Gesturing by speakers with aphasia: how does it compare?

To study the independence of gesture and verbal language production. The authors assessed whether gesture can be semantically compensatory in cases of verbal language impairment and whether speakers with aphasia and control participants use similar depiction techniques in gesture.

The informativeness of gesture was assessed in 3 forced-choice studies, in which raters assessed the topic of the speaker's message in video clips of 13 speakers with moderate aphasia and 12 speakers with severe aphasia, who were performing a communication test (the Scenario Test). Both groups were compared and contrasted with 17 control participants, who either were or were not allowed to communicate verbally. In addition, the representation techniques used in gesture were analyzed.

Gestures produced by speakers with more severe aphasia were less informative than those by speakers with moderate aphasia, yet they were not necessarily uninformative. Speakers with more severe aphasia also tended to use fewer representation techniques (mostly relying on outlining gestures) in co-speech gesture than control participants, who were asked to use gesture instead of speech. It is important to note that limb apraxia may be a mediating factor here.

These results suggest that in aphasia, gesture tends to degrade with verbal language. This may imply that the processes underlying verbal language and co-speech gesture production, although partly separate, are closely linked.