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Hormone Cycles Affect Men's Test Results, Study Finds : Biology: Psychologist says males are prey to variations, just as women are, but on a yearly basis.


When psychologist Doreen Kimura reported three years ago that women's performances on standardized tests vary with their hormonal cycles, she was roundly criticized for her "sexist" attitude.

Critics charged that her results reinforced the idea that women could not handle certain jobs because they were prey to their emotions once a month.

Now, however, Kimura has closed the loop by finding the same sorts of hormonal variations in men's performances on the tests, suggesting that they, too, are captives of hormones.

It took her a little longer to get the results for men, she reported Wednesday at the Society for Neuroscience meeting in New Orleans, because men's natural hormonal cycles are yearly rather than monthly.

The new study should further illuminate the differences in thought processes between men and women and go far toward explaining the variabilities in such differences reported by others.

Kimura's findings suggest that "there is something here worth looking at," said UCLA psychologist Melissa Hines, who is studying links between hormones and performance.

Researchers have long recognized that women perform better than men on some types of standardized tests, such as those that measure muscular coordination and verbal facility. Men score better than women on certain other types of tests, including those involving spatial reasoning, such as the ability to imagine the entire shape of a three-dimensional object when presented with only one view.

Kimura, from the University of Western Ontario in London, Canada, created a stir in 1988 when she reported that women's results on these tests varied throughout the month. She found, for example, that their scores on tests of muscular coordination and verbal facility increased by as much as 10% during the times of month when their blood levels of the female hormone estrogen were high.

Similarly, their scores on tests of spatial reasoning dropped when blood levels of the male hormone testosterone were reduced. (Women have small amounts of male hormones in their blood and men have small levels of female hormones.)

Her studies of young men had also shown a curious link between testosterone levels and spatial reasoning ability. While females with above-normal testosterone levels score higher than other females on spatial reasoning tests, males with below-normal levels of the hormone also score higher than other males.

"It thus seems that there is an optimum testosterone level that is intermediate between the levels in males and females," she said in a telephone interview. To test that theory, she studied changes in test scores related to hormone levels in men.

Previous research has shown that men have a yearly hormone cycle. Testosterone levels are, ironically, lowest in the spring "when young mens' fancies turn to thoughts of love," Kimura said, and highest in the fall.

Kimura and her colleagues administered three different groups of tests to 36 males and 36 females in March, and the same tests to another group in October. The tests included those on which women normally do better, those on which men normally do better and a third group of gender-neutral tests on which men and women generally get the same scores. Such gender-neutral tests involve inferences and verbal logic.

She found that the women performed at the same level on all tests in the spring and the fall and that the men performed at the same level on the gender-neutral tests. But the men performed as much as 25% worse on the tests of spatial reasoning in the fall, when their testosterone levels were highest, and somewhat better on the tests of verbal facility.

The fact that the male scores on the gender-neutral tests did not change throughout the year indicate that the observed changes "were not related to mood changes or to some generalized effect of the seasons," she said.

UCLA's Hines noted that several other steps must be taken to confirm Kimura's results. Ideally, she said, the same group of people should be tested in the spring and fall to eliminate individual variations that might not have been accounted for in matching the volunteers.

"But to really determine if hormones are the cause, we need to administer them in a controlled situation and see what kinds of changes occur," she said. Hines is studying men with abnormally low testosterone levels, testing them both before and after they receive supplemental hormones. Those results are not available yet, however.

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