There is clear evidence that men perform better at spatial tasks and women outpace men on tests of verbal usage and perceptual speed, according to research conducted by Wendy Johnson, postdoctoral research fellow at the University of Minnesota, and Thomas Bouchard, director of the Minnesota Center for Twin and Adoption Research. The findings, which will be published in the journal Intelligence, indicate that there is little difference in how the genders fare as far as general intelligence, however. But since engineering positions are overwhelmingly filled by men, this further supports the theory that spatial abilities are key to success in the field.

The researchers examined three dimensions of intelligence:

• Rotation-verbal--higher spatial (mental rotation) abilities vs. higher verbal abilities;

• Focus-diffusion--problem solving by focusing on details in a linear fashion, vs. problem solving from many different perspectives at once, synergistically; and

• Memory--information retention independent of general intelligence.

Johnson and Bouchard found that there are substantial differences in how men and women approach these dimensions. Men are more likely to be geared toward the rotation and focus dimensions, while women tend to be more verbal, diffuse, and able to excel in the memory dimension. They also learned that "general intelligence [or IQ] serves as an all-purpose problem-solving ability that masks sex differences in more specialized abilities." This underscores the need to measure the individual dimensions, not just IQ, to deliver a more holistic view of a person's intelligence.

Blind spot in AP test
One specialized ability is sorely missing from the Advanced Placement (AP) tests taken by high school students in the United States, according to Philip Ackerman, professor of psychology at Georgia Institute of Technology. AP tests determine the courses students may take to put them ahead of other students when they enter college.

"If we give a battery of ability tests to high school students, we find relatively small overall differences between them. Girls tend to have slightly higher verbal ability and boys tend to have higher math ability. But, if you administer a spatial-ability test, which is not typical for SAT-type stuff, there's a big difference between males and females. That is a salient issue because spatial ability tends to be highly correlated with engineering programs," said Ackerman.

This issue has not been adequately studied because spatial ability is not included in the standard college entrance exams. However, the AP tests may show a pattern of how spatial abilities determine the course of study for some students.

"If you look at AP exams, there are big differences in success rates," said Ackerman. "As of 2004, more girls took the AP test than boys, by 155,000 tests. More boys completed the calculus tests than girls by 7,000. The clear passing rate (a score of 4 or 5) was much higher for boys than girls (43.8 percent for boys, and 35.5 percent for girls). In chemistry, boys completed 5,000 more exams and had a clear passing rate of 38 percent (vs. 26 percent for girls). In physics, boys completed almost twice as many tests as girls and had a clear passing rate of 36 percent (vs. 22 percent for girls)," he said.

The data shows that girls do measurably worse in every AP test except the foreign language exam.

AP testing has exploded in the last 10 years. From 1997 to 2003, said Ackerman, there has been a 90 percent increase in the number of AP tests taken. "It's fundamentally changed the nature of the high school experience for college-bound kids, and it probably has a lot to do with what domain they'll go into and how they'll perform in those classes," he said.