Abstract
A recent focus in the field of consciousness research involves investigating the propensity of initially non-conscious visual information to gain access to consciousness. A critical tool for measuring conscious access is the so-called breaking continuous flash suppression paradigm (b-CFS). In this paradigm, a high contrast dynamic pattern is presented to one eye, thereby temporarily suppressing a target stimulus that is presented to the other eye. The time it takes for observers to report (e.g., the location of) the initially suppressed stimulus provides a measure of conscious access. Typical observations in b-CFS studies include the finding that upright faces are released from suppression faster than inverted faces, and the finding that stimuli that match the current content of visual working memory are released from suppression faster than mismatching stimuli. Interestingly, the extent to which observers exhibit these effects varies extensively (in the range of hundreds of milliseconds). By re-analyzing existing datasets and a new dataset we establish that the difference in RTs between conditions in b-CFS tasks (i.e., the effect of interest) is highly correlated with participants' overall suppression durations, and with their trial-to-trial variability in RTs. We advocate the usage of a simple latency- normalization method, which (1) removes the between-subject variability in suppression duration from the effect of interest, while (2) providing distributions of RT differences that are better suited for parametric testing. We next compare this latency-normalization method to two other transformations that are widely applied on within-subject RT data (z-transformations and log-transformations). Finally, we tentatively discuss how trial-to-trial variability and overall suppression duration might relate to prolonged phases of shallow suppression that are more prone to modulations of conscious access.
Highlights
Consciousness researchers have many psychophysical tools at their disposal to render visual input invisible to the observer
We advocate caution in considering this interpretation, as it might be a spurious correlation emerging from the correlation between overall RTs and RT variability (e.g., Wagenmakers and Brown, 2007), which we find in the Face Experiment, R = 0.797, p < 0.001, BF10 = 4∗1023, in the Color Experiment, R = 0.736, p < 0.001, BF10 = 4∗104, and in the Shape Experiment, R = 0.659, p = 0.002, BF10 = 23
Using three representative breaking continuous flash suppression paradigm (b-Continuous flash suppression (CFS)) datasets, we established that longer RTs relate to larger RTs differences between experimental conditions in the b-CFS paradigm
Summary
Consciousness researchers have many psychophysical tools at their disposal to render visual input invisible to the observer (for reviews, see Kim and Blake, 2005; Breitmeyer, 2015; Overgaard, 2015). One method in particular has been increasingly dominant in the recent consciousness literature. Many studies use the time it takes for an initially suppressed target stimulus to overcome CFS as a measure of conscious access. This method is referred to as “breaking continuous flash suppression” (b-CFS; Jiang et al, 2007; Stein et al, 2011a; for a review, see Gayet et al, 2014)
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