| Abstract: | There are many claims that stimuli too weak to be detected can affect behavior in powerful ways. There are also many counterclaims that such phenomena are artifacts. The origins of the subliminal perception controversy are traced and some of the problems with the concepts of threshold and awareness are noted. It is suggested that any treatment of the phenomenon must consider the implications of Signal Detection Theory. The basic concepts of the theory are reviewed and the controversy is translated into its terminology. Some studies on masked-primes are summarized and evaluated within that context. While It is possible to obtain an effect for primes that are below a level of claimed awareness, such a subjective definition of the threshold is often problematic, because it confounds stimulus detectability with response bias. When an objective definition is adopted (i.e., d' = O), and proper psychophysical methods are followed, there is no support for the effectiveness of undetectable stimuli. Lastly, a recent approach is briefly described which uses phenomenal awareness as a basis for distinguishing between conscious and unconscious perceptual processes. |
