Mean (±SEM) time-sampled observations of (a) contacts with the adjoining wall, (b) rears above the active lever, (c) forepaw entries into each quadrant (Q1-Q4) of the chamber (Q1 and Q2 boarder the adjoining wall), and (d) rears observed in each quadrant in male rats during the first nicotine self-administration session in Experiment 1. Rats were either isolated (white bars) or given limited social contact through a mesh barrier (Social, black bars) during the session. See Table 1 for n/condition. Asterisk (*) represents an increase compared to the Isolated group, independent samples t-test, p <0.001. Plus sign (+) represents lower incidences in Q3/Q4 compared to Q1/Q2, Wilcoxon signed ranks tests, p <0.05.