Thursday, August 11, 2005

NYTimes - pro-evolutionary psychology?

The NYTimes gave a one-shot column to Simon Baron-Cohen, another evolutionary psychologist.

Says Baron-Cohen:

“In my work I have summarized these differences by saying that males on average have a stronger drive to systemize, and females to empathize. Systemizing involves identifying the laws that govern how a system works. Once you know the laws, you can control the system or predict its behavior. Empathizing, on the other hand, involves recognizing what another person may be feeling or thinking, and responding to those feelings with an appropriate emotion of one's own….”

“…What of Mr. Summers's other claim, that such sex differences are innate? We know that culture plays a role in the divergence of the sexes, but so does biology. For example, on the first day of life, male and female newborns pay attention to different things. On average, at 24 hours old, more male infants will look at a mechanical mobile suspended above them, whereas more female infants will look at a human face.”

But what you'll probably NEVER read in the Times is that these claims were debunked by Elizabeth Spelke in her now-classic debate with Steven Pinker:

Over the last months, we've heard three arguments that men have greater cognitive aptitude for science. The first argument is that from birth, boys are interested in objects and mechanics, and girls are interested in people and emotions. The predisposition to figure out the mechanics of the world sets boys on a path that makes them more likely to become scientists or mathematicians. The second argument assumes, as Galileo told us, that science is conducted in the language of mathematics. On the second claim, males are intrinsically better at mathematical reasoning, including spatial reasoning. The third argument is that men show greater variability than women, and as a result there are more men at the extreme upper end of the ability distribution from which scientists and mathematicians are drawn. Let me take these claims one by one.

The first claim, as Steve said, is gaining new currency from the work of Simon Baron-Cohen. It's an old idea, presented with some new language. Baron-Cohen says that males are innately predisposed to learn about objects and mechanical relationships, and this sets them on a path to becoming what he calls "systematizers." Females, on the other hand, are innately predisposed to learn about people and their emotions, and this puts them on a path to becoming "empathizers." Since systematizing is at the heart of math and science, boys are more apt to develop the knowledge and skills that lead to math and science.

To anyone as old as I am who has been following the literature on sex differences, this may seem like a surprising claim. The classic reference on the nature and development of sex differences is a book by Eleanor Maccoby and Carol Jacklin that came out in the 1970s. They reviewed evidence for all sorts of sex differences, across large numbers of studies, but they also concluded that certain ideas about differences between the genders were myths. At the top of their list of myths was the idea that males are primarily interested in objects and females are primarily interested in people. They reviewed an enormous literature, in which babies were presented with objects and people to see if they were more interested in one than the other. They concluded that there were no sex differences in these interests.

Nevertheless, this conclusion was made in the early 70s. At that time, we didn't know much about babies' understanding of objects and people, or how their understanding grows. Since Baron-Cohen's claims concern differential predispositions to learn about different kinds of things, you could argue that the claims hadn't been tested in Maccoby and Jacklin's time. What does research now show?

Let me take you on a whirlwind tour of 30 years of research in one powerpoint slide. From birth, babies perceive objects. They know where one object ends and the next one begins. They can't see objects as well as we can, but as they grow their object perception becomes richer and more differentiated.

Babies also start with rudimentary abilities to represent that an object continues to exist when it's out of view, and they hold onto those representations longer, and over more complicated kinds of changes, as they grow. Babies make basic inferences about object motion: inferences like, the force with which an object is hit determines the speed with which it moves. These inferences undergo regular developmental changes over the infancy period.

In each of these cases, there is systematic developmental change, and there's variability. Because of this variability, we can compare the abilities of male infants to females. Do we see sex differences? The research gives a clear answer to this question: We don't.

Male and female infants are equally interested in objects. Male and female infants make the same inferences about object motion, at the same time in development. They learn the same things about object mechanics at the same time.

Across large numbers of studies, occasionally a study will favor one sex over the other. For example, girls learn that the force with which something is hit influences the distance it moves a month earlier than boys do. But these differences are small and scattered. For the most part, we see high convergence across the sexes. Common paths of learning continue through the preschool years, as kids start manipulating objects to see if they can get a rectangular block into a circular hole. If you look at the rates at which boys and girls figure these things out, you don't find any differences. We see equal developmental paths.

I think this research supports an important conclusion. In discussions of sex differences, we need to ask what's common across the two sexes. One thing that's common is infants don't divide up the labor of understanding the world, with males focusing on mechanics and females focusing on emotions. Male and female infants are both interested in objects and in people, and they learn about both. The conclusions that Maccoby and Jacklin drew in the early 1970s are well supported by research since that time.