Figure 2. Operant Lever-Press Acquisition.
a) Mean reinforcers (±SEM) per session earned by STs and GTs during acquisition of food- and cocaine-maintained lever pressing (averaged over the last 5 sessions of each type). b) Mean total (±SEM) food and cocaine reinforcers earned by STs and GTs upon meeting the response acquisition criterion for each response/reinforcement alternative. * p < 0.05.
