PSYCHOLOGICAL DISTANCE TO REWARD - THE AVERSIVENESS OF THE FIRST COMPONENT STIMULUS IN A CHAIN

Pigeons served in two experiments examining the aversiveness of the fi rst-component stimulus (S1) in a fixed-time (FT) chained schedule usin g a two-key escape procedure. Responding on a chain key was reinforced by a chained schedule while pecking a switch key produced brief black outs on the chain key. In Experiment 1, pigeons were first trained on a chain FT 30 s FT 30 s (i.e. overall duration 60 s) using the chain k ey alone (Phase I); then they were allowed to turn off the chain-key l ight by pecking the switch key without affecting reinforcement program med by the chained schedule (Phase II); finally, the blackout continge ncy on the switch key was discontinued (Phase III). Results showed tha t pigeons pecked the switch key only during C1 but not C2 and this beh avior was maintained only when the pecks produced blackouts of S1 (Pha se II). Hence escaping from C1 was negatively reinforcing and the phen omenon was attributed to the aversiveness of S1. Experiment 2 assessed the effect of the overall duration of the chained schedule on switch- key responses using the same procedure. With the three durations inves tigated (20 s, 40 s and 60 s), results showed that the switch-key rate was a positive function of the overall duration. Thus the aversivenes s of S1 increased as the duration lengthened. These findings are consi stent with those from choice studies in that segmentation of a schedul e extends its 'psychological distance to reward'.