(NaturalNews) Animals with larger brains have more self control, according to a landmark study published in the Proceedings of the National Academy of Sciences on April 21.

The study is the first large-scale investigation into the evolutionary basis of self control, the researchers said.

"We talk a lot about how we physically evolve, but what our brains actually do, across species, has not been examined in this level of detail," said researcher Mikel Delgado of the University of California-Berkeley.

The study was especially significant for its ambitious scope. It involved 58 co-authors at 25 separate institutions around the world, and 567 animals from 36 species. The animals studied included apes (bonobos, chimpanzees, gorillas and orangutans), old world monkeys (Hamadryas baboons, olive baboons, long-tailed macaques, rhesus macaques, stump-tailed macaques and golden snub-nosed monkeys), new world monkeys (capuchin monkeys, marmosets, golden-headed lion tamarins, spider monkeys and squirrel monkeys), lemurs (aye-ayes, black lemurs, brown lemurs, mongoose lemurs, red-bellied lemurs, ring-tailed lemurs, ruffed lemurs and Coquerel's sifakas), rodents (Mongolian gerbils and fox squirrels), elephants (Asian elephants), canines (coyotes, dogs and gray wolves) and birds (orange-winged amazons, zebra finches, Eurasian jays, western scrub jays, domestic pigeons, song sparrows and swamp sparrows).

"No one would be able to do this on their own; no lab would be able to study this many species," Delgado said.

Measuring self-control

The researchers chose to study self-control because it is an aspect of cognitive ability that is relatively easy to measure. Self-control was defined as the ability to inhibit counterproductive behavior even in the face of a powerful incentive.

All researchers, though working on different animals at different locations, agreed to perform the same two tests using the same methodology, in order to be able to accurately compare performance across species.

In the first test, animals were first trained to access food through an opening in the side of an opaque container. The food was then moved into a transparent container of the same design. Animals were ranked higher for self-control if they moved toward the side opening immediately, and lower if they first moved toward the spot where the food was visible through the container.

Delgado and Berkeley psychologist Lucia Jacobs performed the only rodent studies.

"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."

The second trial consisted of placing three cups (A, B and C) on their sides, with food inside cup A. The cups were then placed upside down, and the animals were allowed to approach. Once they had learned to turn over cup A, they were shown the food being moved to cup C before the cups were turned over. Animals that moved directly to cup C exhibited more self-control than those that first went to cup A.

"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."

In contrast with the Berkeley team's rodents, big-brained primates tended to score much higher. Overall, more self control was seen among animals with larger brains and also among those with a more varied diet.

According to Duke University researchers Evan MacLean, Brian Hare and Charles Nunn, this might be because "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."

Sources for this article include:
http://www.healthcentral.com
http://www.hngn.com
http://www.sciencedaily.com/releases/2014/04/140422113437.htm
http://newscenter.berkeley.edu/2014/04/21/animalselfcontrol/
http://www.dailycal.org