Unburdened by social engineering, some females prefer males who act like males so growing up with lots of sisters makes a male less sexy - for rats, anyway.

A new study published in Psychological Science, says that the sex ratio of a male rat's family when he's growing up influences both his own sexual behavior and how female rats respond to him.
When males who were raised with a lot of sisters were presented with receptive female rats, they spent less time mounting them than did male rats that were raised in male-biased litters or in balanced families.
So there you have it.   Females may like males who are a little sensitive, like when watching "Old Yeller" or "The Dirty Dozen", but when it's time to bring the sweet lovin', they still want you to be able to bring it.