Pain and aggression in the rat

Abstract

The hypothesis that pain produces aggression was examined by comparison of behaviors in an established rat colony (for dominant colony males and strange intruders) to those seen in “reflexive fighting” and in a tube-test involving tailshock. During reflexive fighting dominant colony rats switched abruptly from the attack pattern displayed in the colony, to show activities (boxing, freezing) typical of colony intruders in either task. Moreover, forelimb movements similar to the “strikes” seen in reflexive fighting could be obtained during footshock to rats held alone on the grid. Finally, bites to an anesthetized conspecific were potentiated by footshock or tailshock, but only when the snout could be bitten: Such snout-bites are typical of colony intruders and not of attacking colony rats. These data indicate that pain produces a pattern of behaviors different in every detail from the activities typical of a dominant colony rat attacking colony intruders: There is, however, excellent agreement between pain-elicited behaviors and the defensive activities of colony intruders, suggesting that pain produces not aggression but defense.