Probing the mechanisms of probe-mediated binocular rivalry

Binocular rivalry occurs when incompatible images are presented simultaneously but separately to each eye. Perceptual dominance reverses over time such that one image temporarily dominates perception, while the other image is suppressed. Prior research has shown that briefly-presented probes modulate perception such that probes presented to the suppressed eye tend to produce shorter percept durations relative to when probes are presented to the dominant eye. This pattern suggests that probes strengthen the competitive strength of the image over which they appear. However, it remains unclear whether probe-modulated effects on binocular rivalry are equivalent across the visual field, in particular as a function of whether probes appear within the region of interocular conflict (i.e on-object) or outside the region of interocular conflict (i.e. off-object). We tested this by manipulating whether probes appeared on-object or off-object. We replicate prior work showing that suppressed-eye probes produce shorter percept durations relative to dominant-eye probes. Critically, however, we show that percept duration also varies as a function of whether probes appear on vs. off the rivalry objects; that is, differences in percept duration between suppressed-eye and dominant-eye probes were much larger for on-object than off-object probes. Importantly, however, the difference between suppressed-eye and dominant-eye probes was still significant for off-object probes. Together these results suggest dynamic mechanisms at work in probe-mediated rivalry, such that on-object probe effects are larger relative to smaller, yet reliable off-object effects.