Does a Small Brain Make You Dumb?

You missed the point. No one claimed “simply size.”

You didn’t read it at all. It’s about the relative size of particular brain regions. That’s what I wrote in my post. You’re not reading.

Since you don’t even read before writing, the only word in this sentence worth a second glance is “problematic,” and it refers to the tendency of uninformed commenters on this forum to cast aspersions on science that they haven’t even tried to understand. There is no more problematic stain on this forum than that one.

Pot… behold kettle…?

“The ability to learn from others, invent new behaviors, and use tools may have played pivotal roles in primate brain evolution.”

“The reported incidence of tool use correlated with executive brain ratio, supportive of “technical intelligence” hypotheses, which argue that technology or technical skills drove brain evolution

“Our analysis reinforces the findings of other recent studies reporting that ecological hypotheses for brain evolution have been prematurely rejected, that social and ecological intelligence hypotheses should not necessarily be regarded as alternatives, and that multiple sources of selection favored the evolution of a large primate executive brain.”

They are not simply reporting correlation, but using it to argue causation.

Then using the language that way, there is an “empirical link” between using microwave ovens and low infant mortality. Is that really how we use the terminology?

Typically when someone claims an “empirical link” they mean to imply some kind of causal relationship. But I grant that the language itself need not, understood strictly literally. However, the way used in this article certainly seems to imply more than mere correlation.

The very quotes you pasted in your post invalidate your accusation. The whole article is about correlations and what they might mean. It never once asserts causation, and instead is exploring whether and how brain size is related to two particular (though broad) aspects of cognition: social intelligence and innovation. You have misrepresented the authors so thoroughly that you have removed yourself from scholarly/intellectual conversation.

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Lay some knowledge on us! Thanks for the tip on Jerison.

You keep pointing to the exceptions rather than the rule. We’re talking about species-level distinctions, but you keep talking about individual humans with small brains compared to other species.

How many times do I have to say BOTH.

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Um… Touché!

Well, I clearly have nothing further to contribute here, then.

However, I will humbly point out that when someone uses such cautious and qualified language as “certainly seems to imply…”

Then to make the absolute accusation that…,

This seems, what’s the word… “uncharitable”?

This line of thinking/research is, IMO, going to be most profitable in understanding cognition and evolution: finding a measure (and any appropriate proxies that can be used in the fossil record) of relevant network components. It might be a measure of relative size of brain regions involved in association (this is a nice review article making that point) and/or a measure of the networks’ properties at the cellular level (see paper below). The cellular approach is great but really can’t be applied to the fossil record, although can perhaps be proxied and partially inferred from genetic/genomic data.

You can say it as many times as you’d like, but that will not bring about any agreement from me. It isn’t that I am not understanding your position, I simply do not accept it.

I’ll wrap up here, since as Stephen observed I have nothing scholarly or intellectual to contribute. I am simply explaining the cause of my skepticism, but will wrap up with this…

Yes I am comparing particular exceptions that disprove the rule.

Jyoti weighs 11 pounds; as such her brain is clearly some small fraction the weight and volume of my own.

Now, if our brains, or certain components thereof, actually required a certain raw size or volume in order to accomplish our human intelligence, then diminunitive people with significantly smaller brains would lack normal human intelligence. That is clearly not the case; Jyoti is at least as intelligent as I am. What is clearly (empirically?) the case is that her (perhaps?) ~8 oz brain is just as intellectually capable as my ~3 pound brain.

I conclude therefore, and find it indisputable, that the intelligence inside diminutive brains is thus entirely the result of architecture, design, networking, and wiring inside said brain. It clearly has nothing to do with raw “size” of the brain, either in its entirety, or of any specific component therein. The size difference between my brain and Jyoti’s has 0% effect on our relative intellectual ability.

As such, the hypothesis that HCLCA brains required “increase in size” as part of their evolution in order to accomplish human intelligence is simply untenable. HCLCA could, given the right mutational pathways, have conceivably evolved into a race of humans who shared Jyoti’s physical size, brain capacity, and intellectual capacity.

Hence, I don’t care how many scientific articles I read that claim an “empirical link between behavioral innovation, social learning capacities, and brain size in mammals.” When they are making claims that intelligence is somehow related to “absolute ‘executive’ brain volumes”… and I see someone just as intelligent as I am with an absolute executive brain volume perhaps somewhere around 1/10 the size of mine…

I simply reject the idea that raw size/weight/volume, of the brain as a whole or any subunit thereof, is related to intelligence.

One last thought. When the authors wrote…

The correlations between absolute executive brain volume and all three measures of behavioral flexibility support the hypothesized relationship between absolute brain size and learning capacities…

Perhaps a pedantic criticism on my part, but “absolute brain size” seems particularly odd phraseology for speaking about “relative size of particular brain regions.”

But you’re right… probably a result of my failure to read.

You were responding to my post, which cited a specific example of studying relative size of particular brain regions. Now you seem to be referring to the old PNAS paper that @Jay313 first cited to you. That’s the one you have repeatedly mischaracterized as making claims they did not make. That paper discusses both absolute brain size and some other metrics.

Besides disparaging evolutionary science, which you do not understand and have not tried to read about, you claim to “disagree” with the argument that absolute brain size plays a role in cognitive capacity, and you do this by citing individual cases. You reveal deep misunderstanding of basic scientific reasoning, of differences between words like ‘empirical’ and ‘causative’ (which you could understand by using a dictionary), and of conceptual discussions about relationships and trends (such as between brain size/structure and cognitive capacity) that are not refuted by shallow observations of single cases. If you want to actually discuss science, you would need to read with integrity, with some meager attempt to actually understand.

Well, sorry for any confusion, that was the only article I was ever referring to, I don’t have time to read everything possible, but that article was of interest to me.

Yes, the paper that, as you described, discussed “absolute brain size” was the one I was referencing.

So, yes, guilty as charged. I probably mischaracterized it as having discussed “absolute brain size.”

Again, guilty as charged. I do disagree with the idea that absolute brain size plays a role in cognitive capacity. Citing individual cases, like that of Jyoti Amge, is what I like to refer to as “counter-evidence.”

So, yes, I say, and maintain, that the magnitudinous difference in her and my absolute brain size does not play a role in cognitive capacity.

Do you disagree?

You are mistaken about basic empirical reasoning. A single case, even if it showed what you claim, would not and could not falsify an overall fact of covariance. Your error is about basic reasoning. There is nothing to “disagree” about. The evidence shows covariance of brain size and cognitive capacity. A single outlier would only be relevant if the claim was that differences in brain size always and must indicate differences in cognitive capacity. That’s not even close to the claim under discussion. And we’re not even addressing whether your case actually goes against the trend. And we’re not even discussing whether your case would in fact show that brain size was affecting cognitive capacity, in that very case, all things considered. There are so many errors in your reasoning.

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But it’s not counter-evidence. It’s a non sequitur. You are comparing humans with varying brain sizes and saying, “No relationship to intelligence!” The paper that you’re criticizing is comparing one species to another (humans to apes to monkeys) in terms of the typical (or average) brain size for each species. They are comparing averages for each species, and you are trying to compare extremes within a species (ours). I think this is called the fallacy of apples aurantia placent ei, or as we say, apples to oranges.

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So, actual brain size has no bearing on intelligence… only average brain size…?

Point is twofold, and I’ll try to show the connection with other species. Again, I think this should be self-evident, so if you don’t concur we’ll just have to close up here. But my points are…

  1. if human intelligence can exist in a brain of 3 pounds, and the same human intelligence can just as easily exist in a brain of 1/2 pound, then the difference between them is arrangement and architecture… not size.


  1. if human intelligence can exist in a brain of 3 pounds, and the same human intelligence can just as easily exist in a brain of 1/2 pound, then it was not necessary for a human-chimp-ancestor to evolve a larger brain to achieve human intelligence, when the same intellectual capacity could have been achieved while evolving a smaller brain.

So, in a nod to the original post…

“Does a Small Brain Make You Dumb?”


I’ll take the part in bold as your hypothesis and show you why your conclusion isn’t true.
Briefly, brains are metabolically “expensive.” For example, the human brain represents 2% of body mass but burns 20% of available calories. Because brains are expensive tissue, primates are particularly susceptible to extinction. (In case you ever wondered why we are the only Homo still around.)

Now, we’re in a position to answer your question: Could human intelligence have been achieved while evolving a smaller brain? Larger brains not only required more calories to sustain, they required longer periods of gestation and maturation. The adaptive response to these pressures was sexual division of labor and, more importantly, greater social cooperation in the feeding and care of infants, which resulted in earlier weaning, shorter birth intervals, and higher overall fertility rates compared to other great apes.

This move toward cooperation rather than competition is the backbone of human society, and it was necessitated by the calorie requirements of a larger brain. Without the selective pressure to keep up with the growing brain’s constant demand for more and more calories, humans would not have learned to cooperate and share resources to survive. Interestingly, two other things that we consider uniquely human also rest upon cooperation – language and morality.

So, without larger brains and their corresponding energy requirements, humans would not have invented alloparenting and learned to cooperate, which is the basis for human language and morality. The answer to your question is therefore:

Human intelligence could not have been achieved while evolving a smaller brain.

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I don’t even know how to respond to this myself, I’d be interested if you can find anywhere this idea is well documented. But it requires me to believe that, if not for larger brains, even ever-growing in intelligence, early humans would never have figured out how to cooperate. The caloric requirements of larger brains was a single point of failure, no matter how intelligent they grew in other respects, no matter how beneficial communication may have been in other regards, no matter how many experiences of food scarcity, no matter how scarce the environment they were located, no matter how many other environmental or societal factors were at play… without the extra caloric requirements necessitated by a larger brain humans could never have learned cooperation, and cooperation is the sine quality non of intelligence. I pray you forgive me for remaining incredulous.

Is it possible that both sides of this discussion are correct? A larger brain was the initial requirement. With the increase in brain size it was possible for a re-architecture to take place. With this new architecture in place a smaller brain would exhibit the same level of intelligence.

Example for @Daniel_Fisher

A software program, due to customer demands for more bells and whistles, continues to grow in size, complexity, and computational requirements. To keep up the hardware has to continually be upgraded, bigger, faster, higher power consumption. At some point management says this has to stop so the developers are tasked with changing the software to use less powerful hardware. There are successful (surprise, surprise) in this. Now the software can run with the same functionality in less powerful hardware. From the outside it appears the bigger hardware was required to reach the levels of functionality needed.

I think something of this sort happened to H sapiens about 70 k years ago with the appearance of behaviorally modern humans. I think this is when God reached down and made man into a form that could know Him. Since it was so recent there hasn’t been time for natural selection to begin to work toward smaller brain sizes, but give us a few 100,000 years and we may all be wearing size 4 hats.

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I think there is some evidence for this; modern human brains are shrinking somewhat. That could just mean that astrocytes are getting smaller :nerd_face: but it’s a good reason to keep in mind that the size-to-function correlation is only of broad significance.

Unfortunately for “both sides,” Daniel cannot or will not engage with the data that shows him to be wrong, and has explained why: he wants to somehow undercut natural evolutionary explanations for human intelligence.

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“Because brains are expensive tissue, primates are particularly susceptible to extinction.”
“Larger brains not only required more calories to sustain, they required longer periods of gestation and maturation.”

“The adaptive response to these pressures was sexual division of labor and, more importantly, greater social cooperation in the feeding and care of infants, which resulted in earlier weaning, shorter birth intervals, and higher overall fertility rates compared to other great apes.” Cooperative Breeding and Human Cognitive Evolution

Is that good enough for a start?

Very enjoyable, yes.

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