This thesis was concerned with the effects of shock intensity on discriminative escape conditioning. At the lowest shock intensity there was a bimodal distribution of nonresponding animals at one mode and responders at the other mode. Optimum performance occurred at the lowest shock intensity at which 100% of the animals responded. At higher shock intensities performance deteriorated. An attempt to test the Yerkes-Dodson Law failed to yield conclusive results. Finally, it was found that shock intensity affected performance rather than learning. / Thesis / Doctor of Philosophy (PhD)