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Lever pressing with long IRTs (square root-transformed responses with IRTs > 0.67 s) in SHR/NCrl and WKY/NHsd, males and females, exposed to 1, 3, or 6 mg/kg PCB 153 or to corn oil only. The stippled lines represent the change in reinforcement schedule from VI 3 s to VI 180 s. Sessions 30 and 39 used in the video-analyses are marked on the x-axes in red.
