AbstractMale Siamese fighting fish continued to approach visual stimuli associated with conspecifics in the absence of opportunities to perform threat displays or to attack. Dominant fish performed more operant responses than subordinates when such responses led to the appearance of their own mirror images, and all fish learned to delay their threat displays if these resulted in disappearance of the mirror image. In a second experiment, subjects overwhelmingly preferred to view conspecifics (to whom they frequently displayed) compared to no stimulus or members of other species (to whom they did not display). The functions of threat displays in aggressive encounters is discussed.