Know thyself: Metacognitive networks and measures of consciousness

Subjective measures of awareness rest on the assumption that conscious knowledge is knowledge that participants know they possess. Post-Decision Wagering (PDW), recently proposed as a new measure of awareness, requires participants to place a high or a low wager on their decisions. Whereas advantageous wagering indicates awareness of the knowledge on which the decisions are based, cases in which participants fail to optimize their wagers suggest performance without awareness. Here, we hypothesize that wagering and other subjective measures of awareness reflect metacognitive capacities subtended by self-developed metarepresentations that inform an agent about its own internal states. To support this idea, we present three simulations in which neural networks learn to wager on their own responses. The simulations illustrate essential properties that are required for such metarepresentations to influence PDW as a measure of awareness. Results demonstrate a good fit to human data. We discuss the implications of this modeling work for our understanding of consciousness and its measures.     

Measuring consciousness: relating behavioural and neurophysiological approaches

The resurgent science of consciousness has been accompanied by a recent emphasis on the problem of measurement. Having dependable measures of consciousness is essential both for mapping experimental evidence to theory and for designing perspicuous experiments. Here, we review a series of behavioural and brain-based measures, assessing their ability to track graded consciousness and clarifying how they relate to each other by showing what theories are presupposed by each. We identify possible and actual conflicts among measures that can stimulate new experiments, and we conclude that measures must prove themselves by iteratively building knowledge in the context of theoretical frameworks. Advances in measuring consciousness have implications for basic cognitive neuroscience, for comparative studies of consciousness and for clinical applications.     

Auditory negative priming in speeded reactions and temporal order judgements

Two experiments are reported that demonstrate negative priming for auditory stimuli. Reaction times and temporal order judgements were used as the dependent measures in Experiments 1 and 2, respectively. In Experiment 1, participants classified tones presented to one ear as wind or string instruments while ignoring tones presented to the other ear. The task was identical for both the prime and the subsequent probe presentations. Probe reactions were slower for previously ignored tones than for tones that had not occurred during the prime presentation. Probe reactions to previously attended tones were faster than reactions to nonrepeated tones. In Experiment 2, the probe reactions were replaced by temporal order judgements. The probability of accepting a tone as antecedent was lower for previously ignored primes than for new tones. No difference was observed between previously attended and new tones. The results are compatible with the conclusion that distractor inhibition is a necessary component of the processes that bring about observable negative priming phenomena.     

Artificially induced valence of distractor words increases the effects of irrelevant speech on serial recall

In a game context, nonwords either were artificially associated with negative valence or were in some sense neutral or irrelevant. Subsequently, participants memorized target words in silence or while attempting to ignore the negatively valent, irrelevant, or neutral auditory distractor nonwords. The presence of distractor nonwords impaired recall performance, but negative distractor nonwords caused more disruption than neutral and irrelevant distractors, which did not differ in how much disruption they caused. These findings conceptually replicate earlier results showing disruption due to valence with natural language words and extend them by demonstrating that auditory features that may possibly be confounded with valence in natural language words cannot be the cause of the observed disruption. Explanations of the irrelevant speech effect within working memory models that specify an explicit role of attention in the maintenance of information for immediate serial recall can explain this pattern of results, whereas structural models of working memory cannot.     

ERP correlates of auditory negative priming

Negative priming refers to slowed down reactions when the distractor on one trial becomes the target on the next. Following two popular accounts, the effect might be due either to inhibitory processes associated with the frontal cortex, or to an ambiguity in the retrieval of episodic information. We used event-related brain potentials (ERPs) to identify the processing stage primarily associated with negative priming. In an auditory categorization task, reactions in negative priming trials were compared to reactions in a standard control (unrelated primes and probes) and a repetition control (attended prime=ignored probe) condition. Reactions were slower for negative priming than for standard control (Delta32 ms) and repetition control trials (Delta64 ms). The corresponding ERP effect was reflected in an attenuation of a sustained parietal positivity extending from 300 to 600 ms. Because corresponding ERP components were found to be sensitive to stimulus recognition and familiarity, the results may be interpreted to support an episodic retrieval account of negative priming.     

The efficiency of holistic template matching in the recognition of unconstrained handwritten digits

Summary Psychological evidence suggests that simple visual patterns can be recognized by the use of internal representations as holistic templates, but the efficiency of holistic template matching in the recognition of real-life patterns, such as handwritten characters, has been doubted. To clarify this issue, we measured the efficiency of holistic template matching in machine recognition of totally unconstrained handwritten digits. Our learning and recognition algorithm was simple; no previous knowledge of handwritten digits was presupposed, and preprocessing was limited to Gaussian smoothing and normalization with respect to position, size, and orientation. For patterns presented in a known orientation, recognition rates were .69, .77, and .88, respectively, when about 5, 10, or 50 templates had been learned for each type of digit. For patterns presented in unknown orientations, recognition rates were slightly lower. High levels of reliability could be attained by the discounting of classifications based on weak evidence. Apparently, in high reliability recognition, holistic template matching can be used as a first operation by which recognition is achieved for most of the handwritten digits that are seen in real life.     

The dependency of the validity of information integration on cognitive variables and the judgement task

Simple models of information integration focus essentially on the combination of the components of information. This research investigated whether cognitive variables in the constructs of intelligence and cognitive complexity, as well as concentration, could predict the conditions of simple models of judgement. As additional predictors, the two qualitative variables [type of information] and [experience of the judgement task] were introduced. Subjects judged three types of stimuli using the pair comparison method. The conditions of the judgement models were analysed in the framework of the conjoint-measurement approach. Five different regression functions provided mediocre approximations to the 10 conditions of the models, when the 9 cognitive variables were considered. The small differences did not favour one of the five functions. The introduction of the qualitative predictor [type of information] improved the estimations more clearly than the experience of the judgement task, the effect of which was small.     

Auditory negative priming in younger and older adults

Two experiments are reported in which performance of old and young adults in an auditory negative priming task was compared. Auditory negative priming was not smaller in old than in young adults. This result was independent of whether or not conditions were present that had previously been assumed to favour episodic retrieval, as opposed to inhibitory processes, as a basis of the negative priming phenomenon. The data from the present auditory negative priming experiments are incompatible with the global assumption that the efficiency of inhibitory attentional processes in general diminishes across the adult life span.