The spatial alignment effect in near and far space: a kinematic study.

The present experiment aimed at verifying whether the spatial alignment effect modifies kinematic parameters of pantomimed reaching-grasping of cups located at reachable and not reachable distance. The cup's handle could be oriented either to the right or to the left, thus inducing a grasp movement that could be either congruent or incongruent with the pantomime. The incongruence/congruence induced an increase/decrease in maximal finger aperture, which was observed when the cup was located near but not far from the body. This effect probably depended on influence of the size of the cup body on pantomime control when, in the incongruent condition, cup body was closer to the grasp hand as compared to the handle. Cup distance (near and far) influenced the pantomime even if it was actually executed in the same peripersonal space. Specifically, arm and hand temporal parameters were affected by actual cup distance as well as movement amplitudes. The results indicate that, when executing a reach-to-grasp pantomime, affordance related to the use of the object was instantiated (and in particular the spatial alignment effect became effective), but only when the object could be actually reached. Cup distance (extrinsic object property) influenced affordance, independently of the possibility to actually reach the target.

The eye contact effect in request and emblematic hand gestures.

Request and emblematic gestures, despite being both communicative gestures, do differ in terms of social valence. Indeed, only the former are used to initiate/maintain/terminate an actual interaction. If such a difference is at stake, a relevant social cue, i.e. eye contact, should have different impacts on the neuronal underpinnings of the two types of gesture. We measured blood oxygen level-dependent signals, using functional magnetic resonance imaging, while participants watched videos of an actor, either blindfolded or not, performing emblems, request gestures, or meaningless control movements. A left-lateralized network was more activated by both types of communicative gestures than by meaningless movements, regardless of the accessibility of the actor's eyes. Strikingly, when eye contact was taken into account as a factor, a right-lateralized network was more strongly activated by emblematic gestures performed by the non-blindfolded actor than by those performed by the blindfolded actor. Such modulation possibly reflects the integration of information conveyed by the eyes with the representation of emblems. Conversely, a wider right-lateralized network was more strongly activated by request gestures performed by the blindfolded than by those performed by the non-blindfolded actor. This probably reflects the effect of the conflict between the observed action and its associated contextual information, in which relevant social cues are missing.

Sensory-motor interference abolishes repetition priming for observed actions, but not for action-related verbs.

Several studies on humans have shown a recruitment of the sensory-motor system in the perception of action-related visual and verbal material, suggesting that actions are represented through sensory-motor processes. To date, these studies have not disentangled whether such a recruitment is epiphenomenal or necessary to action representation. Here we took advantage of repetition priming as a tool to investigate the cognitive representation of actions, and systematically looked whether a concurrent motor or verbal task had a detrimental effect on this representation. In a first experiment participants discriminated images depicting meaningless and meaningful actions, while performing either a concurrent sensory-motor or an articulatory suppression task. Images were classified as depicting a repeated or a new action, relative to the previous image in the trial series. We found a facilitation by repetition priming, that was unaffected by the articulatory task but was completely abolished by the sensory-motor task. In a second experiment, we investigated whether the sensory-motor system is also causally involved in processing action-related verbs. In this experiment actions were presented as written infinitive verbs rather than as images. The facilitation by repetition priming was again unaffected by the concurrent articulatory task, while the sensory-motor concurrent task, although reducing the facilitation, did not abolish it. Our data provide evidence that the sensory-motor system is differentially involved during visual processing of actions and during processing of action-related verbs. Results are discussed within the theoretical frame of embodied cognition.