A number of ways of taxonomizing human learning have been proposed. We examine the evidence for one such proposal, namely, that there exist independent explicit and implicit learning systems. This combines two further distinctions, between learning that takes place with versus without concurrent awareness, and between learning that involves the encoding of instances versus the induction of abstract rules or hypotheses. Implicit learning is assumed to involve unconscious rule learning. We examine the evidence for implicit learning derived from subliminal learning, (...) conditioning, artificial grammar learning, instrumental learning, and reaction times in sequence learning. We conclude that unconscious learning has not been satisfactorily established in any of these areas. The assumption that learning in some of these tasks is predominantly based on rule abstraction is questionable. When subjects cannot report the “implicitly learned” rules that govern stimulus selection, this is often because their knowledge consists of instances or fragments of the training stimuli rather than rules. In contrast to the distinction between conscious and unconscious learning, the distinction between instance and rule learning is a sound and meaningful way of taxonomizing human learning. We discuss various computational models of these two forms of learning. (shrink)

When consciousness is examined using subjective ratings, the extent to which processing is conscious or unconscious is often estimated by calculating task performance at the subjective threshold or by calculating the correlation between accuracy and awareness. However, both these methods have certain limitations. In the present article, we propose describing task accuracy and awareness as functions of stimulus intensity as suggested by Koch and Preuschoff . The estimated lag between the curves describes how much stimulus intensity must increase for awareness (...) to change proportionally as much as accuracy and the slopes of the curves are used to assess how fast accuracy and awareness increases and whether awareness is dichotomous. The method is successfully employed to assess consciousness characteristics on data from four different awareness scales. (shrink)

The Objective Threshold/Strategic Model proposes that strong, qualitative inferences of unconscious perception can be made if the relationship between perceptual sensitivity and stimulus visibility is nonlinear and nonmonotonic. The model proposes a nadir in priming effects at the objective identification threshold . These predictions were tested with masked semantic priming and repetition priming of a lexical decision task. The visibility of the prime stimuli was systematically varied above and below the objective identification threshold. The obtained relationship between prime visibility and (...) priming facilitation was nonlinear, but the results failed to confirm a nadir in priming effects at the objective identification threshold. We conclude that the objective identification threshold does not necessarily indicate the point where presumably unconscious priming effects might be inhibited by conscious cognitive processes. (shrink)

What is the best way of assessing the extent to which people are aware of a stimulus? Here, using a masked visual identification task, we compared three measures of subjective awareness: The Perceptual Awareness Scale , through which participants are asked to rate the clarity of their visual experience; confidence ratings , through which participants express their confidence in their identification decisions, and Post-decision wagering , in which participants place a monetary wager on their decisions. We conducted detailed explorations of (...) the relationships between awareness and identification performance, looking to determine which scale best correlates with performance, and whether we can detect performance in the absence of awareness and how the scales differ from each other in terms of revealing such unconscious processing. Based on these findings we discuss whether perceptual awareness should be considered graded or dichotomous. Results showed that PAS showed a much stronger performance-awareness correlation than either CR or PDW, particularly for low stimulus intensities. In general, all scales indicated above-chance performance when participants claimed not to have seen anything. However, such above-chance performance only showed when we also observed a correlation between awareness and performance. Thus PAS seems to be the most exhaustive measure of awareness, and we find support for above-chance performance in the absence of subjective awareness, but such unconscious knowledge only contributes to performance when we observe conscious knowledge as well. Similarities and differences between scales are discussed in the light of consciousness theories and response strategies. (shrink)