Monday, March 07, 2005

Righties are from Mars, Lefties from Venus

Over many decades, neuropsychologists have studied the correlation between handedness and various other traits. It is well-known that the brain is divided into a right and left hemisphere, and that different activities are associated with the different hemispheres. In simplistic terms, the "left brain" is the center of speech and calculation, while the "right brain" is the locus of visualization and creativity. With the neural wiring crossing as it comes down from the head, the left brain generally controls the right side of the body, and the right brain controls the left. Thus, right-handedness is associated with left-brain orientation, and left-handedness is associated with right-brain orientation. While it is not at all dispositive, there is some correlation between left-handedness and artistic skill, and between right-handedness and verbalization skill. Of course, when you get down to the science, it's much more complex than that, and even the left/right-handed dichotomy is not so clearcut. But scientific studies have correlated handedness with all sorts of skills, such as reading ability or dexterity in moving pegs, and other seemingly unrelated traits, such as whether the hair-whorl on your scalp goes clockwise or counter-clockwise. These sorts of studies are interesting and useful in understanding the complexity of genetic expression in human development. And we can indeed say that left-handed people are different from right-handed people in ways that go unexpectedly beyond handedness.

It should hardly be surprising that the same is true of gender. Similar studies have shown some differences in skills such as verbal ability or spatial visualization that are correlated to gender. However, gender is much more muddy than handedness in separating out genetic components versus environmental components, since gender has historically had a significant impact on one's upbringing in our society. (In other words, if "men are from Mars and women from Venus", it's hard to tell what is due to Martian genes versus what is due to being raised on Mars.) Studies provide different results depending on the age of subjects tested, and studies have provided different results over time. In fact, one study that compared gender differences measured across different times has indicated that the famous differences in verbal and math aptitude have been shrinking (suggesting an environmental contribution).

It's also important to note that in all of these studies, the correlation between traits such as gender or handedness with other traits or skills are statistical correlations, clearly not random, but by no means dispositive. It's like exercise and heart disease. Everyone understands that there is some correlation between exercise and heart disease, such that those who exercise have a lower incidence of heart disease. At the same time, nobody would conclude from this correlation that everyone who exercises will be free from heart disease, or that those who don't exercise will be stricken by it.

Notwithstanding the ill-advised and much berated remarks of the President of Harvard, and the much berated over-reaction to them, nobody should be alarmed to acknowledge that there are indeed differences between men and women (that go beyond the obvious differences of genitalia). On the other hand, these differences should be taken as analogous to those of handedness. We can derive useful knowledge about human development from studying these differences, but they are weak indicators of correlated traits, and would be fairly useless to apply in specific cases. In particular, it would be ridiculous to make any specific policy decisions based on these determinants. While handedness may have some correlation with artistic or mathematic ability, nobody would expect handedness to be used as a criterion in, say, college admission, such that lefties would be preferred at Juilliard but dispreferred at CalTech. While much primitive baggage has been shed over handedness (which a couple of centuries ago was thought to say a lot about a person's character), let's hope we're nearly shed of the similar baggage that weighs on gender.

1 comment:

hatta katta ! said...

can you kindly give some reference/link for the studies that compare the lefty-righty traits. I didn't know that they even affect the scalp-whorl. Cool. Very nice read.