Delaying reinforcement in an autoshaping task generates adjunctive and superstitious behaviors

Rats were autoshaped to touch a lever upon its insertion into an operant chamber on a 45 s random time schedule. Occurrence of a reinforced touch on each of 12 lever insertions per session and nose-pokes at the retracted lever were monitored, as was exploratory rearing activity. Delays of 2, 4 or 8 s interposed between the retraction of the lever, which occurred either after 15 s or after a touch response, and delivery of the food pellet reward, resulted in progressively slower acquisition of the extended lever touch response. However, if rats had already acquired the response under immediate reinforcement conditions, the delays subsequently introduced did not cause a decline in autoshaped touch responding. Nose-pokes at the retracted lever occurred during both intertrial and reinforcement delay intervals over the course of autoshaping. The appearance and frequency of these (adjunctive or superstitious) behaviors depended upon the reinforcement delay and behavioral history. These interval behaviors offer measurements of learning not based on arbitrary criteria; they thus provide information about effects on endpoints, or a more global approach to learning.