When the stored representation of the meaning of a stimulus is accessed through the processing of a sensory input it is maintained in an activated state for a certain amount of time that allows for further processing. This semantic activation is generally accompanied by conscious identification, which can be demonstrated by the ability of a person to perform discriminations on the basis of the meaning of the stimulus. The idea that a sensory input can give rise to semantic activation without (...) concomitant conscious identification was the central thesis of the controversial research in subliminal perception. Recently, new claims for the existence of such phenomena have arisen from studies in dichotic listening, parafoveal vision, and visual pattern masking. Because of the fundamental role played by these types of experiments in cognitive psychology, the new assertions have raised widespread interest. (shrink)

This article reports four subliminal perception experiments using the relationship between confidence and accuracy to assess awareness. Subjects discriminated among stimuli and indicated their confidence in each discrimination response. Subjects were classified as being aware of the stimuli if their confidence judgments predicted accuracy and as being unaware if they did not. In the first experiment, confidence predicted accuracy even at stimulus durations so brief that subjects claimed to be performing at chance. This finding indicates that subjects's claims that they (...) are ''just guessing'' should not be accepted as sufficient evidence that they are completely unaware of the stimuli. Experiments 2-4 tested directly for subliminal perception by comparing the minimum exposure duration needed for better than chance discrimination performance against the minimum needed for confidence to predict accuracy. The latter durations were slightly but significantly longer, suggesting that under certain circumstances people can make perceptual discriminations even though the information that was used to make those discriminations is not consciously available. (shrink)

The experiments reported by Snodgrass, Shevrin, and Kopka appear to demonstrate that words are perceived even when overall forced-choice discrimination performance does not deviate from chance. We replicated their critical finding in two separate experiments; our results indicated that the subjects′ preferences for one of the two strategy conditions predicted significant deviations from chance performance in the pop condition, even though the overall performance in this condition did not differ from chance. In addition, we found that task preference had no (...) effect when blank cards rather than words were presented and that the words could not be detected when subjects were simply asked to decide on each trial whether a stimulus had been presented. These results suggest that it is possible to demonstrate perception below an objective threshold defined in terms of overall discrimination performance. As such, the results highlight the importance of considering individual differences in studies of perception without awareness. (shrink)

In two experiments subjects attempted to identify words presented below the objective threshold using two task strategies emphasizing either allowing a word to pop into their heads or looking carefully at the stimulus field . Words were selected to represent both meaningful and structural dimensions. We also asked subjects to indicate their strategy preference and to rate their motivation to perform well. In the absence of conscious perception, both strategy preference and word meaning interacted with strategy condition, mediating the accuracy (...) of subjects′ direct word identification judgments. Motivation also mediated performance. Word structure had no effect. Unconscious perception manifested only in the pop condition, underscoring the importance of task strategy in determining whether subliminal effects are observed. A follow-up control experiment using sham flashes demonstrated that strategy preference and motivation effects were not artifacts resulting from performance feedback cues. (shrink)

The process-dissociation procedure has been used in a variety of experimental contexts to assess the contributions of conscious and unconscious processes to task performance. To evaluate whether motivation affects estimates of conscious and unconscious processes, participants were given incentives to follow inclusion and exclusion instructions in a perception task and a memory task. Relative to a control condition in which no performance incentives were given, the results for the perception task indicated that incentives increased the participants' ability to exclude previously (...) presented information, which in turn both increased the estimate of conscious processes and decreased the estimate of unconscious processes. However, the results also indicated that incentives did not influence estimates of conscious or unconscious processes in the memory task. The findings suggest that the process-dissociation procedure is relatively immune to influences of motivation when used with a memory task, but that caution should be exercised when the process-dissociation is used with a perception task. (shrink)

As an alternative to establishing awareness thresholds, stimulus contexts in which there were either greater conscious or greater unconscious influences were defined on the basis of performance on an exclusion task. Target words were presented for brief durations and each target word was followed immediately by its three-letter stem. Subjects were instructed to complete each stem with any word other than the target word. With this task, failures to exclude target words indicate greater unconscious influences, whereas successful exclusion indicates greater (...) conscious influences. Conscious influences were dominant at long durations , but unconscious influences were dominant at short durations . Performance on the exclusion task successfully predicated both qualitative differences in Stroop priming and qualitative differences in recognition memory previously associated with the different effects of conscious and unconscious influences. Taken together, these results demonstrate that an exclusion task allows both unconscious and conscious influences to be defined in terms of significant deviations from baseline performance. As such, exclusion tasks provide a method for distinguishing conscious from unconscious influences that does not require establishing thresholds for null awareness. (shrink)

Unconscious processes, by whatever name they may be known , are invariably operationalized by the dissociation paradigm, any situation involving the dissociation between two indicators , one of availability and the other, of accessibility , such that, ε>α. Subliminal perception has been traditionally defined by a special case of the dissociation paradigm in which availability exceeds accessibility when accessibility is null . Construct validity issues bedevil all dissociation paradigms since it is not clear what might constitute appropriate indicators that, moreover, (...) are pure and exhaustive. Semantic and theoretic drifts in the recent literature—e.g., the confusion of different versions of the dissociation paradigm, the equation of conscious–unconscious with direct–indirect tests, and the foisting of the criterion of qualitative differences—have tended to undermine emerging theoretic parsimony. On the other hand, a crucial factor has been left out of theory development: time. Both ε and α can rise and fall over time, often asynchronously, and so dissociations may wax and wane and, even, reverse over time. Some laboratory evidence suggests that accessibility measures , as they approach chance, may actually dip below chance . If so, d′=0 , could be an averaging artifact of positive and negative d′s. Conscious accessibility is not either–or but more or less, and variable over time. (shrink)