Abstract:
Over the last two decades considerable experimental research in cognitive psychology has been concerned with forms of information processing that appear to be beyond introspective access or conscious representation (Kihlstrom, 1987; Nisbett and Wilson, 1977). Much of this research has focused on the area of learning and memory (Johnson & Hasher, 1987; Reber, 1989), particularly the phenomena where knowledge is gained by subjects who have no awareness that they have acquired this information, and who frequently have neither an intention to learn nor an awareness that they have been involved in learning (Stadler, 1992). Although aspects of this process have been investigated as forms of intuitive processing (Bowers, 1984, 1990; Metcalfe & Wiebe, 1987), the bulk of this research is generally subsumed under the heading of 'implicit', 'incidental,' or 'nonconscious learning' or the 'development of procedural knowledge'.
Experimental procedures to investigate implicit learning generally involve the presentation on a computer monitor of various types of complex stimuli that contain some form of nonsalient structure. One of two most commonly used experimental procedures is the format developed by Nissen and Bullemer (1987) in their investigation of declarative and procedural learning. In this task the subject faces a microcomputer screen on which a light briefly appears in one of four horizontal locations at each trial. Four marked keys of the computer keyboard are aligned with the locations of the light and the task of the subject is to press the appropriate key when the light flashes. The bulk of the experiment is a repeating sequence condition where the lights appear in a set sequence of locations that repeats over the period of the presentation. Subjects are asked only to respond as fast as possible when the target asterisk appears on the screen, and at no time are they told of the presence or absence of a repeating pattern. A consistent finding from this format is that a subject's latency or reaction times decrease with repeated training. In the Nissen and Bullemer (1987) experiment, for instance, the reduction in RTs found after 10 repetitions of the sequence was 100 ms greater than that when the presentation consisted of randomly presented stimuli. Since approximately 19 ms of this decrease was attributed to practice effects, the authors proposed that the subjects had learnt the specific sequence embedded in the presentation.
