International Journal of Comparative Psychology

Studies with several mammalian species show that the surprising omission of an appetitive reinforcer invigorates aggressive behavior. In the present experiment, dominant and nondominant individuals within pairs of male rats were identified in pretests sessions. The dominant males were then randomly assigned to one of two groups and trained in a consummatory contrast situation. Group 32-W received exposure to 32% sucrose solution and was then shifted to water; Group W-W received exposure to water throughout the experiment. Immediately after a shift to water, nondominant males were introduced in the training box for a 5-min-long session. The previously dominant males of Group 32-W exhibited a significant decrease in aggressive attacks to nondominant pairmates, compared to the W-W dominant rats. Consummatory training in a situation involving surprising nonreward inhibits aggressive behavior. The potential connection between the present results and those obtained in experiments with inescapable shocks is discussed.