rat (for review see Spear, 2000), rats demonstrate higher levels of social activity than younger and older animals. These high levels of social interactions are particularly characterized by play fighting in adolescence, in contrast to social investigation which predominates the more moderate amounts of social interaction seen in adults (see Vanderschuren et al., 1997 for references and review; Varlinskaya & Spear, 2002, 2008). Adolescents not only engage in more social interactions than adults, but they find these social interactions unusually rewarding (Douglas et al., 2004).
