Effects of distributed practice and criterion level on word retrieval in aphasia.

This study examined how the distribution and amount of practice affect word retrieval in aphasia as well as how such factors relate to the efficiency of learning. The central hypothesis was that factors that enhance the learning of new knowledge also enhance persistent access to existing, but inconsistently available, word representations. The study evaluated the impact of learning principles on word retrieval by manipulating the timing and amount of retrievals for items presented for naming. Nine people with chronic aphasia with naming impairment completed the experiment. Training materials involved proper noun entities assigned to six conditions formed by crossing a 2-level factor of spacing of sessions, i.e., intersession interval (1 day versus 7 days between sessions) with a 3-level factor of number of correct retrievals per item per session, i.e., criterion level (Criterion-1, Criterion-2, and Criterion-4). Each intersession interval condition comprised three training sessions and a one-month retention test. Increasing the criterion level enhanced naming performance after short (1 day, 7 days) and long (one month) retention intervals, but these advantages came at the cost of many additional training trials. In most cases, later naming success was superior when the same number of correct retrievals of an item was distributed across multiple sessions rather than administered within one session. The substantial advantages for across-session spacing were gained at little cost in terms of additional training trials. At one-month retention, naming accuracy was numerically but not significantly higher in the 7-day versus 1-day intersession interval condition. Implications for theories of lexical access and naming treatment in aphasia are discussed.