Amodal completion is modulated by lightness similarity

Abstract

The strength of amodal completion is known to be modulated by contour relationships and global shape. Some researchers have shown that amodal completion also depends on surface similarity, but they have not distinguished the relative importance of similarity in surface representations either pre or post lightness constancy. In the experiments reported here, we aimed to determine whether amodal completion depends on processes that occur either before or after the establishment of lightness constancy. We used computer rendering techniques to vary the consistency of a cast shadow with a decrement in luminance on one side of a partially occluded surface. We found that perceived completion depended on the consistency of the decrement in surface luminance with the orientation of a cast shadow (Exp. 1). In Experiment 2, we generated occluded surface fragments that could be either luminance-matched or lightness-matched to surface fragments on the opposite side of the occluder, and we found that the strength of amodal completion depended primarily on similarity in the perceived surface reflectance. In Experiments 3 and 4, we performed apparent-motion tasks to obtain converging evidence for grouping on the basis of perceived similarity in lightness. We found that matching surfaces in lightness significantly improved the apparent motion of surfaces behind an occluder, as compared with surfaces that were matched in contrast alone. These results suggest that amodal completion depends on the perceived similarity in lightness of partially occluded surface fragments.

Investigating local and global effects of surface colours and contours in amodal completion

“…These basic findings already show that amodal completion can be influenced by the visible colours in the occlusion pattern. In addition, these results are consistent with previous findings that surface characteristics, more specifically colour, play a role in amodal completion (Dadam et al, 2012;Kim et al, 2014;Pinna, 2008;Su et al, 2010;Yin et al, 1997). Next, we proposed an analysis in which we had a closer look at the net effect of colour context, i.e., the colour context analyses.…”

“…Using displays with illusory colours, Pinna (2008) showed that amodal completion could also be modulated by perceived colours and that they could even prevent completion to occur (which happened when the perceived colours suggested a hole instead of an occluder). More recently, Kim, Jeng, and Anderson (2014) studied the influence of lightness similarity, showing modulating effects of perceived surface similarities, e.g., after accounting for the effect of shadows on the visible contour fragments. A study that explicitly focused on the perceived surface characteristics behind the occluder was performed by Yin, Kellman, and Shipley (1997) who constructed stimuli to isolate surface colour completion from boundary completion.…”

Amodal completion across the brain: The impact of structure and knowledge

“…In conflict with these two stimulus-driven accounts, amodal completion seems not solely influenced by low-level stimulus configurations but also impacted by various high-level contextual cues, as demonstrated in several studies. These cues encompass factors such as lighting conditions ( Kim, Jeng, & Anderson, 2014 ), spatial context ( Rauschenberger, Peterson, Mosca, & Bruno, 2004 ), temporal context ( Plomp & van Leeuwen, 2006 ), task demands ( Lee & Vecera, 2005 ), and familiarity with material properties ( Gerbino & Zabai, 2003 ; Vrins, de Wit, & van Lier, 2009 ) and object shapes ( Hazenberg & van Lier, 2016 ; Yun, Hazenberg, & van Lier, 2018 ). Moreover, research has shown that explicit learning can influence the preferred completion for occlusion patterns, especially in cases where local and global cues conflict ( Hazenberg, Jongsma, Koning, & van Lier, 2014 ).…”

Measuring the perceptual grouping of non-adjacent surfaces that are invisibly (amodally) or visibly connected

“…The visual system’s incorporation of such hidden visual information into its 3-dimensional representation of the objects in a scene is called amodal completion [1]. Previous studies have been concerned with the stimulus conditions necessary for amodal completion, including good continuation [2], luminance similarity [3], and shape similarity [4]. Other researchers have shown that amodal completion can be affected by top-down influences entailing knowledge of the partially occluded objects [5,6].…”