Abstract
When we attend to a certain visual feature, such as a specific orientation (Tombu & Tsotsos, 2008) or specific colour (Störmer & Alvarez, 2014), processing of features nearby in that space are suppressed (i.e., feature-based surround suppression). In the present study, we investigated feature-based surround suppression in a new feature domain, motion direction, using motion repulsion as a measurement. Chen and colleagues (2005) suggested that attention to one motion direction reduces motion repulsion by inhibiting the other direction. Based on this finding, we conducted a similar direction judgment task having naïve participants. They reported perceived directions of two superimposed motions after viewing the motions for 2 sec. The directional differences between two motions systematically varied (10~70 deg) and the surfaces were separated by different colours (green or red). In the unattended condition, participants performed direction judgment tasks only, attending equally to both motions. In the attended condition, a colour cue was presented, indicating which motion participants should attend. Participants were asked to detect a brief directional shift of the cued motion and then, report the perceived motion directions. We compared the magnitude of motion repulsion between the two attention conditions. In contrast to the findings of Chen and colleagues, participants showed greater motion repulsion in the attended condition than in the unattended condition, especially when two motions moved along nearby directions. The results suggest that feature-based surround suppression exists in the motion domain and that it may occur on an early stage of motion processing where the global direction of motion is computed.
Meeting abstract presented at VSS 2017