The Roles of Retrieval Practice Versus Errorless Learning in Strengthening Lexical Access in Aphasia

The purpose of this study was to determine how 2 methods known to improve naming impairment in aphasia (i.e., retrieval practice and errorless learning) affect lexical access. We hypothesized that instances of naming during retrieval practice use and strengthen item-specific connections in each of 2 stages of lexical access: Stage 1, meaning-to-word connections, and Stage 2, word-to-phonology connections. In contrast, errorless learning prioritizes opportunities for repeating words, which we expect to primarily strengthen item-specific connections in Stage 2 because repetition circumvents the need for semantically driven word retrieval.

We tested the outcomes of retrieval practice versus errorless learning training for items that were selected because the naming errors they elicited suggested weakened connections at Stage 1 or at Stage 2 of lexical access for each of 10 individuals with chronic aphasia. Each participant's Stage 1 items and Stage 2 items were divided evenly between the 2 training conditions. Naming tests were administered 1 day and 1 week after training to assess retention of training gains. We also examined whether the participants' pretraining naming error profiles were associated with the relative efficacy of retrieval practice versus errorless learning.

The posttraining naming tests showed an advantage of retrieval practice over errorless learning for Stage 1 items and an advantage of errorless learning over retrieval practice for Stage 2 items. In addition, greater percentages of phonological error naming responses prior to training were associated with greater posttraining accuracy in the errorless learning condition relative to the retrieval practice condition.

The findings suggest that the advantage of retrieval practice for naming impairment in aphasia largely results from greater strengthening of practiced semantic-lexical connections compared with errorless learning, which prioritizes repetition and, therefore, mainly confers strengthening of practiced lexical-phonological connections. Understanding how specific training conditions improve naming can help predict the relative efficacy of each method for individuals with aphasia.