Nonconscious Influences from Emotional Faces: A Comparison of Visual Crowding, Masking, and Continuous Flash Suppression

Nathan Faivre,Vincent Berthet,Sid Kouider

doi:10.3389/fpsyg.2012.00129

Abstract

In the study of nonconscious processing, different methods have been used in order to render stimuli invisible. While their properties are well described, the level at which they disrupt nonconscious processing remains unclear. Yet, such accurate estimation of the depth of nonconscious processes is crucial for a clear differentiation between conscious and nonconscious cognition. Here, we compared the processing of facial expressions rendered invisible through gaze-contingent crowding (GCC), masking, and continuous flash suppression (CFS), three techniques relying on different properties of the visual system. We found that both pictures and videos of happy faces suppressed from awareness by GCC were processed such as to bias subsequent preference judgments. The same stimuli manipulated with visual masking and CFS did not bias significantly preference judgments, although they were processed such as to elicit perceptual priming. A significant difference in preference bias was found between GCC and CFS, but not between GCC and masking. These results provide new insights regarding the nonconscious impact of emotional features, and highlight the need for rigorous comparisons between the different methods employed to prevent perceptual awareness.

Highlights

Over the past 20 years, it has been clearly established that stimuli that are inaccessible to conscious reports can still induce behavioral and neural responses (Marcel, 1983; Kouider and Dehaene, 2007)
The visibility task confirmed that backward masking prevented conscious access to the facial expressions, as performance was at chance for both Experiment 4a (mean d = −0.05; t (18) = −0.67; SD = 0.3, p > 0.5) and Experiment 4b (mean d = 0.11; t (10) = 0.32; SD = 1.15, p > 0.7)
FACE PERCEPTION UNDER VISUAL CROWDING In a series of eight experiments, we characterized face processing outside perceptual awareness using three different techniques: gaze-contingent crowding (GCC), visual masking, and continuous flash suppression (CFS)

Summary

Introduction

Over the past 20 years, it has been clearly established that stimuli that are inaccessible to conscious reports can still induce behavioral and neural responses (Marcel, 1983; Kouider and Dehaene, 2007). As nonconscious influences are usually of small amplitude, their measurement requires a sensory stimulation of maximum possible energy satisfying the criterion of invisibility. To ensure specificity, they must be associated with a strict control of stimulus visibility to avoid potential confounds with conscious influences. In order to prevent conscious processing, researchers have relied often on two kinds of manipulations, namely visual masking and continuous flash suppression (CFS; see Kim and Blake, 2005, for other techniques relying notably on attentional manipulations). In CFS, a stimulus of interest, is presented to one eye while a dynamic stream of salient patterns is presented to the other eye. The stimulus is suppressed and remains undetectable even after exposure of several seconds (Tsuchiya and Koch, 2005)

Methods

Results

Conclusion