Werner, C., Latane, B. 1974. Interaction motivates attraction: Rats are fond of fondling. Journal of Personality and Social Psychology 29, 328-334.

In 3 separate experiments, 110 male albino Sprague-Dawley rats were given the opportunity to approach either a tethered stimulus rat or a responsive human hand. Ss were very attracted to the other rats but, when allowed to become familiar with the hand, were equally attracted to and showed similar reactions to it. Social deprivation had equivalent effects on attraction to hands as to rats. Results cannot be explained by theories that attribute rodent sociability to attraction to physical characteristics only. Behavioral not physical cues and the opportunity for interaction seem to be the source and the satisfaction of social attraction.