Do the hands have it? The facilitation effects of arm and hand gesture on word retrieval in aphasia

Background: There is considerable disagreement in the literature concerning the function of co-verbal gesture. Studies of the relationship between speech and gesture have employed an array of methods to investigate the origin and functions of arm and hand gesture. Commonly, these studies have utilised an experimental design to examine possible speech facilitation effects. However there is a need to examine spontaneous gesture production and its effect on speech production, as evidence suggests that natural gesture production is distinct from that produced under test conditions. Aims: To investigate the possible facilitation effects of spontaneously generated arm and hand gestures during word retrieval difficulty in people with aphasia. Methods Procedures: Conversational samples 20 minutes long were acquired from 18 participants with chronic aphasia. Verbal utterances were transcribed for word retrieval difficulty, resolved word retrieval difficulty, and fluent speech production. The transcription was augmented with all arm and hand gestures produced by the participants. Gestures were segmented into gesture units and classified into types. A second rater classified 20% of the samples for gesture type, occurrence of word retrieval difficulty, and whether the difficulty was successfully resolved or not. Consensus ratings were carried out where disagreement occurred. Variables were paired for comparison using a series of non-parametric Wilcoxon Signed-Ranks Tests. Outcomes Results: Gesture production was significantly higher during instances of word retrieval difficulties. The resolution of word retrieval difficulty was significantly more frequent with a gesture present. Crucially, there was no significant difference between the amounts of gesture produced during resolved, as compared to unresolved, word retrieval difficulties. However performance in the group was variable. Five individuals produced over 50% more gesture during resolved word retrieval events than during unresolved. Post-hoc examination of the linguistic characteristics of these five participants suggested they had a specific phonological level impairment. Conclusions: Gesture production is multifunctional for people with aphasia. People with mild aphasia, who have the majority of their linguistic resources still accessible, are likely to experience facilitation from gesture production, and hence gesture treatment maybe an appropriate and potent therapy focus. Some individuals with severe language impairment are capable of using many rich, communicative gestures. Such gesture expression should be explored as a viable component of a ototal communicationo therapeutic approach for those individuals.