When one sees what the other hears: crossmodal attentional modulation for gazed and non-gazed upon auditory targets.

Three experiments investigated the nature of visuo-auditory crossmodal cueing in a triadic setting: participants had to detect an auditory signal while observing another agent's head facing one of the two laterally positioned auditory sources. Experiment 1 showed that when the agent's eyes were open, sounds originating on the side of the agent's gaze were detected faster than sounds originating on the side of the agent's visible ear; when the agent's eyes were closed this pattern of responses was reversed. Two additional experiments showed that the results were sensitive to whether participants could infer a hearing function on the part of the agent. When no ear was depicted on the agent, only a gaze-side advantage was observed (Experiment 2), but when the agent's ear was covered (Experiment 3), an ear side advantage was observed only when hearing could still be inferred (i.e., wearing the hat) but not when hearing was inferred to be diminished (i.e., wearing a helmet). The findings are discussed in the context of inferential and simulation processes and joint attention mechanisms.

Joint attention: inferring what others perceive (and don't perceive).

Research has shown that observers automatically align their attention with another's gaze direction. The present study investigates whether inferring another's attended location affects the observer's attention in the same way as observing their gaze direction. In two experiments, we used a laterally oriented virtual human head to prime one of two laterally presented targets. Experiment 1 showed that, in contrast to the agent with closed eyes, observing the agent with open eyes facilitated the observer's alignment of attention with the primed target location. Experiment 2, where either sunglasses or occluders concealed the agent's eye direction, showed that only the agent with the sunglasses facilitated the observer's alignment of attention with the target location. Taken together, the data demonstrate that head orientation alone is not sufficient to trigger a shift in the observer's attention, that gaze direction is crucial to this process, and that inferring the region to which another person is attending does facilitate the alignment of attention.

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.