Shape discrimination in tropical fish

Abstract Two experiments are reported using Egyptian mouthbreeders as subjects in which circle/square discriminations were attempted. In Experiment 1, using large stimuli in a maze type situation, no learning was shown by any of the six subjects. In Experiment II, using a conditioned operant technique of nose banging with smaller stimuli, some learning was shown by only one of the five fish. Rapid learning of other discriminations using the square or circle as negative stimuli was subsequently shown.