Communicative knowledge pervasively influences sensorimotor computations

Abstract

Referential pointing is a characteristically human behavior, which involves moving a finger through space to direct an addressee towards a desired mental state. Planning this type of action requires an interface between sensorimotor and conceptual abilities. A simple interface could supplement spatially-guided motor routines with communicative-ostensive cues. For instance, a pointing finger held still for an extended period of time could aid the addressee’s understanding, without altering the movement’s trajectory. A more complex interface would entail communicative knowledge penetrating the sensorimotor system and directly affecting pointing trajectories. We compare these two possibilities using motion analyses of referential pointing during multi-agent interactions. We observed that communicators produced ostensive cues that were sensitive to the communicative context. Crucially, we also observed pervasive adaptations to the pointing trajectories: they were tailored to the communicative context and to partner-specific information. These findings indicate that human referential pointing is planned and controlled on the basis of partner-specific knowledge, over and above the tagging of motor routines with ostensive cues.

Recipient Design in Communicative Pointing

“…This study adds to previous work on communicative pointing by quantifying the informative value of those movements. For instance, it is known that communicative pointing results in more emphatic pointing stroke duration (Peeters, Hagoort, & Ozyurek, ) and longer holding times than those evoked in control conditions (Murillo Oosterwijk et al., ). Furthermore, the trajectories of communicative pointing movements are influenced by the spatial location of the addressee (Murillo Oosterwijk et al., ).…”

“…For instance, it is known that communicative pointing results in more emphatic pointing stroke duration (Peeters, Hagoort, & Ozyurek, ) and longer holding times than those evoked in control conditions (Murillo Oosterwijk et al., ). Furthermore, the trajectories of communicative pointing movements are influenced by the spatial location of the addressee (Murillo Oosterwijk et al., ). Here, we show that those trajectory modifications increase the informational value of the pointing movement, when seen from the spatial perspective of the addressee, which was not yet implied by the previous observations on this data set (Murillo Oosterwijk et al., ).…”

“…Murillo Oosterwijk et al. () report a significant increase in trajectory variability, which could have countered the to‐be‐expected benefits from the increased mean differences. Increased legibility can thus not be taken for granted but must be analyzed explicitly.…”

“…These observations suggest that communicators increase the informational value of the movement by pointing over a longer time, thereby allowing the addressee to accumulate more sensory evidence against the intrinsic noise in the sensorimotor system (Faisal, Selen, & Wolpert, ). Beyond differences in timing and end‐point, recent studies have shown that the presence of communicative intent during pointing movements also influences movement trajectories in an addressee‐dependent fashion (Cleret de Langavant et al., ; Murillo Oosterwijk et al., ; Ozyurek, ). Murillo Oosterwijk et al.…”

“…Murillo Oosterwijk et al. () had participants point out referents for an addressee standing either to their left or right side. The main finding was that pointing trajectories were influenced by the spatial location of the addressee.…”