Associative Unitization via Semantic Relatedness Benefits Episodic Recognition of Component Elements

It has been proposed that although unitization benefits associative episodic memory, such benefits may exact a cost of poorer subsequent memory for the individual component elements forming these associations. However, unitization effects on item memory may be a function of whether items were unitized in a top-down fashion (i.e., through encoding instructions) or in a bottom-up fashion (through inherent semantic relationships between the associated items). We hypothesized that semantic relatedness unitization would benefit item recognition due to processing fluency that affords availability of more encoding resources. In two experiments, we tested how relatedness unitization of object pictures at encoding affected subsequent item recognition. The first experiment used a between-subject inclusion/exclusion paradigm, while the second experiment used a within-subject three-alternative choice recognition test. Results of both experiments revealed that semantic relatedness unitization benefited item memory. However, both accuracy patterns and error analyses indicated that such relatedness-based unitization improved memory for an item’s gist (i.e., its categorical identity), but not for its visual details. This indicates that that associative relatedness at encoding strengthens representations of the semantic identity of individual stimuli, but not necessarily of their perceptual details, possibly because of enhanced semantic elaboration at encoding.