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Behavioral data collected during the 12 h overnight instrumental session under a progressive ratio schedule of reinforcement presented as a function of chromosome complement (XX – open symbols; XY – closed symbols) and gonadal sex (male – left bars; female – right bars). Panel A presents the average total number of lever responses (mean +/− SEM) made during the 12 h session; Panel B presents the average ratio achieved (mean +/− SEM). *p <0.05, ** p<0.01.
