marginally significantp = 0.057
Model (session x treatment) yielded that in PR, the mean number of lever presses differed across sessions ( χ 2 = 50.295, df = 6, p < 0.0001), and marginal effects indicated a significant reduction on the 4 th session (p = 0.001) and marginally significant reduction on 2 nd session (p = 0.057), as compared to the first test.