Brain size needed for human-type cognition

[njtt]

Perhaps I should add, however, that I do not really think that we should conclude, from the case studies that I linked to, that brain volume has nothing to do with intelligence or cognitive function (although they do, perhaps, suggest that the correlation may be a lot less direct than we might otherwise have expected). I do genuinely think that twickster’s evolution based arguments against the conclusion are invalid,. However, I also rather suspect that it is probable that careful, expert examination of the studies I linked to might reveal problems with them, perhaps with their methodology and/or with how they interpret their data.

Unfortunately I am not sufficiently expert in neurology or neuroimaging to say exactly what the problems (if they really do exist) might be. It is worth noting, though, that, despite the fact that it was published in the prestigious journal Science, the first report I linked to is not a peer reviewed scientific research report, it is a more-or-less journalistic, second-hand report on research that seems to have been carried out in a rather informal, unsystematic way by someone working slightly outside his normal field (he was a professor of pediatrics apparently, not neurology) and which seems never to have been formally published in a peer reviewed format.

The article at the second link has been peer reviewed, I think, and also appeared in a prestigious journal, but it is very short, less than one page long, and thus goes into very little detail.

I am not saying that both or either of these articles are completely wrong (I doubt that that is the case), but I am saying that I think it is likely that further research in this area (including, perhaps, a careful scrutiny of the methodological and logical details of the specific research in question) is likely to lead to less extreme conclusions than these two studies suggest. Brain volume may not be as closely correlated with either intelligence or cognitive function as we we might have expected, but it probably is not completely unrelated either.

ETA: TriPolar has put my final point much more clearly and succinctly than I manged to. (Sorry, I’m falling asleep here.)

[twickster]

Yeah, clearly brain size isn’t the whole story – and I could very well be talking out my ass about the evolutionary angle – but it seems to me that statistical outliers after a trait has developed don’t necessarily tell us anything about the overall development of the trait.

[TriPolar]

@twickster

Yeah, clearly brain size isn’t the whole story – and I could very well be talking out my ass about the evolutionary angle – but it seems to me that statistical outliers after a trait has developed don’t necessarily tell us anything about the overall development of the trait.

Give us some insight on the evolution of 10" tall men. Are they humans who adapted by getting smaller, or did they evolve from an earlier species that was also small?

I don’t know which dinosaur birds evolved from, but they may be quite a bit smaller than their ancestors, and more intelligent.

[GusNSpot]

Intelligence vs cognition ( is it different in a scientific way? ) vs Volume VS shape?

Possible for the actual shape to have anything to do with it? Like the early super computers? ( circled them to get faster transmissions IIRC ) Like how close a birds eye is to the part of the brain that needs that info very fast? I seem to remember reading something on that.

[TriPolar]

@GusNSpot

Intelligence vs cognition ( is it different in a scientific way? ) vs Volume VS shape?

Possible for the actual shape to have anything to do with it? Like the early super computers? ( circled them to get faster transmissions IIRC ) Like how close a birds eye is to the part of the brain that needs that info very fast? I seem to remember reading something on that.

I’m not sure how to work this angle. If it has a much smaller body it might need a much smaller part of the brain that deals with the basic functions of the nervous system, leaving more room for the bits that do the reasoning and what not.

Twix, I’m also curious about the proportions of this little guy. Usually the wee folk are depicted with oversized heads. I assume for artistic reasons there’s a need to make a larger and more recognizable face, but could the artists be making the reasonable assumption that the head will get proportionally larger as the whole person gets smaller?

[twickster]

@TriPolar

Give us some insight on the evolution of 10" tall men. Are they humans who adapted by getting smaller, or did they evolve from an earlier species that was also small?

It’s not addressed in the novel, and I’m not sure the author gave the matter any thought. This is just speculation piled on speculation.

[Colibri]

It might be mentioned that it appears that although anatomically modern humans arose almost 200,000 years ago, modern human behavior (symbolic thought, art, possibly language) may only have originated 50,000 years ago with no corresponding increase in brain size or change in superficial brain anatomy. (This is, however, controversial.) If true, this suggests that modern human behavior may have been due to a reorganization of neural networks rather than just an increase in brain size. So brain organization is a major factor in intelligence, beyond mere brain size.

[jerez]

@Colibri

So brain organization is a major factor in intelligence, beyond mere brain size.

I recall research that suggested that parts of the brain will sometimes adapt to take over the duties of another damaged part that ceases to function. If so, it might indicate that more brain matter would be an evolutionary advantage but not necessarily an essential element. However, as there’s no archaeological evidence of humans having tiny skulls, I guess it’s moot.

In any case (and even though I know nothing about this), I suspect that at present we know very little about intelligence and that, in a not-too-distant future, a better understanding of animal intelligence will change the way we define the concept.

[cmyk]

@Northern_Piper

Isaac Asimov wrote a column on this issue - one of his monthly science columns. I’m afraid I can’t remember the name of it, but he got into the molecular mechanics of the brain and essentially concluded that mini-people aren’t possible, because the brain would not be big enough.

ETA: it may have been originally published in the late 60s, because what got him thinking on the issue was the TV show, Land of the Giants.

Ironic, since he’s also the author of Fantastic Voyage.

[twickster]

@Colibri

… So brain organization is a major factor in intelligence, beyond mere brain size.

True – but wouldn’t there still be some kind of minimum size necessary before you’ve got enough neurons for such reorganization to take place?

[Colibri]

@twickster

True – but wouldn’t there still be some kind of minimum size necessary before you’ve got enough neurons for such reorganization to take place?

Probably, but we don’t know where the lower limit is. In any case, only half the volume of the human brain is made up of neurons, the rest being glia cells that mainly provide support functions.

Ants are able to engage in quite complex behavior with only about a 250,000 neurons, compared to about 7 billion in a chimp and 85 billion in a human. If there was a major selective pressure to reduce brain volume without affecting function, it’s hard to say how much it could be reduced.

Homo floresiensis, the so called “hobbit” species of Flores in Indonesia, had a brain size only about half that of its presumed ancestor, Homo erectus, and only about that of a chimpanzee. Despite this they were apparently capable of using fire and making sophisticated stone tools.

An indicator of intelligence is the size of Brodmann’s area 10, the dorsomedial prefrontal cortex, an area of the brain associated with higher cognition. LB1’s region 10 is about the same size as that of modern humans, despite the much smaller overall size of the brain.[6]

I am not sure how the humanoids in the story are supposed to be related to humans. Getting human behavior in a creature only eight inches tall would be a stretch if the brain were organized on the human pattern. But if it had evolved independently, with a radically different structure, I wouldn’t absolutely rule it out.

[John_Mace]

@Colibri

It might be mentioned that it appears that although anatomically modern humans arose almost 200,000 years ago, modern human behavior (symbolic thought, art, possibly language) may only have originated 50,000 years ago with no corresponding increase in brain size or change in superficial brain anatomy. (This is, however, controversial.) If true, this suggests that modern human behavior may have been due to a reorganization of neural networks rather than just an increase in brain size. So brain organization is a major factor in intelligence, beyond mere brain size.

Slight nitpick-- it would have to have been more than 50K years ago since it would have to predate our exit from Africa. I think you’d be hard pressed to make a case that it was less than 60K years ago, based on the fossil evidence. It also seems that we keep finding older and older evidence of symbolic art all the time. And, as you say, the whole idea is controversial to begin with.

Also, our ancestors back then might have had slightly larger brains, on average, than ours today. Of course, we have a lot more physical variation (across 7B people) than you could have hoped to find in the few humans alive then.