Response rate under varying frequency of non-contingent reinforcement.

Two White Carneaux hen pigeons were exposed to a 60-sec random-interval baseline procedure. Six different exteroceptive stimuli were successively correlated, within a single session, with blocks of 10 reinforcement presentations. Following this training, a non-contingent reinforcement procedure was instated with inter-reinforcement intervals of 5, 15, 30, 60, 120, and 240 sec. Within a single session, each non-contingent frequency was correlated with one of the previously presented discriminative stimuli. After an initial increase in the rate of responding as the result of a high density of non-contingent reinforcements, the rate declined as exposure to each non-contingent frequency was prolonged.