Promoting visual long-term memories: When do we learn from repetitions of visuospatial arrays?

Repeated exposure is assumed to promote long-term learning. This is demonstrated by the so-called “Hebb-effect”: when short lists of verbal or spatial materials are presented sequentially for an immediate serial recall test, recall improves with list repetition. This repetition benefit, however, is not ubiquitous. Previous studies found little or no performance improvement for repetitions of visuospatial arrays (e.g., arrays of colored squares). Across eight experiments with college students and Prolific samples, we investigated which factors promote visuospatial learning by testing all combinations of variables distinguishing between visual-array tasks (brief + simultaneous presentation + a single recognition test) and tasks showing the Hebb effect (slow + sequential presentation + recall test probing all items). Participants profited from repetitions when all items were tested with a recall procedure, but not if the test consisted of recognition. Hence, the key to promote long-term learning is to recall all of the memorized information over the short-term.