Assessing Stimulus Control in a Discrimination Task with Compound Stimuli: Evaluating Testing Procedures and Tracking Eye Fixations

Abstract

Experiments with pigeons have suggested that the way stimuli are arranged in tests affects the demonstration of the stimulus control established during training. The present study aimed to replicate these findings with humans exposed to a simultaneous-discrimination task with compound stimuli. Adults were exposed to a discrimination task, and their eye fixations were recorded. Two compound stimuli were used: a triangle and a red circle, and a square and a green circle. During Phase 1, responses to the first compound were reinforced, and during Phase 2, these contingencies were reversed. Following training in each phase, the components of the stimulus compound were separated and presented across different tests to assess stimulus control by each stimulus component. Participants tended to choose the component on which their eyes had most frequently fixated during training. However, the S+ component that was associated with fewer fixations also controlled participants’ choices. Results on tests replicate previous findings with pigeons. Possible effects of peripheral vision are discussed.