Ageing, working memory, and mental imagery: Understanding gestural communication in younger and older adults.

Ageing has effects both on language and gestural communication skills. Although gesture use is similar between younger and older adults, the use of representational gestures (e.g., drawing a line with fingers on the air to indicate a road) decreases with age. This study investigates whether this change in the production of representational gestures is related to individuals' working memory and/or mental imagery skills. We used three gesture tasks (daily activity description, story completion, and address description) to obtain spontaneous co-speech gestures from younger and older individuals ( = 60). Participants also completed the Corsi working memory task and a mental imagery task. Results showed that although the two age groups' overall gesture frequencies were similar across the three tasks, the younger adults used relatively higher proportions of representational gestures than the older adults only in the address description task. Regardless of age, the mental imagery but not working memory score was associated with the use of representational gestures only in this task. However, the use of spatial words in the address description task did not differ between the two age groups. The mental imagery or working memory scores did not associate with the spatial word use. These findings suggest that mental imagery can play a role in gesture production. Gesture and speech production might have separate timelines in terms of being affected by the ageing process, particularly for spatial content.