Behavioral effects of pairing an S-D with a decreasing limited-hold reinforcement schedule.

Four pigeons were trained on a multiple reinforcement schedule consisting of two limited-hold schedules, one in which a discriminative stimulus (S(D)) accompanied the periodic reinforcement contingency, and one in which the discriminative stimulus was omitted. The duration of the limited-hold in each component of the multiple schedule was reduced in parallel steps. It was shown that behavioral differences between the two schedules were attenuated by this manipulation of temporal parameters. When S(D) was reduced in duration, three out of four pigeons responded with extremely high S(Delta) rates, despite the regular pairing of S(Delta) with the reinforcement contingency. These high rates qualitatively resembled the rapid rates emitted on the analogous no-S(D) component.