Unconscious perception: A model-based approach to method and evidence

Abstract

Unconscious perceptual effects remain controversial because it is hard to rule out alternative conscious perception explanations for them. We present a novel methodological framework, stressing the centrality of specifying the single-process conscious perception model (i.e., the null hypothesis). Various considerations, including those of SDT (Macmillan & Creelman, 1991), suggest that conscious perception functions hierarchically, in such a way that higher level effects (e.g., semantic priming) should not be possible without lower level discrimination (i.e., detection and identification). Relatedly, alternative conscious perception accounts (as well as the exhaustiveness, null sensitivity, and exclusiveness problems- Reingold & Merikle, 1988) predict positive relationships between direct and indirect measures. Contrariwise, our review suggests that negative and/or nonmonotonic relationships are found, providing strong evidence for unconscious perception and further suggesting that conscious and unconscious perceptual influences are functionally exclusive (cf. Jones, 1987), in such a way that the former typically override the latter when both are present. Consequently, unconscious perceptual effects manifest reliably only when conscious perception is completely absent, which occurs at the objective detection (but not identification) threshold.

A task-difficulty artifact in subliminal priming

“…Moreover, perhaps subliminal priming will appear at even lower prime durations than the 8 msec that was used here (see Snodgrass et al, 2004, for an alternative that anticipates such a result). Rather, our results in number priming serve as a general warning that any findings with the two-task paradigm are tenuous.…”

“…In the last decade, however, the field has seemingly reversed the Cheesman and Merikle (1984) finding, and many researchers claim to have demonstrated the most impressive form of subliminal priming-namely, that there are priming effects even for stimuli that cannot, under any circumstance, be detected or classified (see, e.g., Dehaene et al, 1998;Greenwald, Draine, & Abrams, 1996;Kunde, Kiesel, & Hoffmann, 2003;Van Opstal, Reynvoet, & Verguts, 2005; see Snodgrass, Bernat, & Shevrin, 2004, for a review). These findings of subliminal priming not only were surprising in their own right, but also influenced theories of human information processing (see, e.g., Greenwald, Abrams, , emotional processing (see, e.g., Li, Zinbarg, Boehm, & Paller, 2008), and mental pathology (see, e.g., Dehaene et al, 2003).…”

Neural Dissociation between Visual Awareness and Spatial Attention

“…Traditionally, subjective and objective criteria have been used based on introspective reports and forced-choice decisions, respectively (Merikle et al, 2001;Snodgrass et al, 2004). Here we confronted the two approaches to assess subjects' awareness of the faint stimuli: we used a subjective criterion based on subjects' reports of their visual experience (detection task) along with an objective criterion based on subjects' ability to identify the stimulus (forced-choice orientation discrimination task).…”

Valid distinctions between conscious and unconscious perception?

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In this commentary, we discuss the strengths and limitations of Snodgrass, Bernat, and Shevrin's (2004)

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“…In this commentary, we discuss the strengths and limitations of Snodgrass, Bernat, and Shevrin's (2004) Snodgrass, Bernat, and Shevrin (2004) propose a novel and provocative approach to the valid measurement and demonstration of unconscious perception. In this commentary, we consider the strengths and weaknesses of this approach, followed by suggestions for further research.…”