The actual and potential use of gestures for communication in aphasia

Abstract

Background: Two main conflicting positions exist concerning the relationship of gesture and speech. The first claims that gesture and speech constitute a single bimodal production process that leads to an impairment of both communication channels in the case of aphasia. The second accounts for two independent but tightly coordinated processes with a trade-off relationship of gesture and speech. According to the latter assumption, speakers who have aphasia should be able to compensate for their verbal deficiencies through gesture. Studies provide evidence for both accounts. Furthermore, non-verbal capacities like semantic processing or manual praxis have been shown to influence the gestural performance of speakers who have aphasia.

Aims: The first aim of the current study was to clarify the relationship between gesture and speech production in aphasia by exploring how much information speakers with aphasia conveyed by gesture versus speech in narrations. The second aim was to evaluate if these speakers make use of their full communicative potential through gesture. We compared gesture use in a verbal narration with gesture use in a silent condition, where participants were not allowed to speak. Furthermore, the influence of language and non-verbal cognitive capacities on gesture was examined.

Methods & Procedures: Sixteen participants with varying degrees of aphasia severity retold short video clips in a verbal and a silent condition. In the latter, participants were asked to retell the stories by exclusively using gestures. Subsequently, healthy speakers judged the comprehensibility of gestures and of the spoken expression in the verbal narration in a forced-choice recognition task. Comprehensibility scores were compared between conditions and influencing linguistic and non-verbal factors were evaluated.

Outcomes & Results: In the verbal condition, two participants conveyed more information through gesture than through spoken expression. Furthermore, half of the participants could augment gestural comprehensibility in the silent condition. Communicative efficiency of gesture was predicted by the pantomime-to-command test.

Conclusions: Findings support the view that gesture and speech have a trade-off relationship resulting from two separate but tightly coordinated communication channels. Not all participants fully exploited their gestural potential in the verbal condition. Some of them produced more informative gestures in the silent condition, where they had been explicitly asked to solely convey messages through gesture. Among different linguistic and non-verbal tests, pantomime of object use, which is a test of limb apraxia, was the main influencing factor on the comprehensibility of co-speech and speech-replacing gesture.

Keywords:

• Gesture
• Non-verbal communication
• Aphasia
• Pantomime
• Apraxia
• Non-verbal semantic processing.

This work was funded by the German Research Foundation (DFG GO 968/3-3). Reha-Hilfe e.V. is thanked for financial support. We appreciate the participants for their collaboration. Hanna Jakob is thanked for collecting the comprehensibility data. We are grateful for the valuable comments of Prof. Jan De Ruiter and one anonymous reviewer.

Notes

2. ¹ 0 = no comprehensible utterances and manifest impairments in comprehension; 1 = patient communicates through incomplete, mostly incomprehensible utterances; the listener has to guess or ask for more information; 2 = talking about familiar topics is possible with help of the communication partner, but the patient is frequently not able to convey the message; 3 = the patient is able to talk about problems of everyday life with only little support and conversation is difficult due to obvious language impairments; 4 = the fluency of speech production is reduced and/or some language impairments exist; 5 = no disturbance of verbal communication and/or minimal difficulties with speaking and/or patient reports difficulties with language that are not evident for the communication partner (paraphrased from AAT manual; Huber et al., 1983).