When two memories can and cannot be retrieved concurrently.

We examined whether two memories can be retrieved concurrently from long-term memory. In Experiment 1, the subjects recalled words, either from two categories--alternating between the two--or from just one category. In Experiment 2, the subjects recalled two words belonging to either the same category or different categories, and the category prompts for these two responses appeared either simultaneously or successively. The results of both studies are consistent with the view that two items from different categories must be retrieved serially, whereas two items from the same category can be retrieved in parallel.