Abstract
Binocular rivalry is a phenomenon that can be observed when the two eyes receive conflicting information, leading to perceptual alternations between the eyes' images. Evidence suggests, however, that when attention is withdrawn from such dichoptically presented stimuli, these alterations do not continue and the images are, instead, processed equally (Zhang et al., 2011; Brascamp et al., 2011; Eo et al., 2016). This raises the question of how the conflicting images are processed instead. We test the possibility that without attention the conflict is resolved by binocular fusion, so that the conflicting inputs have a combined representation in the cortex (Zhang et al., 2011). We designed an experiment to ensure that two images, when combined during processing, have a measurably different effect than when processed separately, and investigated which effect was obtained when the unattended dichoptic images were presented. Specifically, we made use of the fact that the motion aftereffect (MAE) of two moving gratings, when these are presented superimposed, has a different direction than when they are presented sequentially (Mussap et al., 1998). Our experiment included both such a superimposed condition and such a sequential condition but, critically, also a condition where these two gratings were presented to different eyes without attention. We hypothesized, if such dichoptically presented images are fused without attention, this critical condition should yield an MAE direction that matches that of the superimposed gratings. We found that MAE direction in our critical condition, where we presented stimuli dichoptically while withdrawing attention, was significantly different from that in the superimposed condition but similar to that in the sequential condition. We conclude that, without attention, conflicting information from the two eyes is not fused, at least not at the level where our aftereffects arise.
Meeting abstract presented at VSS 2018