Animals, including humans, which process information using a preferred hemisphere of the brain — left or right — fare better than individuals who always use both sides of their brain simultaneously, according to a new study.
The study, published in the latest Proceedings of the Royal Society B, suggests a brain operates like a dual processor in a computer, with each of the brain's two sides kicking into action depending on the content or context of the information.
The findings also help to explain many prior surprising observations, such as why you should avoid approaching your boss, or any dominant primate, from the left-hand side.
Co-author Culum Brown explained to Discovery News that in primates, "if a subordinate approaches a dominant individual from the left-hand side, it is more likely to be aggressively attacked because aggression and fear are primarily processed by the left hemisphere."
Brown, a lecturer in Macquarie University's Department of Biological Sciences, and colleague Maria Magat add that the situation is reversed for toads, which are more likely to strike out at prey coming from the right. Fish also prefer to inspect predators using their right eye.
Brown and Magat, however, focused their research on several different types of Australian birds, such as gang-gangs, sulphur-crested cockatoos and Australian king parrots.
All of the birds participated in two tests designed to test their cerebral lateralization, meaning how strongly each bird preferentially processes information using either hemisphere of the brain.
The first task was a simple pebble-seed discrimination test, where the birds had to pick seeds out of a background of similar sized pebbles. The second task was more demanding. The researchers attached food to the end of a suspended string that the birds had to manipulate with their beaks and feet in order to get the tasty reward.
Birds with a preference for using either of their eyes or either of their legs did better than birds that used both eyes and both legs equally. This means that the most successful birds have a very strong cerebral lateralization, which "is influenced by both genes and experience," according to Brown.
He and Magat found that the pattern of lateralization, left or right bias, did not predict success as much as the strength of the particular bias did.
Carrying the findings over to humans, this suggests, in part, that a right-handed person isn't more successful than a left-handed one, and vice-versa, but people who always favor a certain hand, foot or eye for certain tasks will likely perform better than those who don't exhibit obvious preferences.
Brown says there are several reasons why such specialized division of the brain confers benefits to the individual.
"Firstly, it means that a given hemisphere can become increasingly specialized at processing certain types of information," he said. "You can ask a handyman to fix your tap, but you are better off asking a plumber to do it."
He added that assigning particular tasks to each side of the brain avoids conflict between the two hemispheres, and allows "multiple sources of information to be processed simultaneously, that is to say, animals can multitask like a dual processor in a computer."
Lesley Rogers, an emeritus professor in the School of Science and Technology at the University of New England, is an expert on brain development and animal behavior.
She told Discovery News that the new paper "confirms the hypothesis that lateralization enhances cognitive performance." Rogers pointed out that prior research showed, for example, "that parrots with a stronger right foot preference have a larger lexicon size."
Brown said problems, such as social stigma biases, have impeded studies on humans, but he hopes future research may reveal how strongly lateralized human test subjects are, which may be equated "to other measures, such as IQ or general problem-solving ability."