The role of number and spacing of CS-US pairings in conditioned suppression

In four studies, with rats as Ss. acquisition and. where appropriate, extinction trials were presented against a baseline of ongoing licking. At shock intensities of 0.1. 0.5. 1.0, or 2.0 mA, acquisition performance was a function of number of CS-US pairings: spacing of trials (one or two per day) did not affect acquisition performance. Resistance to extinction could be predicted from terminal acquisition performance and reached a maximum after three CS-US pairings.