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Steven J. Haase, Gary D. Fisk; Signal Detection Theory as a modeling tool for resolving controversies surrounding unconscious perception. Journal of Vision 2002;2(7):22. doi: 10.1167/2.7.22.
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© 2017 Association for Research in Vision and Ophthalmology.
The concept of unconscious perception has generated continual controversy throughout psychology's history. We propose that much of cognitive psychology rests on mistaken or tacit assumptions that significant, high-level (e.g., semantic) processing occurs outside the realm of consciousness. A key issue in this controversy is the measurement of consciousness. Experimental conclusions hinge on this basic issue. For example, if consciousness is equated with verbal report of phenomenal experience, it is trivial to show that some stimulus aspects were processed “unconsciously”. Such findings can be considered subjective threshold effects. However, such measures of awareness are inherently flawed. Still, some have claimed that unconscious processing exists even when objective detection measures show null sensitivity (i.e., d′ = 0). This claim has been difficult to validate and is fraught with problems (e.g., the problem of proving the null hypothesis).
Our methodological and theoretical approach to this controversy involves applying a Signal Detection Theory model of joint detection and identification. In this paradigm, detection and identification performance are measured on every trial. We have shown that detection and identification are quantitatively related for simple as well as complex stimuli. This model offers an interpretation for a common example of unconscious perception: Correctly identifying a stimulus following a miss. Such a finding is perhaps unsurprising to sensory psychophysicists. Nonetheless, many cognitive psychologists use tasks that claim to index unconscious processing (e.g., exclusion tasks), but we have shown that these results, too, are likely susceptible to subjective threshold criterion artifacts (Haase & Fisk, 2001). Granted, SDT is neutral regarding consciousness, but our findings do converge with contemporary neural models (e.g., Tononi & Edelman, 1998) emphasizing discriminative and integrative abilities as conscious processes.
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