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Elephants and whales have brains that are much larger than those of humans. It is presumed that much of their brain is used up for their larger bodies (after all, there is a allometric scaling between brain weight and body weight in mammals).

  • Do elephants and whales really need super-large somatosensory cortices to map to their larger bodies?
  • Have we mapped out the parts of the brains of a whale or elephant to see which parts of the brain are mapped to which parts of the body?

With whales in particular, they don't even have arms or legs, so I wouldn't expect them to have large regions of the brain devoted to, say, fine-motor skills.

Yet, it is apparent (to many people) that whales and elephants don't have drastically higher intelligence than humans. So their extra brain regions have to go somewhere. Where do they go to?

I asked the same question here, though I'm not convinced by any of the answers provided.

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"Ah, but they also have a complete three dimensions to move in, unlike us humans who only have about 2.5 dimensions to move in. Also, they have a number of different "limbs": tail, multiple fins, etc." What do you mean 2.5 ? Planet Earth is not supposed to be 2 dimensional, and humans have a wider binocular vision than cetaceans wich means better 3D vision...also humans have manual dexterity, because we have hands. –  user3902 Dec 4 '13 at 0:14
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2 Answers 2

I think what is happening is a balance of evolutionary cost and resource cost.

Evolutionary cost is the amount of "effort" that natural selection spends refining a feature. Effort that could be spent refining other features, such as making it a more efficient swimmer, etc....so it is by no means free. If you can get the same capabilities with less generations of tweaking, it's all the better. Evolutionary costs are higher on animals that have longer generations and that there are fewer total animals.

Resource cost is how much energy a feature uses, as well as such costs as the high rate of childbirth deaths caused by big baby skulls squeezing through small pelvises.

Assume that everything else being equal, larger brains produce more cognitive capability. But on a large animal, there is far less selection pressure to get the maximum "I.Q points per pound of brain," since the relative resource cost of a large brain is much lower on large animals. So whale brains use largeness, rather than super-sophistication, to get the right level of cognitive capability.

Remember, whales ARE smart, because that intelligence comes cheaply due to the low cost of brain size on a large animal. They might be the equivalent to, say, an orangutan. But unlike the orangutan, they don't have the same pressure to keep the brain small, which would have much larger evolutionary costs.

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I think you need to cite your use of 'evolutionary cost'. I have never come across such a term in evolutionary biology. Evolution does not 'exert effort' to refine features. There is either a selective pressure of a feature or not, and relevant random mutations either happen or don't. In a sexual population many mutations can fixate in a population at the same time and so there is no effort to be divided up. Everything can be 'done' in parallel. –  Artem Kaznatcheev Jun 17 '12 at 15:13
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With whales in particular, they don't even have arms or legs, so I wouldn't expect them to have large regions of the brain devoted to, say, fine-motor skills.

Ah, but they also have a complete three dimensions to move in, unlike us humans who only have about 2.5 dimensions to move in. Also, they have a number of different "limbs": tail, multiple fins, etc.

Yet, it is apparent (to many people) that whales and elephants don't have drastically higher intelligence than humans. So their extra brain regions have to go somewhere. Where do they go to?

Why not? How do you accurately measure an intelligence that is structurally different from yours? You have to know how that intelligence works, and for that to happen you need to overcome the language barrier (which is still an issue with cetaceans, since many people think they're just dumb animals! Maybe some cetaceans are like primate apes. Maybe others are like primate humans!).


Here is a pdf overview of Cetacean brains. I hope this answers your question:

A few parts pulled from the article:

Cetaceans have very large brains, yes, but humans hold the top of the proportion scale: our brains are larger in comparison to our body size than most other species.

Cetacean brains are, for the most part, like other brains. That is, they are there for the processing of cognition (among other things). A large part of this processing power goes to echolocation.

Regarding similarities between primate and cetacean brains:

the expansion of the insular and cingulate cortices in cetaceans is consistent with high-level cognitive functions—such as attention, judgment, intuition, and social awareness—known to be associated with these regions in primates.

This view is further supported by the observation that the anterior insular and anterior cingulate cortex in cetacean species having the largest brains exhibit a large number of large layer V spindle neurons, similar to those originally reported to be unique to humans and great apes. These particular neurons are considered to be responsible for neural networks subserving aspects of social cognition.

Furthermore, though specifically regarding dolphins:

Laboratory studies of bottlenose dolphins have documented various dimensions of their intellectual abilities. These include an understanding of ... (declarative knowledge); an understanding of ... (procedural knowledge); an understanding of ... (social knowledge); and an understanding of ... (self knowledge). All these capabilities rest on a strong foundation of memory; investigations have demonstrated that bottlenose dolphin auditory, visual, and spatial memory are accurate and robust.

Lastly:

Field studies have documented impressive cultural learning of dialects, foraging sites, and foraging and feeding strategies in cetaceans.

So, to recap, the cetacean brain lends itself to, among inumerable other things, advanced auditory (sensory), personal (self), and interpersonal processing (social). Also, dolphins, and maybe other species as well, have advanced memory and language processing capabilities.

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A good answer, but I am not entirely happy with one detail: about 2.5 dimensions. I get what you mean, but I want to point that a fractal dimension is a mathematical concept. And for example it is $d=2.5$ for the 3D quadratic Koch surface (type 2) and I guess it its not what you mean. As it may have sense (you can measure fractal dim of mountains or land with trees), I think it is good to reword it in this answer. –  Piotr Migdal Feb 25 '12 at 1:29
    
Aha, not what I meant actually. :) I was making a bad joke about humans' limited ability to move in the up/down dimension, as compared to cephalids which have nearly unlimited motion, at least underwater... –  BenCole Feb 27 '12 at 14:34
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