Males with many sisters are less attractive to women, according to a study of rat behavior by a UT professor.

David Crews, a professor of biology and psychology, studied behavior in rats and found that female rats are less attracted to males whose families consist of a higher ratio of females.

Crews is interested in the development of personalities and said what happens in critical life stages, such as early childhood and adolescence, has a very powerful effect on how one will behave later in life.

The researchers mated the males from litters of varying sex ratios with females and found that all males were just as likely to mate, but females showed a disinterest in males with a high number of sisters and were less likely to perform a sexual soliciting ritual.

According to the study, males with many sisters seemed to mate more efficiently, spending less time mounting than rats with fewer sisters, and finish the act more quickly to compensate for their undesirable standing among females.

“These males are highly motivated to mate, but mating is a two-way street,” Crews said. “You not only have to mate, but you have to be accepted as a mate, and that is very much the case in rats just as it is in humans. Females have preferences.”

Humans are animals, and from a biological standpoint, humans are like rats, he said. They are social creatures that grow up in families.

St. Edwards University psychology sophomore Drew Sartain has two sisters.

Although Sartain generally has no problem finding a date, he said he has personality traits that differ from his friends who grew up with brothers, including being less aggressive and having more patience and sensitivity.

He said hearing his sisters’ points of view on men has influenced the way he treats women; for example, calling the day after a date.

Sartain also said that he tends to have more long-term relationships than short-term flings or one-night stands with women but understands how a girl who does not like attachment may be turned off by his attentive dating style.