP analogy:
If you imagine HumanBrain as an OOP class, then it's an OOP class that is a subclass about 800 layers of inheritance deep; with the root of the inheritance hierarchy being some prototypical bilateral-vertebrate nerve-cord class.
In this inheritance hierarchy, each layer can introduce new "features" — components of the brain that have specific APIs; in other words, members of the class with known interface types, that other parts of the class can have their implementations — but not their own APIs — altered to work in terms of.
Under this mental [heh] model, the "lizard brain" claim isn't about the LizardBrain level of the hierarchy itself; but rather is that one or more brain features seen in the HumanBrain class, are features that were introduced in or around the LizardBrain level of the inheritance hierarchy, and whose APIs have stayed stable ever since.
(Also, if you're wondering if any real-world computer software has ever done 800-layer-deep inheritance hierarchies such that it starts to actually reflect this kind of speciated evolution: yes! The programming of https://en.wikipedia.org/wiki/LambdaMOO was exactly like that. Why? Because, unlike a regular codebase, but like evolution, LambdaMOO was a gradual accretion of private objects "owned" by amateur coders, where each dev would implement the features they cared about by finding someone else's object with that feature, and forking it [i.e. prototype-inheriting from it] to suit their own needs. There was no common codebase that anyone could refactor, so it gradually came to resemble an actual biological process.)
This statement is incorrect on its face. Worse, it would be a bad scientific statement in any paper. Last, it is at once superfluous and incomplete even if it were true. Instead, a good abstract would briefly list the points of the author's preferred theory rather than waste the reader's time by only deferring to a loosely defined general authority in support of an assertion. Which is abstract writing 101, at least in fields for which writing standards are somewhat kept. Maybe that isn't the psychology field, but it should be.
The last sentence of the abstract reads as if written by said high school junior. Science authors generally don't use the word "mistaken" to describe another theory, especially in the context of theories of brain evolution nor for anything else for which literally every theory can only be a theory. Including that preferred by the author.
Good papers don't introduce their arguments / pov halfway through, or further. Good papers don't lean on deference to authority 1/2 paper before presenting what is supposed to be their evidence or theory. Good papers almost completely exclude adjectives when describing theories, conclusions, or data, let alone negative adjectives that are doing all of the work in making their yet-unsupported point.
I especially like surveying textbooks over time, to call out the originators of misconceptions, and the lazy copy pasta cohorts who followed their lead.
The misrepresentations are particularly egregious in neurophysiology, which should be a very concrete observational science, based on dissections of many species in the context of evolution.
Perhaps Just So pop-sci evo-psych theories have their reckoning with scientific reality ahead of them.
https://www.youtube.com/watch?v=gZpsVSVRsZk
The drawing of humans is from the Pioneer Plaque which Sagan was involved with:
https://en.wikipedia.org/wiki/Pioneer_plaque
Anyway it was informative and clarified things nicely. Just wish it had a better lead.
About a third of the article was dedicated to who said it and when:
>> As Paul MacLean (1964), originator of the triune-brain theory, stated: man, it appears, has inherited essentially three brains.
>> This belief, although widely shared and stated as fact in psychology textbooks, lacks any foundation in evolutionary biology.
>> The most widely used introductory textbook in psychology states that: ... The brain’s increasing complexity arises from new brain systems built on top of the old, much as the Earth’s landscape covers the old with the new. Digging down, one discovers the fossil remnants of the past
>> we sampled 20 introductory psychology textbooks published between 2009 and 2017. Of the 14 that mention brain evolution, 86% contained at least one inaccuracy along the lines described above.
>> For example, Dijksterhuis and Bargh (2001), [...] write that: when new species develop, this is done by adding new brain parts to existing old ones
>> Examples of MacLean model of brain evolution appear in other areas, including models of personality (Epstein, 1994), attention (Mirsky & Duncan, 2002), psychopathology (Cory & Gardner, 2002), market economics (Cory, 2002), and morality (Narvaez, 2008). Nonacademic examples are too numerous to fully review.
>> Carl Sagan's (1978) Pulitzer Prize-winning book, The Dragons of Eden, and Steven Johnson's (2005) Mind Wide Open were both popular books that drew heavily on this idea
fossile remnants
The quoted text give lie to the title. Nobody said it was an onion etc. Just that it was built new structures on old, all changing, integrated more or less well.
Not being pedantic, I don't think? The title is disparaging, deconstructing the idea to the point of ridicule. It's reasonable to say "Nobody said that!"
"Pedantry" is a double edged sword.
We still use models based on this to illustrate, predict, and communicate.
These things are a model. They're useful for the bounds of the model.
The brain is in fact a plump shallot with a tiny noble heron inside.
Another dumb analogy about the brain bites the dust.
The hallmark of an incorrect model in science is that it makes incorrect predictions about the natural world (experiment). What incorrect predictions has psychology made based on the incorrect triune-brain theory?
I'm going to guess zero, not because the model works, but because psychology has made no experimentally testable predictions based on it.
Sure, if you are insular and only care about how it affects the field and other scientists.
Sometimes these incorrect models are incorrect in ways that are really attractive from a narrative standpoint. The hallmark of those models is to be used to spawn hundreds of pop science books that expound on those models in unfounded ways and push people into useless behavior, sometimes at a societal level.
Maybe scientists and psychologists aren't using the idea of a lizard brain in experiments and current theories, but I know there's at least some laypeople people that use it as a way to explain their behavior or make assumptions about other people's behavior, or to form their own ad-hoc explanations and models of behavior based on poor understanding of even what was previously reported to them. I would hazard it's actually more than some, and a lot of people do it, with this or some other poorly reported incorrect model of behavior or how the body works or how the world works.
Incorrect knowledge should be corrected. Leaving it it as it is leads to myriad problems, small and large, eventually.
The "chemical imbalance" narrative with depression is also probably wrong: https://theconversation.com/depression-is-probably-not-cause...
Is it really so surprising that these simplistic narratives don't actually accurately describe how the brain works? We should be prepared to admit that the brain is complicated and we don't really know it's functioning at a fundamental level.
Ultimately, psychology was created as a pragmatic branch of philosophy with the understanding that we would not know how the brain works for quite some time but that we could still do something of value and help people.
If all of "science" involved strict rigor to the "scientific method" we'd have none of the social sciences like anthropology or evolutionary psychology.
This paper is simply pointing out differences in view points.
I think the general idea in psychology is real though, the paper gets into details which is a bit pedantic. In fact the paper literally states that they are all in agreement that all brains evolved from a common ancestor. This would be the "reptile" and for sure common features in our brain such as serotonin stem from this "reptile" brain.
Psychology gets a lot of bad rep for the reproduction crisis, but evolution should largely be worse because we can't experimentally verify anything without time travel.
So it's not like this paper is about true science defeating pseudo science. It's all really speculative.
edit: I was trying to jokingly reply "Yes {smiling-imp-emoji}" when I realized I've never seen an emoji on Hacker News before - looks like they get automatically removed!
For example the entire field of astronomy is basically unverifiable bullshit. It's all speculation. We make guesses on what's going on with the stars outside of our solar system from twinkling light that comes from light years away.
Any science to verify the claims made by astronomy with the amount of rigor you demand would involve light speed space ships to go to those stars and verify.
If we could do this I think you'd find a ton of astronomy would be flat out wrong.
Nonetheless the field is still useful and legitimate despite the high likelihood a lot of it is wrong and despite the fact we can't verify much.
When it comes to research publications in general, I very much prefer to hear an objective, good faith presentation of the major viewpoints, with the author taking an opinionated but measured take in the conclusion as they review the overall weight of the literature. I'm sure there are issues with this "triune brain" model, but at a certain level every model is inaccurate; the real question is whether a model is useful in its framework, and the answer has a degree of subjectivity such that I do not think it is fair to categorically reject the perspectives of opposing experts in the field.
It's an interesting idea. I'm not sure why the parent is being downvoted.
https://www.amazon.com/Notes-Complexity-Scientific-Connectio...
Probably because he stated it as a fact instead of an interesting fringe theory.
Or do you have other ideas how to do proper testing?
Because otherwise experiments with control groups, electrodes, MRT etc. are a thing in psychology. But you can only achieve so much with it.
Many people are working on bridging neuroscience and psychology but it hasn't happened yet.
And the reason why bridging is not really happening, because of the ethical restrictions. But this is my hypothesis. The other hypothesis might be, that too many careers depend on models that would not hold up by experiments, but I really cannot judge here because of lack of knowledge.
They might believe this in the same way that some UX people might view all of software as a subset of UX, because everything ends up as an experience for some user somewhere.
[1] https://scholar.google.com/scholar?as_ylo=2019&q=quantum+bra...
Well, for starters don't call them studies, call them "hunches" or "intuitions" or whatever you like to indicate that there is actually no real evidence to prove your thesis.
Occam's razor tells us to believe that it's much more plausible that psychologist publish massaged data to keep getting funded, than because it's actually very hard to admit that "we don't know for sure, this study proves nothing".
Have you ever heard of my fellow Italian professor Francesca Gino?
Atomic bombs are very dangerous too and not very easy to "test them right", but atomic physics is a real science.
Anyway, the problem in psychology is that psychologists often lie and fabricate false evidence, not that the rats aren't enough.
There are multiple studies about it, published by scientists, most of them agree that "Don’t trust everything you read in the psychology literature. In fact, two thirds of it should probably be distrusted."
There's a point where a field can't keep going on shielding behind the false myth that "the problem is that we can't test on humans".
Can you link a study, that makes such a claim?
Of course I can, I took it from a study!
https://www.nature.com/articles/nature.2015.18248
some other studies on the subject, not all agreeing on the conclusions, as it is naturalhttps://pubmed.ncbi.nlm.nih.gov/29861517/
https://www.sciencealert.com/two-more-classic-psychology-stu...
https://www.pnas.org/doi/10.1073/pnas.2208863120
the real problem is that the kind of psychology studies that gets the more attention on the media, that shape the culture and the beliefs of the general public and that are often used by governs and institutions (even medical ones) to deploy policies, health care plans, school or work environment guidelines, etc. etc. are those that are less trustworthy, that fail to be replicated the most and more subject to interpretations and subjective biases, in particular social psychology (citation: Social Psychology (38% success rate, n = 256).)
I think they're still doing science, it's just much more difficult given physical and ethical constraints.
* Psychology is not a "real" science because it doesn't produce quality evidence.
* But quality psychological evidence is (too) hard to produce.
See how the second point doesn't really refute the first?
That's my primary issue with this. Phrenology can also be called "not real science" but it doesn't seem fair to paint both with such a broad brush. There's more nuance involved than an off-the-cuff "not real."
Though at this point it all feels too belabored to carry on.
An interesting application of weasel words and passive voice in the article..
> providing no supporting evidence
I checked, there's seventeen separate citations for evidence in the "What's Wrong" section as well as several figures.