Vocalization as an objective measure of shock-elicited social aggression in rats

Intense vocalizations emitted by pairs of shocked rats were compared when physically separated by a transparent partition and when free to engage in social aggression. Greater vocalization occurred in the free-access condition and was positively correlated with visually observed attack scores in pairs that had prior experience with shock. A second experiment determined the influence of repeated fighting exposures upon the correlation between observed attack and vocalization. High positive correlations were obtained after initial sessions within a broad range of intermediate fighting. At high and low extremes of fighting, correlations were nonsignificant. The results are discussed with reference to restriction imposed upon variation of attack scores based upon standard criteria of observation.