Previous work suggests that the communicative behavior
of older adults differs systematically from that of younger
adults. For instance, older adults produce significantly fewer
representational gestures than younger adults in monologue
description tasks (Cohen & Borsoi, 1996; Feyereisen &
Havard, 1999). In addition, older adults seem to have more
difficulty than younger adults in establishing common ground
(i.e. knowledge, assumptions, and beliefs mutually shared
between a speaker and an addressee, Clark, 1996) in speech
in a referential communication paradigm (Horton & Spieler,
2007). Here we investigated whether older adults take such
common ground into account when designing multi-modal
utterances for an addressee. The present experiment com-
pared the speech and co-speech gesture production of two age
groups (young: 20-30 years, old: 65-75 years) in an inter-
active setting, manipulating the amount of common ground
between participants.
Thirty-two pairs of nave participants (16 young, 16 old,
same-age-pairs only) took part in the experiment. One of the
participants (the speaker) narrated short cartoon stories to the
other participant (the addressee) (task 1) and gave instruc-
tions on how to assemble a 3D model from wooden building
blocks (task 2). In both tasks, we varied the amount of infor-
mation mutually shared between the two participants (com-
mon ground manipulation). Additionally, we also obtained a
range of cognitive measures from the speaker: verbal work-
ing memory (operation span task), visual working memory
(visual patterns test and Corsi block test), processing speed
and executive functioning (trail making test parts A + B) and
a semantic fluency measure (animal naming task). Prelimi-
nary data analysis of about half the final sample suggests that
overall, speakers use fewer words per narration/instruction
when there is shared knowledge with the addressee, in line
with previous findings (e.g. Clark & Wilkes-Gibbs, 1986).
This effect is larger for young than for old adults, potentially
indicating that older adults have more difficulties taking com-
mon ground into account when formulating utterances. Fur-
ther, representational co-speech gestures were produced at the
same rate by both age groups regardless of common ground
condition in the narration task (in line with Campisi & zyrek,
2013). In the building block task, however, the trend for the
young adults is to gesture at a higher rate in the common
ground condition, suggesting that they rely more on the vi-
sual modality here (cf. Holler & Wilkin, 2009). The same
trend could not be found for the old adults. Within the next
three months, we will extend our analysis a) by taking a wider
range of gesture types (interactive gestures, beats) into ac-
count and b) by looking at qualitative features of speech (in-
formation content) and co-speech gestures (size, shape, tim-
ing). Finally, we will correlate the resulting data with the data
from the cognitive tests.
This study will contribute to a better understanding of the
communicative strategies of a growing aging population as
well as to the body of research on co-speech gesture use in
addressee design. It also addresses the relationship between
cognitive abilities on the one hand and co-speech gesture
production on the other hand, potentially informing existing
models of co-speech gesture production.