Nonconscious influences from emotional faces: a comparison of visual crowding, masking, and continuous flash suppression

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.

Keywords: CFS; GCC; consciousness; crowding; emotion; face processing; masking.

Figure 1

Left panel: schematic description of the GCC procedure (Experiment 1). Each trial began with the presentation of a fixation cross, followed by a peripheral emotional face surrounded by flankers. This was followed by either a Chinese pictograph on which participants had to make an evaluative judgment (Preference Task), or by a question concerning the emotion expressed by the prime, on which participants had to answer by yes or no (Visibility Task). Experiment 1: peripheral happy or angry faces were presented statically for 2500 ms, surrounded by flankers that were either patterns or neutral faces. Experiment 2: peripheral happy, neutral, or angry faces were presented statically or dynamically for 1200 ms, surrounded by pattern flankers. Experiment 3: happy, neutral, or angry faces were presented foveally for 75 or 2500 ms, surrounded by pattern flankers. Right panel: schematic description of the gaze-contingent substitution. As long as participants’ gaze was maintained in a 5° × 5° region surrounding the fixation cross (“correct gaze”), the peripheral emotional face was presented among the flankers. As soon as participants’ gaze diverged from this region, the emotional face was replaced by the same face with a neutral expression (“gaze-contingent substitution”). In Experiment 2, which contained a neutral baseline condition, the substitution took place with the same face with a different neutral expression.

Figure 2

Comparative results of preference judgment in GCC (Experiment 1). Averaged percentage of pleasant response on the Chinese pictograph, depending on the emotion expressed by angry (dark gray) or happy faces (light gray), when surrounded by pattern flankers or neutral face flankers. Error bars denote one SE.

Figure 3

Comparative results of preference judgment in GCC (Experiment 2). Averaged percentage of pleasant response on the Chinese pictograph, depending on the emotion expressed by angry (dark gray), neutral (gray), or happy faces (light gray). Error bars denote 1 SE. *Denotes a p-value < 0.05.

Figure 4

Comparative results of conscious preference judgment bias (Experiment 3). Averaged percentage of pleasant response on the Chinese pictograph, depending on the emotion expressed by angry (dark gray), neutral (gray), or happy faces (light gray). Short stimulus duration and long stimulus duration conditions are averaged. Error bars denote 1 SE. *Denotes a p-value < 0.05.

Figure 5

Schematic description of the masking procedure (Experiment 4a). Each trial began with the presentation of a fixation cross, followed immediately by a forward mask pattern, and then by the emotional face accompanied by the backward mask pattern. This was followed by a Chinese pictograph (Preference Task), or a question concerning the emotion expressed by the face (Visibility Task). Experiment 4b employed the same procedure, except that the preference task was replaced by a perceptual priming task, in which the target was a face which was either identical or expressing the same emotion as the masked face.

Figure 6

Schematic description of the CFS procedure (Experiment 5a). Each trial began with the presentation of a fixation cross, followed by a dynamic stream of alternating patterns (Mondrian) presented to one eye, while a static emotional face was presented to the other (suppressed eye). When the Mondrian stream stopped, either a Chinese pictograph (Preference Task) or a question concerning the emotion expressed by the face (Visibility Task) was presented to the suppressed eye. In Experiment 5b, except that the preference task was replaced by a perceptual priming task, in which the target was either an identical face expressing the same emotion as the suppressed face or a different face expressing the same emotion. Experiment 5c was identical to Experiment 5a, yet with dynamic faces.

Figure 7

Comparative results of preference judgment bias (Experiments 1, 2, 3, 4a, and 5a,c). Averaged percentage of preference bias from the comparison of angry vs. neutral faces (dark gray, Experiments 2 and 3), happy vs. neutral faces (light gray, Experiments 2 and 3), and happy vs. angry faces (white, Experiments 1, 4a, and 5a,c). GCC stands for gaze-contingent crowding. CFS stands for continuous flash suppression. Horizontal bars denote interactions between negative preference bias in Experiment 2 and 3, and interactions between positive preference bias in Experiments 1, 2, and 4a, 5a,c (see meta-analyses in the discussion). Error bars denote 1 SE. *Denotes a p-value < 0.05, **p-value < 0.01.