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)

How should we measure metacognitive sensitivity, i.e. the efficacy with which observers’ confidence ratings discriminate between their own correct and incorrect stimulus classifications? We argue that currently available methods are inadequate because they are influenced by factors such as response bias and type 1 sensitivity . Extending the signal detection theory approach of Galvin, Podd, Drga, and Whitmore , we propose a method of measuring type 2 sensitivity that is free from these confounds. We call our measure meta-d′, which reflects (...) how much information, in signal-to-noise units, is available for metacognition. Applying this novel method in a 2-interval forced choice visual task, we found that subjects’ metacognitive sensitivity was close to, but significantly below, optimality. We discuss the theoretical implications of these findings, as well as related computational issues of the method. We also provide free Matlab code for implementing the analysis. (shrink)

Introspection, or metacognition, is the capacity to reflect on our own thoughts and behaviours. Here, we investigated how one specific metacognitive ability develops in adolescence, a period of life associated with the emergence of self-concept and enhanced self-awareness. We employed a task that dissociates objective performance on a visual task from metacognitive ability in a group of 56 participants aged between 11 and 41 years. Metacognitive ability improved significantly with age during adolescence, was highest in late adolescence and plateaued going (...) into adulthood. Our results suggest that awareness of one’s own perceptual decisions shows a prolonged developmental trajectory during adolescence. (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)

It has been over a decade and half since Christof Koch and the late Francis Crick first advocated the now popular NCC project, in which one tries to find the neural correlate of consciousness for perceptual processes. Here we critically take stock of what have actually been learned from these studies. Many authors have questioned whether looking for the neural correlates would eventually lead to an explanatory theory of consciousness, while the proponents of NCC research maintain that focusing on correlates (...) is a strategically sensible first step, given the complexity of the problem. My point here is not to argue whether studying the NCC is useful, but rather, to question whether we are really studying the NCC at all. I argue that in hoping to sidestep the difficult conceptual issues, we have sometimes also missed the phenomenon of perceptual consciousness itself. (shrink)

The study of metacognition can shed light on some fundamental issues about consciousness and its role in behavior. Metacognition research concerns the processes by which people self reflect on their own cognitive and memory processes (monitoring), and how they put their metaknowledge to use in regulating their information processing and behavior (control). Experimental research on metacognition has addressed the following questions: First, what are the bases of metacognitive judgments that people make in monitoring their learning, remembering, and performance? Second, how (...) valid are such judgments and what are the factors that affect the correspondence between subjective and objective indexes of knowing? Third, what are the processes that underlie the accuracy and inaccuracy of metacognitive judgments? Fourth, how does the output of metacognitive monitoring contribute to the strategic regulation of learning and remembering? Finally, how do the metacognitive processes of monitoring and control affect actual performance? Research addressing these questions is reviewed, emphasizing its implication for issues concerning consciousness, in particular, the genesis of subjective experience, the function of self-reflective consciousness, and the cause-and-effect relation between subjective experience and behavior. (shrink)

It has been over a decade and half since Christof Koch and the late Francis Crick first advocated the now popular NCC project (Crick and Koch, 1990), in which one tries to find the neural correlate of consciousness (NCC) for perceptual processes. In his chapter in this book Chris Frith provides a splendid review of how neuroimaging has contributed greatly to this project. For the sake of contrast, this chapter takes a more critical stance on what we have actually learned. (...) Many authors have written on whether looking for the neural correlates would eventually lead to an explanatory theory of consciousness, while the proponents defend that focusing on correlates is a strategically sensible first step, given the complexity of the problem (Crick and Koch, 1998;Crick and Koch, 2003). My point here is not to argue whether studying the NCC is useful, but rather, to question whether we are really studying the NCC at all. I argue that in hoping to sidestep the difficult conceptual issues, we have sometimes also missed the phenomenon of perceptual consciousness itself. (shrink)