Brain size matters when it comes to animal self-control

Chimpanzees may throw tantrums like toddlers, but their total brain size suggests they have more self-control than, say, a gerbil or fox squirrel, according to a new study of 36 species of mammals and birds ranging from orangutans to zebra finches.

Scientists at Duke University, UC Berkeley, Stanford, Yale and more than two-dozen other research institutions collaborated on this first large-scale investigation into the evolution of self-control, defined in the study as the ability to inhibit powerful but ultimately counter-productive behavior. They found that the species with the largest brain volume – not volume relative to body size – showed superior cognitive powers in a series of food-foraging experiments.

Moreover, animals with the most varied diets showed the most self-restraint, according to the study published today (April 21) in the journal of the Proceedings of the National Academy of Sciences.

“The study levels the playing field on the question of animal intelligence,” said UC Berkeley psychologist Lucia Jacobs, a co-author of this study and of its precursor, a 2012 paper in the journal, Animal Cognition.

This latest study was led by evolutionary anthropologists Evan MacLean, Brian Hare and Charles Nunn of Duke University. The findings challenge prevailing assumptions that “relative” brain size is a more accurate predictor of intelligence than “absolute” brain size. One possibility, they posited, is that “as brains get larger, the total number of neurons increases and brains tend to become more modularized, perhaps facilitating the evolution of new cognitive networks.”

While participating researchers all performed the same series of experiments, they did so on their own turf and on their own animal subjects. Data was provided on bonobos, chimpanzees, gorillas, olive baboons, stump-tailed macaques, golden snub-nosed monkeys, brown, red-bellied and aye-aye lemurs, coyotes, dogs, gray wolves, Asian elephants, domestic pigeons, orange-winged amazons, Eurasian jays, western scrub jay, zebra finches and swamp sparrows.

Food inside a tube used as bait

In one experiment, creatures large and small were tested to see if they would advance toward a clear cylinder visibly containing food – showing a lack of self-restraint – after they had been trained to access the food through a side opening in an opaque cylinder. Large-brained primates such as gorillas quickly navigated their way to the treat or “bait.” Smaller-brained animals did so with mixed results.

Jacobs and UC Berkeley doctoral student Mikel Delgado contributed the only rodent data in the study, putting some of the campus’s fox squirrels and some Mongolian gerbils in their lab through food-foraging tasks.

Mixed results on campus squirrels’ self-restraint

In the case of the fox squirrels, the red-hued, bushy-tailed critters watched as the food was placed in a side opening of an opaque cylinder. Once they demonstrated a familiarity with the location of the opening, the food was moved to a transparent cylinder and the real test began. If the squirrels lunged directly at the food inside the bottle, they had failed to inhibit their response. But if they used the side entrance, the move was deemed a success.

“About half of the squirrels and gerbils did well and inhibited the direct approach in more than seven out of 10 trials,” Delgado said. “The rest didn’t do so well.”

In a second test, three cups (A, B and C) were placed in a row on their sides so the animals could see which one contained food. It was usually cup A. The cups were then turned upside down so the “baited” cup could no longer be seen. If the squirrels touched the cup with the food three times in a row, they graduated to the next round. This time, the food was moved from cup A to cup C at the other end of the row.

“The question was, would they approach cup A, where they had originally learned the food was placed, or could they update this learned response to get the food from a new location?” Delgado said. “The squirrels and gerbils tended to go to the original place they had been trained to get food, showing a failure to inhibit what they originally learned.”

“It might be that a squirrel’s success in life is affected the same way as in people,” Jacobs said. “By its ability to slow down and think a bit before it snatches at a reward.”

The material in this press release comes from the originating research organization. Content may be edited for style and length. Have a question? Let us know.


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5 thoughts on “Brain size matters when it comes to animal self-control”

  1. I read a study about primates, where they placed 10 Chimpanzees in a room with a ladder in the middle. On top of the ladder there was a bunch of bananas. so the reaction was that the primates would climb the ladder for the reward, but for the experiments purpose they would be sprayed wet with water every time one of them tried to go for the bananas. This had an impact on them that they would rather not climb the ladder. Later in the experiment each primate would systematically be replaced with one who did not know about the water, but each time one of the new chimps wanted to climb the ladder they would be attacked by the chips afraid of water. Finally after all the chips have been replaced the new chips was to scared to climb the ladder even though the did not know about the water. This thus proves animals with more brain capacity is thus capable of doing more but is also more prone to be suppressed by a higher figure. I further do not agree that animals with higher brain capacity live longer. brain capacity is not linked to survival directly. A bacteria cell can literally live for ever if it is in the environment that best fits it, and when there is changes it can create a cist that can withstand these drastic changes. Thus size does not matter. It is all about Darwin’s theory about survival of the fittest.

    I conclude thus that size of the brain matter when it comes to behavior but does not play a key in survival.

  2. I agree with the findings that animals with larger brains are more intelligent than those with smaller brains. Larger animals needs bigger brains because they need to maintain more neural traffic to keep their larger bodies fully functional. Larger animals also normally have a longer lifespan than smaller animals and need to control more aspects of their environment and therefore have more to gain from being more intelligent. They need to be more flexible and adaptable because the environment they live in is more likely to change during their lifetime than those of smaller animals.

    A question to consider: Does the stimulation of a brain from an early age have an influence in the intelligence of that species? Longer life equals more stimulation equals more intelligence.

  3. I don’t entirely agree to this article. Although it is obvious in general that some larger animals are more intelligent in a way than smaller animals, for example elephants as well as whales are very intelligent animals, being able to remember one event and recognising a certain smell for it’s entire lifetime, but smalller animals such as squirrels, rabbits and even monkeys are also highly intelligent animals. Each and every animal’s brain is genetically formulated to ensure that that specie is enitirely capable for survival – finding food, protecting itself and reproducting. An animal’s intelligence level should be tested in it’s own environment, own unique situations it encounters and the specific tasks it has to carry through, which is actually the true reflection of the level of intelligence the animal is most likely to reach.

    So although brain size matters, there are other factors that also play a great role.

  4. Well I agree with the previous comment, further studies should be made because in the case of a lion and a cheetah, studies show that although cheetahs are smaller and weaker they prove to be smarter than lions. As well as the case of pigs and horses. Although much smaller, pigs much smarter than horses.Scientists should look more into the make up of the brain as well as the nature of the animal to add on to their studies of the brain size being a factor in determining how smart the animal could possibly be.

  5. oh well..but i would disagree and say this is not with every animal. as in the started example: chimpanzees do seem to be less orderly than fox squirrels. Could it be we are missing a detail or there is something inaccurate. Further research is needed and necessary.


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