Key stimuli and the recognition of the physical environment by the paradise fishMacropodus opercularis

Recognition of features of the physical environment by the paradise fish was examined in the course of passive avoidance conditioning, in the presence of a key-stimulus-carrier dummy. During conditioning, the fish were placed into one of two differently arranged shuttle-tanks according to a random schedule. If a fish entered the dark compartment of one of the tanks it was punished by shock or, for some groups, confronted by a predator-like dummy; the other tank was safe and without the dummy. It was found that in the presence of the key stimulus carrier, associative learning was concentrated on the stimulus carrier, and that the less salient features of the physical environment were not associated with the punishment.