Size Increase in Panum’s Fusional Range Is Driven by Eccentricity and Not Separation

Abstract

Previous research has demonstrated that Panum’s fusional range increases in the periphery, and this increase is usually attributed to eccentricity. However, it is unclear whether the increase in the periphery is driven by eccentricity or separation between the stimulus and the central fixation marker. In Experiment 1, we independently measured the effects of eccentricity and stimulus separation on Panum’s fusional range for horizontal disparities. We observed significant increases in Panum’s range as eccentricity increased independently of stimulus separation. Experiment 2 revealed that the extent of Panum’s fusional range for vertical disparities increased with eccentricity independently of stimulus separation. Taken together, these results strongly support previously held conclusions that Panum’s fusional range for both horizontal and vertical disparities increases with increasing eccentricity and is little impacted by stimulus separation.

Large depth differences between target and flankers can increase crowding: Evidence from a multi-depth plane display

“…Future research should therefore aim to utilize stimuli that better capture the complexity and heterogeneity of natural scenes. Future work should also investigate if the reported effects of depth on crowding in our study hold at different target eccentricities, particularly given that the range of Panum’s Fusional Area changes with eccentricity ( Hampton and Kertesz, 1983 ; Harrold and Grove, 2019 ; Qin et al, 2006 ). Nevertheless, our findings still show that crowding from clutter outside Panum’s Fusional Area has the potential to significantly impact object recognition and visual perception in the peripheral field.…”

“…Outside Panum’s Fusional Area, there is a loss of stereoscopic depth perception and either double vision (diplopia) may be experienced, or single vision may occur if the image from one eye is partly suppressed ( Georgeson and Wallis, 2014 ; Ono et al, 1977 ; Spiegel et al, 2016 ; Stidwill and Fletcher, 2010 ). The spatial extent of Panum’s Fusional Area depends on the spatial frequency of the stimuli ( Maiello et al, 2020 ; Pulliam, 1981 ; Reynaud and Hess, 2017 ; Wilcox and Allison, 2009 ; Yang and Blake, 1991 ) and increases with eccentricity ( Hampton and Kertesz, 1983 ; Harrold and Grove, 2019 ; Qin et al, 2006 ).…”