Molecular Analysis of Conditional Discriminations: The Sequential Pattern of Human Learning

Whether the acquisition of conditional relations occurs simultaneously or sequentially is often obscured by global accuracy measures. The present study analyzed the acquisition of conditional discriminations in humans using a molecular, trial-by-trial approach. Three undergraduate students were trained on 12 visual conditional relations, divided into two sets (AB and BC), using an arbitrary zero-delay matching-to-sample (MTS) procedure. Results showed that all participants reached the acquisition criteria for each conditional relation at different moments during training. The cumulative frequency curves for each relation showed minimal overlap, indicating a clear sequential pattern of acquisition where relations were learned one by one. These findings suggest that average accuracy scores can mask individual learning trajectories and that reinforcement histories develop uniquely for each relation during training. Understanding these fundamental learning processes in MTS is a crucial step toward elucidating the mechanisms governing the formation of equivalence classes and possibly improving the efficiency with which these classes are formed.