Influence of shock controllability by dominant rats on subsequent attack and defensive behaviors toward colony intruders

Thirty colonies, each consisting of a female and two male adult albino rats, remained intact for an 8-week period. Naive conspecific intruders were then introduced into each colony for a 10-min test for 5 consecutive days. Videotapes of the tests were scored for aggressive and defensive behaviors. In every colony, aggression was greatest for a single alpha male. The alpha rats were randomly given one of three treatments: wheel-turn escape training, inescapable yoked shock, or restraint without shock. The alpha rats were then returned to their colonies and an intruder test was given 26 h later. Significant decreases in aggressive responses and increases in defensive behaviors occurred in the alpha yoked group but not in the other alpha groups. The nonalpha colony partners of the alpha yoked rats showed the opposite changes following the treatment. A final intruder test 72 h later revealed that the deficits in aggression of the alpha yoked group were still present but that the behaviors of most of the other groups were beginning to return to their respective pretreatment levels. These findings were discussed in terms of the concept of learned helplessness and alternative theoretical explanations.