Twelve college students received conditional discrimination training with nonarbitrary and arbitrary stimuli, and derived comparative and transformation of function tests with a think-aloud condition across 2 experiments. Participants who failed these tests received remedial verbal operant training. Four control participants received verbal operant training alone. Across both experiments, only 1 participant passed the derived comparative test after conditional discrimination training. However, all participants passed derived comparative tests and 11 out of 12 participants passed transformation of function tests following verbal operant training, including the 4 control participants. Participants who passed derived comparative tests engaged in a high percentage of correct vocalizations during the think-aloud condition, while participants who failed did not. These results suggest that mediating verbal behavior could have played a crucial role in participants' responses during derived stimulus relations tests.
Keywords: comparative relations; conditional discrimination; frames of comparison; mediation; verbal behavior.
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