Figure 1.

Effect of social isolation duration on responding for social play behavior. After 24 h of social isolation, rats obtained more rewards (a) and reached a higher breakpoint (ie, the largest number of lever presses made for a single reward) (b) than after 2 h of social isolation. Frequency of pinning was higher after 24 h of isolation (c), whereas social exploration did not differ as a result of isolation (d). n=14; all rats were tested after both 2 and 24 h of social isolation. Data are presented as mean+SEM. **p<0.01, ***p<0.001.