For example, your new digital camera requires a sequence of three buttons to elicit the same outcome each time. That is a form of change that is predictable if you "systematically" remember sequences as rules. But "the way people move around at a cocktail party is entirely unpredictable. How long they stay and chat, who they chat with next--that sort of change cannot be systemized, as it doesn't follow laws or rules. So, mechanical change lends itself to systemizing, while agentive change does not," said Baron-Cohen.
The evidence that autism could be the genetic result of having two high systemizers as parents, said Baron-Cohen, in- cludes the fact that both the mother and father of children with autism have been found to have the following traits: They are strong in systemizing, they have increased rates of systemizing occupations among their fathers, and they show hyper-masculinized patterns of brain activity during a systemizing task.
In the third case, Baron-Cohen uses functional MRI to measure oxygenated blood flow in different regions of the brain while a person performs a specific task, such as searching for a hidden shape in a visual pattern as quickly as possible. "We found that there is a sex difference on this task, with females on average showing more activity in the visual cortex than men. On this task, a hypermasculinized pattern of brain activity would correspond to even less activity in the visual cortex than typical males show," he said.
The key quality of the mind that might drive someone to become an engineer is being a strong systemizer, said Baron-Cohen. His department at Cambridge is testing the idea that parents who are both strong systemizers are also more likely to have a child with certain talents, such as in math or music, or certain disabilities, such as language delay or autism. To that end, they are collecting data from questionnaires available to the public at www.cambridgepsychology.com/parents.
Behavioral genetics can also be used to explore the differences in personality among people, according to Linda Gottfredson, professor of Education and co-director of the Delaware-Johns Hopkins Project for the Study of Intelligence and Society. "By most estimates, the differences are due about 50 percent to the differences in our genes," she said.
Environmental influences account for the other half, but the category is subdivided into shared, nonshared and other influences, and they don't appear to have equal weight. Shared influences include family income or parenting practices in the home. Nonshared influences are differences that have an impact on a single person, such as an injury or an experience with a mentor. Gottfredson found that genetic effects are four times as influential on voca- tional choice as shared family effects.
Parental influence doesn't stand a chance next to genetics, said Thomas Bouchard, director of the Minnesota Center for Twin and Adoption Research. "That is true for virtually all psychological traits. It's one of the things that has made behavioral genetics controversial, because it's so contrary to what most people believe. So, when we say that offspring go into similar occupations as their fathers, what we're looking at to a considerable extent is a genetic effect," he said. "The discipline of engineering heavily draws on general intellectual ability, so for that, genetics is probably even more important than it is for other disciplines.
"If you were trying to predict success in engineering in terms of getting through engineering school and being successful in the occupation, the factors that would be very strongly important would be intellectual ability and interest in the engineering discipline," he said.
One genetic factor that is a major determinant in personality and vocational interest, Gottfredson said, is gender. Her re- search has shown that women are almost always interested in dealing with people, and men are more interested in dealing with things. "That's probably the most fundamental distinction in job requirements and among people in terms of their vocationally related personality traits. You can line up jobs by that," she said. Looking at a range of occupational interests with "people" on one end and "things" at the other, engineering would be at the far end of the range under "things." On the other side would be people-oriented occupations such as psychology and law.
Gottfredson said trends in the college and advanced degrees awarded to women support her "things vs. people" theory. Doctoral degrees are awarded in a spectrum of fields, from education and the social and life sciences at the "people" end to the physical sciences and engineering at the far end of the "things" side. "If you look at the proportion of PhDs who are women," she said, "it's less than half in 1980 in all those fields, and it ranges in real linear order from 45 percent in education down to 4 percent in engineering. In 2001, it goes from 65 percent in education to only 17 percent in engineering."
But if your engineering job requires you to have interpersonal skills, will you always be fighting your genes? People can be trained to interact in a poised and more seemingly relaxed manner, Gott-fredson said, but for certain people it will never "come naturally. A lot of engineers . . . will have to learn those skills" through management training.
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