Grasp cueing and joint attention

"Be careful what you do": How social threat influences social attention driven by reach-to-grasp movements

Social attention is the ability to share with social partners the attentional focus on an object and to orient attentional resources after observing others' behaviors. In the present work, we analyzed whether social threat may influence social attention during the observation of social agents' reach-to-grasp movements. In two experimental studies, we adopted a Posner-like paradigm: participants were required to classify neutral stimuli appearing in a congruent or incongruent position with the actor's movement. Membership (ingroup vs. outgroup) and contextual cues (neutral vs. threatening objects) were manipulated. The results showed a robust action-cueing effect: responses to stimuli in a congruent position with the actor's action were faster than responses to incongruent stimuli. Interestingly, we found a stronger effect for the threatening outgroup (i.e., Iraqi) than for the ingroup (i.e., Italian), especially in presence of menacing objects. No effects were found when observing the non-threatening outgroup (i.e., Japanese).

Coordinating attention requires coordinated senses

From playing basketball to ordering at a food counter, we frequently and effortlessly coordinate our attention with others towards a common focus: we look at the ball, or point at a piece of cake. This non-verbal coordination of attention plays a fundamental role in our social lives: it ensures that we refer to the same object, develop a shared language, understand each other's mental states, and coordinate our actions. Models of joint attention generally attribute this accomplishment to gaze coordination. But are visual attentional mechanisms sufficient to achieve joint attention, in all cases? Besides cases where visual information is missing, we show how combining it with other senses can be helpful, and even necessary to certain uses of joint attention. We explain the two ways in which non-visual cues contribute to joint attention: either as enhancers, when they complement gaze and pointing gestures in order to coordinate joint attention on visible objects, or as modality pointers, when joint attention needs to be shifted away from the whole object to one of its properties, say weight or texture. This multisensory approach to joint attention has important implications for social robotics, clinical diagnostics, pedagogy and theoretical debates on the construction of a shared world.

[Observing grasping action from egocentric perspective modulates observer's visual attention]

Previous studies demonstrated that observing another person's grasp action modulated the observer's attention to the object in a manner congruent with another person's action goal. These studies suggest that this grasp-cueing effect results from representation of the observer's understanding of action intention in the mirror neuron system. This system serves as the neural mechanism underlying action-oriented goals, regardless of whether they are those of the observer or others. The present study examined whether the grasp-cueing effect emerged even when a grasp action was observed from an egocentric (observer's own) perspective. Reaction times were faster when the target was presented over the object that was congruent with the action goal implied by the size of the hand aperture. This indicated that the grasp cueing effect occurred when the stimulus was observed from an egocentric perspective, consistent with the view that this effect resulted from the observer's understanding of action intention as represented in the mirror neuron system.

Random walks on the mental number line

The direction of influence between conceptual and motor activation, and its relevance for real-life activities, is still unclear. Here, we use the frequently reported association between small/large numbers and left/right space to investigate this issue during walking. We asked healthy adults to generate random numbers as they made lateral turns and found that (1) lateral turn decisions are predicted by the last few numbers generated prior to turning; (2) the intention to turn left/right makes small/large numbers more accessible; and (3) magnitude but not order of auditorily presented numbers influences the listener's turn selection. Our findings document a bidirectional influence between conceptual and motor activation and point to a hierarchically organized conceptual-motor activation.

Grasping the other's attention: the role of animacy in action cueing of joint attention

The current experiment investigates the role of animacy on grasp-cueing effects as investigated in joint attention research. In a simple detection task participants responded to the colour change of one of two objects of identical size. Before the target onset, we presented a cueing stimulus consisting of either two human hands with a small and a large grip aperture (animate condition) or two comparable U-shaped figures with small and large aperture (inanimate condition). Depending on the size of the objects and the arrangement of the apertures (i.e., large aperture to the left and small aperture to the right or vice versa), either the left or right object matched the grasping hand or U-shapes. Our data show that biological grasping actions modulate the observer's attention whereas the perception of inanimate stimuli does not result in a comparable cueing effect. This strong impact of animacy on attentional priming suggests that grasp cueing represents a marker of a joint attention mechanism that involves spontaneous simulation of the observed motor behaviour.