This article is from the WSSF 2013 AFRMA Rat & Mouse Tales news-magazine.
From the book Animal Wise, chapter 5,
The Laughter of Rats
Did You Know? Mature female rats seem to prefer play-experienced males when given the choice on a mate. He has developed proper social behavior, knows how to approach other rats, how to read another rat’s intentions, and knows how to make friends.