Abstract
We present a new “gaze-contingent substitution” paradigm, aiming at characterizing unconscious processes in crowded displays. Crowding occurs when nearby flankers impede the identification, but not the detection, of a peripheral stimulus. The origins of crowding effects in the visual system are still only poorly understood. According to bottom-up proposals, hard-wired limitations in the primary visual cortex cause the information about the crowded stimulus to be lost very early, any information being pooled with that of the flankers. According to top-down proposals, however, the smallest region of the visual field that can be isolated by attention is much coarser than the smallest details resolvable by vision. Crowding would then reflect a partial conscious read-out of perceived information due to a lack of attentional resolution. In this work, we show that not only static but also dynamic emotional primes (i.e., videos of faces) rendered unconscious by crowding can bias a decision on subsequent preference judgments. Importantly, control experiments show that this unconscious transfer of valence does not occur with inverted faces. Other methods such as continuous flash suppression, during which stimuli are suppressed from awareness through binocular rivalry, are also studied. Comparison of the two methods reveals stronger unconscious effects in crowding. These results are discussed in light of current theories of crowding and favor a top-down explanation in which crowded stimuli are not lost in V1 but rather can bias decisions at an abstract level. These results motivate continued research on the unconscious processing of dynamic stimuli.