If it applies to rats, does it apply to humans? According to a study published in Psychological Science, male rates raised with more female litter mates are less active sexually in adulthood. The results also suggest that these males wind up being less attractive to females.

Rearranging the sex ratios of the rat litters, the researchers found that male rats reared with many sisters would behave differently as adults with females than did male rats raised in more male-biased environments, or from litters where the sex ratios were more even.

“We found that males raised in a female-biased litter exhibited less mounting than males raised in either a male-biased litter or one with an equal sex ratio, and were less attractive to sexually receptive females, eliciting fewer soliciting behaviors,” according to the study. “The reported differences in sexual behavior did not vary with the quality of maternal behavior or with sexual experience in adulthood.”

Whatever happened to the male rats growing up with lots of sisters when they were young, the experience left an imprint that the opposite sex picked up. Turns out that females tended to alter their sexual responses in very overt ways.

When they want to mate with a male, female rats wiggle their ears - “it drives males nuts,” notes David Crews, a professor of Zoology and Psychology at the University of Texas at Austin, and co-author of the report. But the females were less likely to perform this so-called “dart-hop” move with the male rats that got raised in a female-biased litter.

One possible explanation is that that males reared in a female-biased litter may be less attractive to females because they secrete less - or different - odors. It’s also possible that they may emit fewer ultrasonic vocalizations and approach responses. But it’s not just the females who get turned off. The study suggests that the male rats are so used to females that by the time they reach adulthood the allure of the opposite sex has simply worn off.

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Posted by CBSNews.com staff