Abstract
The perception of depth depends on the calculation of a binocular cross-correlation by cortical neurons. The binocular energy model of neural responses predicts depth might be perceived in the reversed direction when the contrast of dots presented to one eye is reversed. Presenting an anti-correlated random-dot stereogram target (aRDS) adjacent to a correlated random-dot stereogram background (cRDS) has produced reversed depth, however these results are inconsistent (Hibbard et al., 2014). Aoki et al., (2017) found robust perception of reversed depth when there was a non-zero absolute disparity for the surrounding cRDS, and a zero disparity aRDS. They suggest that the mixed findings across studies may be accounted for by the presence of a spatial gap between the target and surround. Alternatively, the perception of reversed depth may be a result of the overlap of background and foreground features around the vertical edges of the stimuli, rather than the absence of a gap. To test this, we assessed whether (1) the gap size (0, 10 or 20 arc min) (2) the correlation of dots (aRDS or cRDS) or (3) the border orientation ( circular target, or horizontal or vertical edge) affected the perception of depth. For a minority of observers, reversed depth was seen in aRDS for the circular target when no gap was present, and this effect reduced as the gap size increased. However, when scores were averaged across observers, performance on aRDS stimuli was at chance. Depth was mostly perceived in the correct direction for aRDS edge stimuli, with the effect increasing with the gap size. The inconsistency across conditions suggest a complex interaction between first- and second-order depth detection mechanisms and the range of spatial frequency tuning. The separation between target and surround does not appear to exclusively account for the perception of reversed depth in aRDS stimuli.
Meeting abstract presented at VSS 2018