Fig. 2.

Individual-subject data from experiments 1 and 2 and subgroup data from experiment 2. a Individual rats’ choice of the nicotine lever as a percentage of all responses within the session, averaged across all concurrent access sessions. b Acquisition and extinction training from experiment 2, presented separately for subgroups of rats with a preference for nicotine that was above 50 % (Nic-Pref.) or below 50 % (Suc-Pref.) in (a); (b) corresponds to Fig. 1c, where all rats’ data were averaged. c and d Response rates from concurrent access testing in experiment 2 presented separately for the two subgroups; these panels correspond to Fig. 1d, where all rats’ data were averaged. All points except those in (a) represent mean (±sem)