Getting to the Point: The Influence of Communicative Intent on the Kinematics of Pointing Gestures

Getting to the Point: The Influence of Communicative Intent on the Kinematics of Pointing Gestures David Peeters (david.peeters@mpi.nl) Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands International Max Planck Research School for Language Sciences, Nijmegen, The Netherlands Radboud University, Donders Institute for Brain, Cognition, and Behaviour, Nijmegen, The Netherlands Mingyuan Chu (mingyuan.chu@mpi.nl) Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands Judith Holler (judith.holler@mpi.nl) Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands School of Psychological Sciences, University of Manchester, UK Asli Ozyurek (asli.ozyurek@mpi.nl) Radboud University, Center for Language Studies, Nijmegen, The Netherlands Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands Peter Hagoort (peter.hagoort@mpi.nl) Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands Radboud University, Donders Institute for Brain, Cognition, and Behaviour, Nijmegen, The Netherlands Abstract In everyday communication, people not only use speech but also hand gestures to convey information. One intriguing question in gesture research has been why gestures take the specific form they do. Previous research has identified the speaker-gesturer’s communicative intent as one factor shaping the form of iconic gestures. Here we investigate whether communicative intent also shapes the form of pointing gestures. In an experimental setting, twenty-four participants produced pointing gestures identifying a referent for an addressee. The communicative intent of the speaker- gesturer was manipulated by varying the informativeness of the pointing gesture. A second independent variable was the presence or absence of concurrent speech. As a function of their communicative intent and irrespective of the presence of speech, participants varied the durations of the stroke and the post-stroke hold-phase of their gesture. These findings add to our understanding of how the communicative context influences the form that a gesture takes. Keywords: Pointing Gesture; Communicative Intent; Gesture Production; Action Planning; Deixis. Introduction In everyday communication, people not only use speech but also meaningful hand gestures to convey information. One of the most intriguing questions in gesture research has been why such gestures take the physical form they do (Bavelas et al., 2008; Gerwing & Bavelas, 2004; Krauss, Chen, & Gottesman, 2000). The main focus so far in answering this question has been on gestures iconic in nature, i.e., gestures that in form and manner of execution visually resemble the simultaneously expressed meaning of the linguistic part of an utterance (McNeill, 1985), such as moving up and down one’s hand when talking about a basketball game. Typically, such studies have varied aspects of the communicative context, such as the visibility of gestures or the knowledge speaker and listener mutually share. Amongst other things, these studies have shown that speakers design their gestures for particular recipients and produce more (e.g., Alibali, Heath, & Myers, 2001; Bavelas et al., 2008) as well as larger and more precise gestures when communicative intentions are enhanced (e.g., Gerwing & Bavelas, 2004; Holler & Stevens, 2007). Thus, iconic co-speech gestures seem closely linked to the speaker’s specific communicative intent, and the particular form an iconic gesture takes depends on the context-bound communicative relation between speaker and addressee (see Holler & Wilkin, 2011). In contrast, it is unclear how the form of pointing gestures changes as a function of the gesturer’s communicative intent. Pointing is a foundational building block of human communication (Kita, 2003) and allows us to directly connect our communication to the material world that surrounds us (Clark, 2003). Pointing has received much attention in the literature from an ontogenetic viewpoint because of its role in paving the way for the acquisition of language (Butterworth, 2003; Carpenter, Nagell, & Tomasello, 1998; Tomasello, Carpenter, & Liszkowski, 2007), as well as from a phylogenetic viewpoint with respect to declarative pointing being a uniquely human form of communication in a natural environment (Call & Tomasello, 1994; Kita, 2003; Tomasello et al., 2007). In contrast, the exact form parameters that people vary in the production of pointing gestures in human adult communication remain largely unknown. Therefore, the present study aims at contributing further to our