A matching law analysis of the effect of amphetamine on responding reinforced by the opportunity to run

In the present study, the effect of amphetamine on responding reinforced by the opportunity to run for a brief period of time was investigated using Hermstein's (1970) matching law equation. Eight male Wistar rats were trained to respond on levers for the opportunity to run. In each session, subjects were exposed to a series of tandem fixed ratio 1 variable-interval schedules. An opportunity to run for 30 s was the reinforcing consequence. Following 60 sessions of training, subjects were administered 0.25, 0.5, or 1.0 mg/kg of amphetamine prior to a session. Results from an analysis of the effect of amphetamine on response rates as a function of reinforcement rates on data from four rats showed that the value of Re decreased systematically as dose increased while k remained relatively unchanged. No significant drug effects were revealed from an analysis of total revolutions, local response rate, or cumulative latency to respond over the entire session for all rats. In accord with previous research, the changes in response rate functions under the influence of amphetamine were interpreted as consistent with an increase in the reinforcing efficacy of running.