Abstract
The Attentional Repulsion Effect (ARE) is a bias attributed to a covert shift of attention towards a peripheral cue, which in turn repulses the perceived position of a target stimulus presented outside the focus of attention (Suzuki & Cavanagh, 1997). The bias is typically examined through a two-alternative forced choice task (2AFC), measuring the capacity of the cue to repel the target across the vertical meridian. To investigate the robustness of the ARE, we compared the classic 2AFC task to a condition in which participants were asked to indicate the absolute perceived location of the target by a computer mouse click. While the two response conditions revealed an ARE of similar magnitude, the computer mouse responses additionally exposed an increased repulsion the further away the target was presented from the cue. This increase, however, declined at a maximum cue-target distance of 4 degrees of visual angle. Covert shifts of visual attention have previously been related to microsacades, miniature fixational eye movements. Therefore, we also tested whether the directional distribution of microsaccades might contribute to the ARE. Microsaccadic responses to cue onset displayed typical dynamics with an initial inhibition followed by a rebound interval (as described in Engbert & Kliegl, 2003). More interestingly, the direction of microsaccades in the cue-target interval was biased towards the cue. These microsaccades support the idea that the ARE may reflect a small shift in the spatial frame of reference: A covert attentional shift towards the cue leads to a presumably unrecognized change in the spatial reference point around fixation (and sometimes in gaze, i.e., a microsaccade). Although target positions are assessed by the visual system in relation to this biased spatial reference point, subsequent responses are given in comparison to the initial point of fixation. These distortions then induce a repulsed spatial representation of the target.
Meeting abstract presented at VSS 2018