Evolution of animal intelligence | Machines Like Us

Mano Singham has a interesting post up on a large scale review of animal intelligence studies.  

Animal intelligence is a fascinating topic and there have been many attempts at studying it.

Many of the individual studies look at one or other specific trait that we associate with intelligence in one species and the traits studied can differ from species to species, making general conclusions hard to arrive at. Ed Yong reports on a massive multinational study that looked across many species at one aspect of intelligence (self control) as demonstrated by two specific tasks. (You can read the paper on which his article is based here.)

via Evolution of animal intelligence | Machines Like Us.

What stuck out to me is this quote from the review.

They found a few surprises. For example, the animals’ scores correlated with the absolute but not relative sizes of their brains. In other words, it didn’t matter whether the animals’ brains were big for their size, but whether they were big, full-stop.

I’ve heard or read several times that intelligence was a factor of relative, not absolute brain size.  It’s starting to look like the data isn’t backing that up.  It reminds me how careful we have to be when accepting conventional wisdom, even scientific conventional wisdom, in areas where there’s not much conclusive evidence yet.

And of course, as Singham notes at the end of his post, there are lots of caveats and controversy with almost all of these studies, most likely starting with the way intelligence gets defined.

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8 Responses to Evolution of animal intelligence | Machines Like Us

  1. BeingQuest says:

    Human Intelligence: the most clever of cognitive capacity in all the natural world for self-destructive and self-delusional decision making and goal seeking.


  2. amanimal says:

    Thanks ‘SAP’, always brings to mind corvids since learning how intelligent they are(it still amazes me). And given your recent post on alien intelligence this fairly leapt off the screen at me:

    ‘Crows could be the key to understanding alien intelligence’

    … that I found pretty interesting. I didn’t realize mammalian and avian brains were so vastly different. I also learned how to spell “leapt” – thanks!

    Liked by 1 person

    • That is interesting. Thanks!

      Crows are probably the best counter-argument to intelligence being related to absolute brain size. The fact that they evolved intelligence also demonstrates that intelligence isn’t an evolutionary fluke. (Octopuses are another good example I think.) It seems like intelligence evolving in different evolutionary lines raises its probability substantially.

      Of course, it’s still possible that the level of intelligence humans have is a fluke. A number of factors came together for us: intelligence itself, social groups, physical dexterity, access to fire, etc. The other intelligent creatures, aside from other primates, only have subsets of these qualities. Crows, dolphins, and elephants have limited dexterity. Dolphins and octopuses have no access to fire. As far as I know, octopuses aren’t social creatures.

      It might be just the luck of the draw that we were the primates to develop symbolic thought and civilization spanning social groups before any of the others.

      Liked by 1 person

      • amanimal says:

        Thanks again, I’ll have to do some reading on octopi(3 correct plural forms: octopuses, octopi, or octopodes per M-W 🙂 …

        Also, I meant to mention that Michael Graziano has some new stuff under ‘Papers and Reviews’ at:


        … a new paper, ‘Attributing awareness to oneself and to others’, Kelly et al 2014, and still In Press ‘Speculations on the evolution of awareness’ to be published in the Journal of Cognitive Neuroscience. The Abstract is available at:


        I finally ordered his ‘God Soul Mind Brain’ – still slogging my way through ‘Philosophy in the Flesh’ 🙂 it’s kind of a long-term project though.

        Liked by 1 person

        • Thanks! I’ll check it out. After Tegmark and Ehrman, I took a break and am currently finishing James S A Corey’s space opera trilogy, ‘The Expanse’. Not quite sure what I’m going to read after that. I might finally swing back to ‘Blank Slate’, maybe.

          Liked by 1 person

  3. On the one hand, I’m not all that surprised. The idea that relative brain size has much to do with it has always seemed strange to me. If my brain were somehow transplanted into the body of an elephant, would I suddenly become stupid?

    On the other hand, humans (and also certain birds such as corvids) are smarter than you would predict from our brain sizes, so it’s not hard to see why the relative brain size idea was compelling.

    Unless I’m mistaken, larger animals tend to have more cells, not larger cells, generally. Intelligence is surely related to the complexity of the neural network implemented by the brain rather than volume, so if brain cells are approximately the same size there’s no reason why relative brain size should matter all that much.

    Thinking that the orthodox view had something to it, I assumed that in most non-human brains much of the brain is given over to processing nerve signals from all those cells. I assumed that large animals had more nerve endings than humans and so needed more brain power for processing this. This would explain why they have larger brains than humans but are not more intelligent, as it could be that the higher functions are represented by relatively small parts of the brain. On this hypothesis, we would expect brain size to loosely correlate to body size simply because of the demands of dealing with all those nerves. Deviations from the norm would therefore likely be explicable with reference to extra abilities on top of the norm, for example processing complex audio signals for echolocation in bats or higher mental function in humans.

    But even so we would still expect animals with larger brains to be more intelligent on average, simply because relative to the daily caloric intake of a large animal, the cost of running a sophisticated, intelligent brain is proportionately lower. An elephant wouldn’t even notice the caloric cost of running a human brain, whereas for a human it is quite costly indeed. It stands to reason that larger animals are more likely to evolve intelligent brains.

    So I guess humans and corvids are simply outliers. Small brains can be made more sophisticated by techniques such as increasing the surface area, thereby allowing more connections per neuron. Given sufficient selective pressure (e.g. sexual selection), I guess the caloric cost of our brains have been justified.

    Liked by 1 person

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