Abstract
The partial-reinforcement effect (PRE) was demonstrated in human eyelid conditioning by 2 groups of 24 Ss each one group received 80 acquisition trials under 50% random reinforcement. The 2nd group received 100% reinforcement. Percentage CRs over 20 extinction trials was highest for the 1st group. A 3d group was shifted from 50% to 100% reinforcement after Trial 40 and then extinguished after Trial 80. Covariance adjustments of the extinction performance of this group for acquisition performance and for intertrial blink rate indicated that the PRE was sustained through the block of continuous reinforcement. A modification of the Humphreys-expectancy version of the discrimination hypothesis could predict this result.