Meeter, M., Shohamy, D. & Myers, C.E. (2009).
Acquired equivalence changes stimulus representations.
Journal of the Experimental Analysis of Behavior, 91, 127-141.
Acquired equivalence is a paradigm in which generalization is increased between two superficially dissimilar stimuli (or antecedents) that have
previously been associated with similar outcomes (or consequents). Several possible mechanisms have been proposed, including changes in stimulus
representations, either in the form of added associations or a change of feature salience. A different way of conceptualizing acquired equivalence is
in terms of strategic inference: Confronted with a choice on which it has no evidence, the organism may infer from its history of reinforcement what
the best option is, and that inference is observed as acquired equivalence. To test this account, we combined an incremental learning task with an
episodic memory test. Drawings of faces were made equivalent through incremental acquired equivalence training, and then paired with words in an
episodic study paradigm. When participants were asked to recognize specific face-word pairings, they confused faces more often when they had been made
equivalent. This suggests that prior acquired equivalence training does influence how memories are coded. We also tested whether this change in coding
reflected acquisition of new associations, as suggested by the associative mediation account, or whether stimuli become more similar through a
reweighting of stimulus features, as assumed by some categorization theories. Results supported the associative mediation view. We discuss similarities
between this view and exemplar theories of categorization performance.
Key words: memory, learning, hippocampus, conditioning, acquired equivalence, humans