Perceptual Grouping without Awareness: Superiority of Kanizsa Triangle in Breaking Interocular Suppression

Abstract

Much information could be processed unconsciously. However, there is no direct evidence on whether perceptual grouping could occur without awareness. To answer this question, we investigated whether a Kanizsa triangle (an example of perceptual grouping) is processed differently from stimuli with the same local components but are ungrouped or weakly grouped. Specifically, using a suppression time paradigm we tested whether a Kanizsa triangle would emerge from interocular continuous flash suppression sooner than control stimuli. Results show a significant advantage of the Kanizsa triangle: the Kanizsa triangle emerged from suppression noise significantly faster than the control stimulus with the local Pacmen randomly rotated (t(9) = −2.78, p = 0.02); and also faster than the control stimulus with all Pacmen rotated 180° (t(11) = −3.20, p<0.01). Additional results demonstrated that the advantage of the grouped Kanizsa triangle could not be accounted for by the faster detection speed at the conscious level for the Kanizsa figures on a dynamic noise background. Our results indicate that certain properties supporting perceptual grouping could be processed in the absence of awareness.

No evidence for surface organization in Kanizsa configurations during continuous flash suppression

“…In a more recent study, however, Wang, Weng, and He (2012) used a variant of the CFS (the breaking-CFS or b-CFS) paradigm to measure how long it took for configurations of standard pacmen (that are able to induce a surface percept when fully visible) to overcome suppression induced by CFS. In apparent contrast with the previous studies, Wang et al (2012) observed that configurations able to induce a triangular Kanizsa surface break suppression faster than non-surfaceinducing control conditions (even when controlling for mirror symmetry in the control stimulus). Wang et al (2012) suggested that this result provided evidence that the processes involved in constructing the Kanizsa surface are able to manifest even when suppressed from awareness using CFS.…”

“…In apparent contrast with the previous studies, Wang et al (2012) observed that configurations able to induce a triangular Kanizsa surface break suppression faster than non-surfaceinducing control conditions (even when controlling for mirror symmetry in the control stimulus). Wang et al (2012) suggested that this result provided evidence that the processes involved in constructing the Kanizsa surface are able to manifest even when suppressed from awareness using CFS. 1 This result would further suggest that some forms of figure-ground assignment might be possible in the absence of perceptual awareness, even while little visual input is able to reach higher areas of the ventral stream thought to mediate these processes.…”

“…While Sobel and Blake (2003) and Harris, Schwarzkopf, Song, Bahrami, and Rees (2011) failed to find evidence for this, Wang, Weng, and He (2012) showed that standard configurations of Kanizsa pacmen would break interocular suppression faster than their rotated counterparts. In the current study, we replicated the findings by Wang et al (2012) but show that neither an account based on the construction of a surface nor one based on the long-range collinearities in the standard Kanizsa configuration stimulus could fully explain the difference in breakthrough times. We discuss these findings in the context of differences in the amplitudes of the Fourier orientation spectra for all stimulus types.…”

“…1A,third column). If the suppression time difference observed in Wang et al (2012) was due to the alignment of the edges rather than the construction of a surface (and engagement of figureground assignment), then the suppression time difference for a standard (aligned) and rotated (non-aligned) cross stimulus should be predicted to be similar to the one seen for the traditional Kanizsa stimulus. A second control stimulus was developed based on the stimuli used by Stanley and Rubin (2003), in which a surface percept is evoked by curved pacmen.…”

“…Given the potential importance of this result, we first set out to replicate the result by Wang et al (2012) using the b-CFS paradigm. We then tested two different sets of control stimuli to disentangle the contribution of the alignment of the edges in the image and the potential to perceive a surface induced by different variants of the Kanizsa configuration.…”