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)

There is evidence from neuropsychological and psychophysical measurements that conscious sensory information is processed in discrete time segments. The segmentation process may be described as neuronal activity at a frequency of 40 Hz. Stimulus-induced neuronal activities of this frequency are found in the middle latency range of the auditory evoked potential . First, we have studied the effects of different general anesthetics on MLAEP and auditory evoked 40-Hz activity. Second, we investigated MLAEP and explicit and implicit memory for information presented (...) during cardiac anesthesia. In the awake patients peak latencies of the MLAEP were in the normal range. An auditory evoked 40-Hz activity was present 20–100 ms poststimulus. Under nonspecific anesthetics MLAEP and the 40-Hz activity were suppressed, and under receptor-specific agents MLAEP and the 40-Hz activity were partly preserved. None of the cardiac patients had conscious explicit recall of the intraoperative events, whereas some patients showed unconscious implicit memory for an intraoperative tape message. The implicit memory could be related to midlatency auditory evoked potentials. No implicit memory was detectable when MLAEP and the primary cortical processing of the auditory stimuli and 40-Hz activity were blocked. Implicit memory could be detected in more than 50% of the cases when MLAEP, a 30-Hz activity, and the primary cortical stimulus processing were preserved. In conclusion, our observations support the view that a high frequency oscillatory mechanisms, recorded as a grouped neuronal activity in the MLAEP, may be part of a basic neuronal program for conscious sensory information processing. (shrink)

We examined unconscious priming in a stem-completion task with both identity and form-related primes. Participants were given exclusion instructions to avoid completing a stem with a briefly flashed masked word . In Experiment 1, priming of around 7% occurred for both identity and form-based primes at a 33 ms exposure duration. When examining only trials in which the participants failed to identify the prime, this effect increased to 12% for identity primes, but remained the same for form-based primes. In Experiment (...) 2, priming without prime identification was 9% for identity primes, 4% for homophone primes, and 3% for orthographic control primes. Although identity priming was greater than form priming in both experiments, regression analyses revealed that orthographic and phonological overlap alone between the flashed primes and targets could completely account for unconscious identity priming. Hence, we conclude that masked words may only activate their sublexical orthographic and phonological representations and not their lexical representations. (shrink)

Studies investigating memory for events during anesthesia show a confusing pattern of positive and negative results. To establish whether there are any consistent patterns of findings across studies, we conducted a meta-analysis of the data from 2517 patients in 44 studies. The meta-analysis included two measures of the effects of positive suggestions on postoperative recovery: the duration of postoperative hospitalization and the amount of morphine administered via patient-controlled anesthesia, as well as two measures of memory for specific information presented during (...) anesthesia: direct tests and indirect tests. The meta-analysis indicated that positive suggestions presented during anesthesia have little or no effect on postoperative recovery. On the other hand, the meta-analysis showed that specific information is remembered following surgery, as long as testing is not delayed longer than 36 h. Studies of memory for events during anesthesia provide a useful avenue for exploring unconscious cognition. (shrink)