Seeing the invisible: The scope and limits of unconscious processing in binocular rivalry

Abstract

When an image is presented to one eye and a very different image is presented to the corresponding location of the other eye, they compete for perceptual dominance, such that only one image is visible at a time while the other is suppressed. Called binocular rivalry, this phenomenon and its deviants have been extensively exploited to study the mechanism and neural correlates of consciousness. In this paper, we propose a framework, the unconscious binding hypothesis, to distinguish unconscious and conscious processing. According to this framework, the unconscious mind not only encodes individual features but also temporally binds distributed features to give rise to cortical representation, but unlike conscious binding, such unconscious binding is fragile. Under this framework, we review evidence from psychophysical and neuroimaging studies, which suggests that: (1) for invisible low level features, prolonged exposure to visual pattern and simple translational motion can alter the appearance of subsequent visible features (i.e. adaptation); for invisible high level features, although complex spiral motion cannot produce adaptation, nor can objects/words enhance subsequent processing of related stimuli (i.e. priming), images of objects such as tools can nevertheless activate the dorsal pathway; and (2) although invisible central cues cannot orient attention, invisible erotic pictures in the periphery can nevertheless guide attention, likely through emotional arousal; reciprocally, the processing of invisible information can be modulated by attention at perceptual and neural levels.

Language can boost otherwise unseen objects into visual awareness

“…This alternative depends on the suppressed image receiving substantial semantic processing. However, existing evidence suggests that CFS (and interocular suppression more broadly) seems to interfere with visual processes occurring before semantic analysis of words (48,49) and objects (50,51); for example, interocularly suppressed words and objects cannot prime subsequent processing of related stimuli (52), and neurons in medial temporal cortex do not respond to images suppressed through CFS in humans (53) or suppressed through binocular rivalry in monkeys (54). *This hit rate is substantially higher than the 50% QUEST threshold to which the staircasing procedure was set because participants' performance tends to improve during the course of the experiment.…”

Melodic sound enhances visual awareness of congruent musical notes, but only if you can read music

“…This conclusion contrasts with other findings showing that contextual congruence (30, 31) and experience-based familiarity (32) can influence how quickly a visual stimulus emerges from interocular suppression to achieve dominance. Hence, we wanted to examine more carefully the impact of INC and CON during phases of score suppression using a discrete trial probe technique that is arguably more sensitive than rivalry tracking when it comes to detecting weak, subliminal influences during rivalry (33,34). This probe technique involves introducing CON or INC auditory melodies unpredictably when the musical score is dominant or suppressed ( Fig.…”

Less Is More: Semantic Information Survives Interocular Suppression When Attention Is Diverted

“…With this form of dissociation, scientists have asked to what extent visual stimuli in the suppression phase are processed in the absence of awareness. It is now well established that basic features (e.g., stimulus orientation and motion direction) are registered without awareness (Wiesenfelder and Blake, 1990;Blake et al, 2006), but it has been intensely debated whether our brain can extract semantic information of invisible words during interocular suppression (Lin and He, 2009;Gayet et al, 2014;Sterzer et al, 2014;Yang et al, 2014).…”