Failure to read motor intentions from gaze in children with autism.

A core feature of autism is the abnormal use of gaze to attribute mental states to others, and thus to predict others' behaviour. An untested idea is whether this dysfunction is confined to mental states having a propositional content, such as beliefs and desire or extends to motor intentional states which allow one to make inferences about the actions of others. This study used kinematics to examine the ability to use gaze to inform one about the motor states of another in normal and autistic children. In each trial two participants, a model and an observer, were seated facing each other at a table. In three experimental blocks the model was requested to grasp a stimulus, to gaze towards the same stimulus, and to gaze away from the stimulus without performing any action. The task for the observer was to grasp the stimulus after having watched the model perform her task. We observed that normal children showed facilitation effects in terms of movement speed following the observation of the model grasping or simply gazing at the object. In contrast, autistic children did not show any evidence of facilitation in these conditions. Neither normal nor autistic children showed evidence of facilitation when the model's gaze was not directed towards the stimulus. These findings demonstrate that, in contrast to normal children, children with autism fail to use information from the model's action or gaze to plan their subsequent action, and that in autism the inability to use of another person's gaze produces a lack of understanding of the motor intention of others.