Abstract
Communicative pointing is a human specific gesture which allows sharing information about a visual item with another person. It sets up a three-way relationship between a subject who points, an addressee and an object. Yet psychophysical and neuroimaging studies have focused on non-communicative pointing, which implies a two-way relationship between a subject and an object without the involvement of an addressee, and makes such gesture comparable to touching or grasping. Thus, experimental data on the communicating function of pointing remain scarce. Here, we examine whether the communicative value of pointing modifies both its behavioral and neural correlates by comparing pointing with or without communication. We found that when healthy participants pointed repeatedly at the same object, the communicative interaction with an addressee induced a spatial reshaping of both the pointing trajectories and the endpoint variability. Our finding supports the hypothesis that a change in reference frame occurs when pointing conveys a communicative intention. In addition, measurement of regional cerebral blood flow using H2O15 PET-scan showed that pointing when communicating with an addressee activated the right posterior superior temporal sulcus and the right medial prefrontal cortex, in contrast to pointing without communication. Such a right hemisphere network suggests that the communicative value of pointing is related to processes involved in taking another person's perspective. This study brings to light the need for future studies on communicative pointing and its neural correlates by unraveling the three-way relationship between subject, object and an addressee.
Highlights
The pointing gesture is used to share information about an object with another person [1,2]
The analysis of spatial parameters revealed a significant shift of the direction of pointing toward the Left and Right addressees, for Left communicative pointing (CP) and Right CP trajectories respectively
The comparison of CP and non-communicative pointing (NCP) in this study reveals that the communicative interaction with an addressee yields behavioral and neural modifications
Summary
The pointing gesture is used to share information about an object with another person [1,2]. The absence of or the delay in the emergence of pointing behavior in autistic spectrum conditions led to the hypothesis of a deficit in a ‘Shared Attention Mechanism’ (SAM) [15,16] In this model, two representations are combined: a first representation that takes into account the relation between the subject and the object (‘I see X’, first person’s perspective), and a second representation that specifies the relationship of another agent on the same object (‘He/she sees X’, third person’s perspective). This hypothesis has brought considerable attention in the domain of social cognition; experimental evidence has yet to be provided
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