On the use of continuous flash suppression for the study of visual processing outside of awareness.

Eunice Yang,Jan Brascamp,Randolph Blake,Min-Suk Kang

doi:10.3389/fpsyg.2014.00724

Abstract

The interocular suppression technique termed continuous flash suppression (CFS) has become an immensely popular tool for investigating visual processing outside of awareness. The emerging picture from studies using CFS is that extensive processing of a visual stimulus, including its semantic and affective content, occurs despite suppression from awareness of that stimulus by CFS. However, the current implementation of CFS in many studies examining processing outside of awareness has several drawbacks that may be improved upon for future studies using CFS. In this paper, we address some of those shortcomings, particularly ones that affect the assessment of unawareness during CFS, and ones to do with the use of “visible” conditions that are often included as a comparison to a CFS condition. We also discuss potential biases in stimulus processing as a result of spatial attention and feature-selective suppression. We suggest practical guidelines that minimize the effects of those limitations in using CFS to study visual processing outside of awareness.

Highlights

During our waking hours our eyes provide us with more sensory information than we can possibly process in detail, and only a small proportion of this information reaches awareness
One version that has recently become popular as a means for erasing visual stimuli from awareness is called continuous flash suppression (CFS; Tsuchiya and Koch, 2005), and it is the focus of our paper
Considering that visible or weakly suppressed features may still occur, one further measure one can take is to use large stimulus sets or to replicate findings with multiple stimulus sets, to minimize learned associations or effects of stimulus repetition across trials. Those of us interested in visual processing outside of awareness have at our disposal an impressive array of tools for manipulating visual awareness

Summary

Introduction

During our waking hours our eyes provide us with more sensory information than we can possibly process in detail, and only a small proportion of this information reaches awareness. At the same time, psychophysical techniques for rendering stimuli perceptually invisible continue to be developed, providing researchers with an ever more varied array of experimental tools for investigating processing outside of awareness (review by Kim and Blake, 2005). Some of these tools exploit the reflexive suppression that occurs when different images are simultaneously presented to the two eyes, i.e., dichoptic stimulation. An advantage of dichoptic stimulation techniques over other approaches is that an observer can monocularly view one of any variety of salient stimuli, yet remain unaware of its presence for seconds at a time. One version that has recently become popular as a means for erasing visual stimuli from awareness is called continuous flash suppression (CFS; Tsuchiya and Koch, 2005), and it is the focus of our paper

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