Abstract
Binocular rivalry typically is discussed in terms of competition between the eyes. However, pattern coherency also has been suggested to drive rivalry. Whereas different patterns are presented to each eye in the classic rivalry paradigm, Kovacs and colleagues (1996) tested the pattern coherency hypothesis using patchworks of two patterns in which complementary pattern sections were presented to each eye. Reports of coherent pattern ("exclusive") percepts during this patchwork condition, which require interocular grouping, have been cited as evidence for stimulus-based rivalry. Here, we examine aging effects on interocular grouping, and thus stimulus-based rivalry. In each of two experiments, we presented two distinct patterns (concentric rings and diagonal lines) in intermixed trials of the classic and patchwork rivalry paradigms. On each trial, the contrast of the two patterns was either equal or differed significantly (0.6). During classic trials, each eye was shown the same pattern throughout Experiment 1; Experiment 2 counter-balanced the pattern shown to each eye. Eight younger (aged 20-28) and eight older (aged 71-77) observers participated in Experiment 1, and a different set of eight younger (aged 19-26) and eight older (aged 72-77) observers participated in Experiment 2. For the duration of each trial (Experiment 1: 40 s; Experiment 2: 30 s), participants used a handheld button box to classify percepts into three categories: two exclusive (rings or lines) or mixed. Overall, exclusive percepts were reported a significantly greater proportion of time during the classic than patchwork trials. Introducing a difference between the contrast levels of the two patterns increased the monocular and pattern dominance respectively for classic and patchwork trials. Interestingly, there was little evidence of significant age-related changes in the proportion of exclusive percepts or dominance in either paradigm, unlike previous findings for the classic paradigm using less complex stimuli (Beers et al., VSS 2013, 2014).
Meeting abstract presented at VSS 2017