Retrieval practice and spacing effects in multi-session treatment of naming impairment in aphasia

Retrieval practice and spacing are two factors shown to enhance learning in basic psychological research. The present study investigated the clinical applicability of these factors to naming treatment in aphasia. Prior studies have shown that naming treatment that provides retrieval practice (i.e., practice retrieving names for objects from semantic memory) improves later naming performance in people with aphasia (PWA) more so than repetition training. Repetition training is a common form of naming treatment that can support errorless production of names for objects, but it does not provide retrieval practice. Prior work has also demonstrated enhanced naming treatment benefit in PWA when an item's training trials are separated by multiple intervening trials (i.e., spacing) compared to only one intervening trial (i.e., massing). However, in those studies, items were only trained in one session. Also, the effects of the learning factors were probed after one day and one week. The goal of the present study was to examine the effects of retrieval practice and spacing in a more clinically-inspired schedule of delivery and to assess the effects of the learning factors at retention intervals of greater functional significance. Matched sets of errorful items for each of four PWA were presented for multiple trials of retrieval practice or repetition in a spaced or massed schedule in each of multiple training sessions. Mixed regression analyses revealed that retrieval practice outperformed repetition, and spacing outperformed massing, at an initial post-treatment test administered after one week. Furthermore, the advantage for retrieval practice over repetition persisted at a follow-up test administered after one month. The potential clinical relevance of retrieval practice and spacing for multi-session interventions in speech-language treatment is discussed.