Avoidance conditioning of the rate of electric organ discharge in mormyrid fish

In Mormyrid fish the electric organ appears to discharge as a single unit, and the frequency of discharge is a simply quantifiable behavioural variable. Following a study showing that acceleration in discharge rate can be conditioned classically, demonstration of operant conditioning was undertaken using a yoked control procedure. For each pair of fish six to twelve series of trials were run, and in successive series the avoidance and control contingencies were reversed. The procedure permitted comparison of the contingencies successively in the same fish and simultaneously between fish. The results from eight Gnathonemus indicated that avoidance conditioning can control electric organ activity. In naive subjects avoidance conditioning produced significantly more responding than yoked classical conditioning (P > 0·02). The occurrence of avoidance conditioning was confirmed by the effects of subsequent reversals of avoidance and control schedules.