The role of transients in action observation

Attention allocation in complementary joint action: How joint goals affect spatial orienting

When acting jointly, individuals often attend and respond to the same object or spatial location in complementary ways (e.g., when passing a mug, one person grasps its handle with a precision grip; the other receives it with a whole-hand grip). At the same time, the spatial relation between individuals' actions affects attentional orienting: one is slower to attend and respond to locations another person previously acted upon than to alternate locations ("social inhibition of return", social IOR). Achieving joint goals (e.g., passing a mug), however, often requires complementary return responses to a co-actor's previous location. This raises the question of whether attentional orienting, and hence the social IOR, is affected by the (joint) goal our actions are directed at. The present study addresses this question. Participants responded to cued locations on a computer screen, taking turns with a virtual co-actor. They pursued either an individual goal or performed complementary actions with the co-actor, in pursuit of a joint goal. Four experiments showed that the social IOR was significantly modulated when participant and co-actor pursued a joint goal. This suggests that attentional orienting is affected not only by the spatial but also by the social relation between two agents' actions. Our findings thus extend research on interpersonal perception-action effects, showing that the way another agent's perceived action shapes our own depends on whether we share a joint goal with that agent.

Biological motion elicits between-person Inhibition of Return in temporal and spatial movement parameters

The present study was designed to gain a deeper understanding of the processing of biological motion stimuli. To this end, we investigated if the inhibition of return (IoR) effect emerges in initiation times and trajectories of pointing movements to targets in left and right space where the preceding cues were pointing movement of a human model or a dot with the same biological motion. Targets were randomly presented in the same or opposite side from the direction of the motion cue. It was hypothesised that the visuomotor system should resonate with the biological motion of a dot, but that the human model should exaggerate the effect. Thus, the human model should trigger stronger attention shifts compared with the dot model and lead to more robust IoR effects in both spatial (movement) and temporal parameters of the observer's pointing responses. Initiation times and the spatial parameters (angle of the hand trajectory) of the pointing movements were analysed. Results indicate that facilitation and IoR effects triggered by human and dot stimuli did not differ. Based on these findings, it seems that the crucial feature of motion cues that generate shifts in attention is biological motion, rather than human appearance per se.

Feasibility of action observation effect on gait and mobility in idiopathic normal pressure hydrocephalus patients

Action observation (AO) has been proved to be of benefit in several neurological conditions, but no study has previously been conducted in idiopathic normal pressure hydrocephalus (iNPH).