Throwing a ball, jotting down a shopping list, reaching for your phone—these are actions you perform without even stopping to consider what you have to do. All of these behaviours employ a very curious phenomenon scientists term “handedness.”
The majority of people claim affiliation to the ranks of the right or left-handed, but why? Scientists have found that simple divisions such as using one hand over the other are indicative of the activation of one cerebral hemisphere more than the other.
According to a recent study, humans are not the only species demonstrating preference in handedness. Animals similarly show a distinct preference for processing information with either the left or right hemisphere of the brain.
Published in Proceedings of the Royal Society B, the study investigated how the brain divides processing tasks between hemispheres depending on information type. Researchers Culum Brown and Marie Magat of Macquarie University performed several experiments to test cerebral lateralization in animals, focusing on a number of Australian bird species. In the first task, each bird selected seeds from a background of seed-shaped pebbles. This was followed by a more demanding test, where food was suspended from a string, requiring advanced manipulation on the bird’s part to receive the treat.
Birds that displayed an obvious preference for using the right or left side outperformed those that attempted to use both sides equally. Approaching a task preferentially from one side resulted in increased activity in one hemisphere, with the right side activity of the body generally activating the left side of the brain. There is no evidence that one side is better than the other, but it seems that cerebral lateralization strongly improves task performance.
According to physiology professor William Mackay at U of T, this unequal hemispheric division is not an entirely new concept. It has long been known that the hemispheres of the brain can operate independently of each other. In radical medical cases, patients occasionally have an entire hemisphere removed and are able to function using only a single hemisphere. The brain is adaptable enough to reroute the necessary pathways through whichever hemisphere is available.
Considering the malleability of the brain, as well as the oft-quoted fact that we never actually make use of our entire brain, why is lateralization so important? Clearly there is more than enough space to mirror all of the important pathways in both hemispheres. In an interview with Discovery News, Brown stated that the division “means that a given hemisphere can become increasingly specialized at processing certain types of information.” So even though both hemispheres are capable of taking over tasks in an emergency (such as a hemispherectomy), one hemisphere is much more efficient.
The brain is like a computer and hemispheric specialization is the equivalent of a dual processor. Having each processor handle all the same tasks as the other serves no purpose—information processing won’t be any faster or more accurate—but there must be some overlap for the processors to work in tandem. Cerebral lateralization allows the separate hemispheres to tackle different parts of a problem, improving both the efficiency and accuracy with which the task is performed. For example, the left hemisphere is believed to have superior temporal control and thus plays a larger role in tasks that involve detailed manipulations of the fingers, such as writing or playing a musical instrument.
“The basic distinction of hemispheres has huge ramifications for all the associated areas of the brain,” explains Mackay. Studies concerning lateralization in humans may reveal important clues about IQ, intelligence, and problem-solving ability. Perhaps one day the question “are you right or left handed?” will reveal more about you than simply which baseball glove is yours.
