Mean BrAC and cWFA over experimental time.
 Time −25 until 0 min = priming interval with experimenter-prompted work. Voluntary work for rewards started at time zero. Time 0–75 min = ascending phase; time 75–150 min = plateau phase.We, therefore, explored whether naltrexone treatment would affect VWR differently during the first and the second half of the experiment. We based these analyses on a predefined per-protocol sample, excluding three subjects of the naltrexone group: one who did not complete both sessions and two naltrexone group subjects in whom the second-session naltrexone blood levels were zero. Due to this hypothesis-generating approach, no adjustment was applied for multiple testing.During the initial ascending phase (start to 75 min of VWR), cumulative work for alcohol decreased in the naltrexone and slightly increased in the placebo group (mean difference in cWFA: −32 ± 67.2 vs. + 6 ± 53.1, t(41 )= 2.093, 