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Thread: Body size and intelligence

  1. #1 Body size and intelligence 
    Forum Radioactive Isotope skeptic's Avatar
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    Indulge me.

    Just came up with a new, possibly silly, theory, that I want to bounce off some scientifically clever people. This theory is about intelligence.

    Theory : "Among mammals, great body size has the side effect of creating great intelligence."

    This theory predicts that mammals such as elephants and blue whales will be smart. OK. Not as smart as humans, but nevertheless, more intelligent than the majority of mammalian species.

    My logic is this. Intelligence confers adaptive benefit. The downside is that a big brain consumes lots of energy. Thus, it is very difficult for a small mammal to support a big brain. For such a beast, the energy demands of the brain will consume too much of the total energy economy of the body.

    However, in a large mammal, the extra energy neded to run a bigger brain is a much smaller percentage of the total energy economy of the body. So for a blue whale to add to its cerebral cortex an amount similar to the human cerebral cortex increases energy requirements by an amount that is essentially infinitesimal to that whale. Yet that small increase in brain size may increase its intelligence by a substantial amount, without the downside.

    Obviously, a large predator (like an Orca for example) has more need for high intelligence. A blue whale has less need to be smart. But if the smarts come cheap, without the energy downside, might it not happen anyway? Even for a blue whale, being smarter will be an aid to survival.


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  3. #2  
    Moderator Moderator TheBiologista's Avatar
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    New ideas go in the New Hypotheses subforum.


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  4. #3  
    Veracity Vigilante inow's Avatar
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    Interesting thought, skeptic. My initial approach is to try poking holes in it, but I do like the idea. I want to suggest an obviously big animal which is obviously not smart, but I'm too tired right now to think of any.

    Maybe I can approach this a different way... Is a crocodile smarter than a mouse or a cat or a monkey? How does your hypothesis account for something like that? Is this only within mammals? If so, would that mean that a giraffe should be smarter than a raccoon or a dog or a horse?
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  5. #4  
    Administrator KALSTER's Avatar
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    If so, would that mean that a giraffe should be smarter than a raccoon or a dog or a horse?
    ..or a Homo S.S.?

    Yeah, brain size does roughly correlate with body size, but I think of it in terms of how many body cells there are in relation to the number of neurons the animal has. With your whale analogy adding the number of neurons of a human to the mix would not make that big a difference precisely because of the body size to brain size relation.

    ..and it seems I am wrong as well:

    LINK

    "The brain of the sperm whale weighs 7,800g, the elephant's weighs 7,500g, man's weighs 1,500g, the dolphin's 840g, and the brain of a mouse weighs 0,4g. If these figures are used to determine intelligence, then the sperm whale and the elephant are five times as intelligent as man, who in turn is twice as intelligent as the dolphin, which in turn is 2,000 times as intelligent as a mouse. Should we rank animals in order of how large their brains are in relation to their body weight, then the mouse would come out on top with its brain comprising 3.2%, the dolphin's 0.9% and the sperm whale's 0,021%. Neither absolute brain weight nor the relationship between brain weight and body size provide us with sensible criteria for comparing the intelligence of different species. "
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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  6. #5  
    Forum Radioactive Isotope skeptic's Avatar
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    The problem with intelligence in animals is how to measure it. We can get a rough idea with smaller animals by how easily they respond to training. However, the largest animal that can be kept in captivity is an Orca. How to test a sperm whale? What about a blue whale?

    To iNow. I think we need to stick to mammalian comparisons simply due to the old principle of comparing apples with apples.

    I am not suggesting here that body size is going to be the biggest influence on intelligence. Just one more powerful influence. A blue whale is a filter feeder, and needs high intelligence less than that Orca. However, I am suggesting that great body size makes the evolutionary disadvantage of an energy consuming big brain much less of an effect on the evolution of that animal. Thus, even if the advantage of intelligence is not great, the larger animal is still more likely to evolve it than a smaller animal.
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  7. #6  
    Veracity Vigilante inow's Avatar
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    A worthy clarification. As I mentioned, I find it to be a fascinating idea, and I'm curious to read feedback from people better informed than myself on the topic.
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  8. #7  
    Time Lord
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    Mass or volume, neither of brain nor body, are directly meaningful. You don't find bulky old computer processors more powerful, nor do you find supertankers need more sophisticated cockpits than helicopters.

    I think what matters in brain is number of neurons. What matters in body is number of nerves. Subtract nerves from neurons to roughly find the "slack" available for thinking beyond immediate sensation and motor control. Some modes of existence inherently demand more banal brainpower. For example dragonflies must dedicate precious brain resources to flight, whereas whales have relatively streamlined motor control and only incidental need for sensory awareness.
    A pong by any other name is still a pong. -williampinn
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  9. #8  
    Forum Radioactive Isotope skeptic's Avatar
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    iNow
    Thanks for the encouraging comments.

    Pong
    Number of neurons is important, but that translates into increasing brain mass and energy use.

    In fact, with intelligence, what counts is brain mass (number of neurons) in excess of what is required to control normal body functions and sensory interpretation. Large animals will have large brains just to control that large body. However, their intelligence needs that little bit extra.
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  10. #9  
    Time Lord
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    Quote Originally Posted by skeptic
    Number of neurons is important, but that translates into increasing brain mass and energy use.
    Yeah, and brain/body mass is an indirect (though most expedient) measure of neural/nerve quanta.

    Obviously some species maintain heavier sensory loads than others. Bloodhounds have 4x the smell buds of typical dogs... unsurprisingly bloodhounds have one-track minds. Sensory load may not be a drag when plasticity is possible: You close your eyes to visualize a maze. Apparently some spiders can pre-plan maze solutions... in their case I guess they "simulate" maze runs by virtually stepping through long sequences of motor controls.

    Regarding intelligence advantage in blue whale, remember that the turkey adapted gross stupidity. In turkey's case bright ideas are a liability. The theoretic ease with which even big-brain stupidity could be adapted when effective, may be a warning to us... or an inspiration!
    A pong by any other name is still a pong. -williampinn
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  11. #10  
    Universal Mind John Galt's Avatar
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    The structure of the brain is as important as the size of the brain. Human brains and IIIRC the brains of cetaceans, have a more complex structure than your average mammal. I'mnot sure about elephants.
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  12. #11  
    Time Lord
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    I think that blood flow rates would have to matter as well. Warm blooded animals have a natural advantage over reptiles, because our blood flow is more consistent. Big animals have slow heartbeats.

    If a human wants to think really hard, we can vary the blood/oxygen flow to our brain by quite a lot to make a concerted effort at something. The rest of the time, maybe we just give it enough oxygen to keep it alive.

    Quote Originally Posted by Pong
    Quote Originally Posted by skeptic
    Number of neurons is important, but that translates into increasing brain mass and energy use.
    Yeah, and brain/body mass is an indirect (though most expedient) measure of neural/nerve quanta.

    Obviously some species maintain heavier sensory loads than others. Bloodhounds have 4x the smell buds of typical dogs... unsurprisingly bloodhounds have one-track minds. Sensory load may not be a drag when plasticity is possible: You close your eyes to visualize a maze. Apparently some spiders can pre-plan maze solutions... in their case I guess they "simulate" maze runs by virtually stepping through long sequences of motor controls.
    So you think maybe all that extra brain power goes into the whale's sonar? Same for Dolphins?

    I guess Humans are specialized because we direct our brain activity toward abstract thought, and better vision (or at least colorized vision). But our sense of smell is abysmally poor by most standards. That makes sense. We save resources where we can.
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  13. #12  
    Forum Junior JennLonhon's Avatar
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    Just one little thing.... As far as I know, intelligence doesn't depend on brain size but on the connections inside the brain, right? So, yes, I guess a bigger brain would have "more space" to make connections but that doesn't necessarily men that those connections will be made....
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