Measured differential electrodermal response as a function of (a) a .5-sec and 7-sec interstimulus interval (ISI), (b) the presence or absence of CS-UCS pairing in the initial phase of training, and (c) a reversal of stimulus relations between sessions for the group with CS-UCS pairing. Ss (N = 48) were fully informed of stimulus relations. Both ISI groups showed discrimination learning in the initial phase, and immediate discrimination reversal. Potency of verbal determiners of differential responding to electrodermal behavior and the effects of instructions on the overall response level are discussed.