Content area
Abstract
Implicit/unconscious learning is responsible for the formation of habits and the mastery of complex motor skills. Often, implicit learning occurs in concert with explicit/conscious knowledge, effort, and intent. However, it remains poorly understood how implicit learning is affected by concurrent explicit processes. In the following set of studies, a novel explicit/implicit motor sequencing paradigm was developed and simultaneously used to investigate the acquisition and consolidation of motor memory. Unlike other paradigms, this paradigm could generate measures of implicit memory in those with and without explicit knowledge during training by removing explicit knowledge from performance measures in certain blocks. This ability is an important one as we could separate the effect explicit knowledge had on the acquisition of implicit learning from the effect explicit knowledge had on performance. This control was made possible by the manipulation of cues and instruction. Those given Incidental instructions (learning is without conscious intent and hence incidental) were never aware of the presence of a pattern throughout training, while those given Intentional instruction (learning is consciously directed) were explicitly aware of the pattern when color cues were present. When these color cues were removed, these Intentional subjects were unaware of the presence of the pattern, although it was identical to that seen in the “Cued” epochs. These uncued epochs (“Probe”) offered measures of implicit memory from which implicit learning could be inferred in both Incidental and Intentional learners. In the first study, this paradigm was tested in younger adults, and it was demonstrated that implicit motor sequence learning occurred to the same extent in Intentional and Incidental learners. When present, explicit knowledge could be used to benefit performance measures for reaction time but not accuracy. The use of explicit knowledge was associated with impaired expression of implicit learning early in training. In the second study, implicit learning was found to be independent of explicit knowledge in older adults as well. However, decreased working memory capacity in this population was associated with failure to explicitly learn the pattern. In the third study, explicit knowledge was found to have no effect on implicit perceptual sequence learning, although concurrent explicit search specifically impaired the expression of implicit perceptual but not implicit motor sequence learning. In the fourth study, explicit knowledge was found to have no effect on the “off-line” consolidation of implicit motor memory. In this study, no evidence of off-line benefits was found to occur with sleep, although wakefulness in the daytime was associated with off-line benefits for general motor skill. These findings are in line with an understanding of implicit learning that is defined not only by its lack of awareness, but also by its automaticity: learning is hidden, constant, incidental, and unaffected by any conscious process except at the level of expression.
