Eye Fixations in Delayed Matching-to-Sample Task as Predictors of Stimuli Class Formation in MTS Tasks

This study examined whether eye fixation duration on sample stimuli predicts success in equivalence class formation during matching-to-sample (MTS) tasks with varying delays. Nine typically developing adults completed conditional discrimination training using a one-to-many (OTM) structure to establish four three-member equivalence classes. Each class was trained under a different delay condition: simultaneous MTS, 0-s, 2-s, or 4-s delays between sample offset and comparison onset. Eye movements were recorded throughout training to assess observing behavior. Seven participants met the learning criterion and demonstrated equivalence class formation. The delay condition did not significantly affect the acquisition or emergence of equivalence or symmetry relations. Similarly, sample fixation durations did not significantly differ across delay conditions. However, fixation durations were longer in early training blocks, suggesting a practice effect. A strong positive correlation between sample response latency and fixation duration also emerged, supporting the interpretation that latency may reflect engagement time. These findings challenge the view that increased delay intervals inherently enhance learning by extending sample observation and instead highlight the value of direct eye-tracking measures in understanding observing behavior and its relation to stimulus control.