Effects of relative proximity to reinforcement of a stimulus intruded on fixed- and variable-ratio schedules of reinforcement

Abstract

Pigeons were trained to respond on either a fixed- or a variable-ratio schedule of reinforcement. After responding had stabilized, a visual stimulus change was presented after either 20% or 80% of the ratio had been completed. The duration of the stimulus was equal to the time it took the subjects to complete an additional 10% of the ratio. Presentation of the stimulus early in the ratio inhibited responding on the variable, but not on the fixed-ratio schedule. A stimulus change after 80% of the ratio had been completed, only produced response enhancement on the variable-ratio schedule. The effects of stimulus intrusion on ratio schedules were determined by a) the temporal proximity between stimulus intrusion and reinforcement presentation, and b) the contingencies of the operant baseline.