Fig. 3.

Absolute responding on the sucrose-associated lever by sensitized and control rats during CS+ sucrose cue presentations and baseline precue time periods throughout the extinction test session. Sensitization did not increase baseline lever pressing in the absence of the sucrose cue, because the control rats actually lever pressed slightly more than the sensitized rats during each precue time period. This pattern of responding was reversed by the presence of the cue, however, because the sucrose cue evoked considerably more lever presses from sensitized rats than from control rats during each cue presentation. Thus, the magnitude of the incentive cue effect while drug-free was always greater in sensitized rats than in control rats.