An objective technique for recording shock-induced aggression in unrestrained pairs of rats

Pairs of rats received grid shock in a conical enclosure. Each shock elicited the stereotyped fighting posture. An omnidirectional pole, which was always between the rats, was accidentally operated whenever the rats fought. The number of pole hits, and the number of observed fight bouts, increased with current intensity. The number of pole hits served as a reliable and objective measure of shock-induced fighting in rats.