This article is from the Fall 2003 AFRMA Rat & Mouse Tales news-magazine.

From CNN.com

BRIGHTON, England (AP) A study involving more than 100 rats in various experiments, found that baby rats who were licked by their mothers a lot turned out to be less anxious and fearful as adults and produced lower levels of stress hormones than those who were groomed less.

Scientists found that the mothers’ licking caused the baby’s brain to crank up a gene involved in soothing the body in stressful situations.