The role of covert retrieval in working memory span tasks: Evidence from delayed recall tests

The current study examined delayed recall of items that had been processed during simple and complex span tasks. Three experiments were reported showing that despite more items being recalled initially from a simple span task (i.e., word span) than a complex span task (i.e., operation span), on a delayed recall test more items were recalled that had initially been processed during the complex span task. This delayed recall advantage for items processed during complex span tasks persisted when subjects were encouraged to process the items deeply during the initial span task (Experiment 2), and when initial recall during the span task was precluded (Experiment 3). The covert retrieval model explains these data as being the result of subjects maintaining items in working memory during complex span tasks by covertly retrieving them during the processing phases of the tasks. These covert retrieval attempts provide distributed practice retrieving items from long-term memory, creating effective retrieval cues for later delayed recall that are not created during simple span tasks. The covert retrieval model was supported by data showing that words presented in earlier serial positions during operation span, which had the greatest likelihood of being covertly retrieved, were most likely to be recalled on the delayed recall test. These data support the notion that complex working memory span tasks share considerable processing overlap with episodic memory tasks.