Gesturing by aphasic speakers, how does it compare?

Gesturing by aphasic speakers, how does it compare? Lisette Mol (l.mol@uvt.nl) 1 Emiel Krahmer (e.j.krahmer@uvt.nl) 1 Mieke van de Sandt-Koenderman (m.sandt@rijndam.nl) 2 Tilburg Center for Cognition and Communication (TiCC), School of Humanities, Tilburg University P.O. Box 90135, NL-5000 LE Tilburg, The Netherlands Rotterdam Neurorehabilitation Research (RoNeRes) Rijndam Rehabilitation Centre, and Erasmus MC, dept. of Rehabilitation Medicine, P.O. Box 23181, NL-3001 KD, Rotterdam, The Netherlands Abstract gesture and speech production are complementary and can compensate one another, which also underlies the Tradeoff Hypothesis. This hypothesis states that “when speaking gets harder, speakers will rely relatively more on gestures”, and vice versa (De Ruiter, Bangerter, & Dings, in press). Yet De Ruiter et al. found only little evidence that people gesture more when speech is harder. Rather, they found that gesture and speech tended to express similar types of information, consistent with the idea that gesture and speech are two sides of a coin. We compared gesturing by aphasic speakers to that of healthy controls, to see if gesture degrades with speech, or can be compensatory. We found that gestures by aphasics were less informative than those of controls, and that gestures by people with severe aphasia were less informative than those by people with mild aphasia. We also found that aphasics tended to use fewer representation techniques in gesture than healthy controls who were asked to use gesture instead of speech. These results suggest that in aphasia, gesture tends to degrade with speech, rather than it being compensatory. This implies that the processes underlying speech and gesture production may be tightly linked or shared. Gesture Production and Aphasia Keywords: Aphasia, Gesture. Introduction Gesture and Speech Production When speaking, people oftentimes produce hand gestures, which are closely linked to their speech temporally (Chui, 2005), structurally (Kita & Ozyurek, 2003), and semantically (e.g. McNeill, 2005). For example, when asking a sales clerk for a sweater, gestures may indicate that we prefer a V-neck, a large front pocket, or one just like the one we are wearing. Both the production of speech and the production of gestures seem to be part of a speaker’s communicative effort (Kendon, 2004). Although different functions of gesture have also been recognized, such as facilitating speech production (Krauss, 1998) and supporting cognition (Melinger & Kita, 2007), much empirical evidence has been gathered for the idea that gestures are communicative and are intended as such (e.g. Alibali, Heath, & Myers, 2001; Beattie & Shovelton, 1999). McNeill (2005) argued that speech and gesture co-express idea units, which develop themselves into utterances. That is, that they are two sides of the same coin. In support of this idea, So, Kita, and Goldin-Meadow (2009) found that if information was lacking in speech, it tended to be missing in gesture as well. However, Melinger and Levelt (2004) found that speakers sometimes divide the content of their message across gesture and speech. They found that if critical spatial information was expressed in gesture, it was more likely to be omitted in speech. This goes well with the idea that In light of the question of whether gesture and speech compensate for one another, it is interesting to study what happens to gesture when speech breaks down, such as in aphasia. Aphasia is an acquired language disorder caused by brain damage. It not only affects verbal expression, but has an impact on all language modalities. In our current study we focus on aphasic people who have severe to mild problems expressing themselves verbally. Numerous studies have shown that aphasic people still gesture spontaneously and frequently (Rose, 2006). People with fluent aphasia may even gesture more informatively than non-aphasic speakers (Carlomagno, Pandolfi, Martini, Di Iasi, & Cristilli, 2005). Case studies and clinical experience confirm that some aphasic speakers use gesture effectively to communicate (e.g. Goodwin, 2002). This suggests that they may be able to partly compensate for their speech impairment with gesture. Yet does this mean their gesturing is unimpaired? Studies that looked at gesturing by people with aphasia have mostly used the gesture coding scheme developed by McNeill (2005). For example, Carlomagno et al. looked at the informativeness of iconic gestures, which are gestures that mostly depict entities or movements. Yet when producing an iconic gesture, there are still different ways in which we can depict (Cienki & Muller, 2008). For example, if we want to depict a sweater, we can outline the shape of it, or we can pretend to put it on. And if we are talking about a car, we can move our hands as though steering it, or we can let our hand represent the car, depicting its path with our hand movement. So there is more to say about a gesture’s