Academic journal article Attention, Perception and Psychophysics

Longer Is Not Better: Nonconscious Overstimulation Reverses Priming Influences under Interocular Suppression

Academic journal article Attention, Perception and Psychophysics

Longer Is Not Better: Nonconscious Overstimulation Reverses Priming Influences under Interocular Suppression

Article excerpt

Published online: 28 October 2011

© Psychonomic Society, Inc. 2011

Abstract Previous research has shown that stimuli rendered invisible through masking can be sufficiently processed to induce nonconscious influences and facilitate subsequent recognition. However, masking paradigms are methodologically restricted such that stimuli cannot be presented for longer than a few tens of milliseconds, potentially restricting the strength of nonconscious influences. By adapting a masked face repetition priming paradigm to a recent interocular suppression method, we investigated whether longer periods of invisible prime stimulation lead to larger nonconscious influences on subsequent recognition. Surprisingly, we found that while brief periods of invisible prime stimulation result in classical facilitation priming, long periods of invisible stimulation lead to negative priming influences, reflecting impairment of subsequent recognition. In contrast, when the prime was visible, longer exposure resulted in classical facilitation effects, revealing qualitative differences between conscious and nonconscious processes. Altogether, the present findings reveal the existence of a nonconscious overstimulation cost, as well as an important dissociation between conscious and nonconscious processing.

Keywords Repetition priming . Interocular suppression . Nonconscious processing . Negative priming

Introduction

To what extent can perceptual information be processed in the absence of awareness? Nowadays, while the existence of nonconscious processing is definitely accepted, the debate has shifted to its extent and limits (Kouider & Dehaene, 2007; Lin & He, 2009). Masked priming experiments, in which a prime stimulus is rendered invisible by the joint use of brief presentations (~50 ms) and backward masking, have been particularly helpful in demonstrating subliminal influences at behavioral and neural levels (Kouider & Dehaene, 2007; Marcel, 1983). In this paradigm, the prime stimulus activates multiple representation levels, but its processing is interrupted by the mask prior to visual awareness. Importantly, this activation by the invisible prime provides a "head start" to the processing of subsequent visible targets, resulting in facilitation priming effects. By varying the relationship (e.g., physical, semantic, etc.) between the prime and the target, one can investigate the depth of nonconscious processing. However, masking has one considerable limitation: It cannot be used to create sustained periods of perceptual invisibility. Indeed, masking is effective only as long as stimulus duration does not exceed a few tens of milliseconds (~50 ms; see, e.g., Gelskov & Kouider, 2010). Past evidence for restricted nonconscious influences might thus reflect methodological limits (i.e., short durations induce weak signals and, thus, weak influences), rather than theoretical constraints on the nature of nonconscious perceptual processes.

To overcome this practical limit, research has focused on alternative methods that offer longer periods of invisible stimulation, such as binocular rivalry (Tong, Meng, & Blake, 2006). Rivalry reflects the fact that when two incompatible stimuli (e.g., a face and a house) are presented to an observer, one in each eye, they compete for perceptual awareness, which, as a result, oscillates between the two possible percepts. When one percept wins the competition, it is totally visible and then fully perceived by the observer, while the other percept is completely suppressed and, hence, rendered invisible for a few seconds. Nevertheless, perceptual switches in rivalry cannot be manipulated reliably (i.e., one cannot control the duration of invisible stimulation). Recently, an extension of rivalry termed continuous flash suppression (CFS) has been reported as a powerful method that can surmount both the limitations of visual masking and rivalry (Fang & He, 2005; Tsuchiya & Koch, 2005). …

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