In recent years there have been an increasing number of investigations concerned with effects of early experience on behavior and development in rats and mice. The relevant literature has been reviewed by a number of investigators.1,2,4,7,15 A series of studies have been concerned with the effects of tactual stimulation in the form of handling or gentling administered either prior to or immediately following weaning of the organism. It has been shown that rats which are gentled or handled gain more weight,13,17 are less emotionally reactive to novel stimuli,6,11,17 show greater resistance to a variety of Stressor agents,9,13,16 and exhibit greater learning ability3,8 than nonhandled controls.
However, there has been a paucity of research concerned with the relationship between tactual stimulation and social behavior in rats and mice. Levine11 has shown that mice which are handled daily during infancy are more aggressive than unhandled