| The goal of the current study was to demonstrate that decay curves derived from a multi-trial recognition procedure could be decomposed into two components representing the influence of two different memory processes. Prior work with this experimental paradigm had demonstrated that the decay curves were best fit by a negative exponential function. The initial conception was that the decay rate of the exponential reflected the influence of some implicit process and the asymptote the influence of some explicit process. Six experiments were conducted to test this hypothesis. Each manipulated a variable known or suspected to dissociate implicit and explicit memory. In addition to the decay rate and asymptote, each experiment also measured repetition priming and recognition accuracy, more traditional measures of, respectively, implicit and explicit memory.; Experiments 1a and 1b demonstrated that articulatory suppression, which prevents subvocal rehearsal of verbal materials, decreased both overall accuracy and the asymptote but did not affect priming or the decay rate. Experiment 2 utilized a visual search task to suppress rehearsal of unfamiliar visual patterns. Concurrent visual search decreased overall recognition accuracy but had no effect on any of the other measures. The results of these experiments rule out the involvement of rehearsal mechanisms in producing the decay rate. However, despite the fact that suppression had the expected effect on a known explicit measure, the results are inconclusive regarding the effects of rehearsal on the asymptote.; Experiment 3 demonstrated, unexpectedly, that the decay rate was slower for children than for adults. Also, contrary to expectations, children did not differ from adults on any of the other measures. Alcohol decreased accuracy and slowed the decay rate in Experiment 4. Together, Experiments 3 and 4, in which variables that typically affect explicit measures in fact affect the decay rate, suggest that the decay rate is not actually tapping implicit memory. In Experiment 5 depth of processing affected recognition accuracy and the asymptote in the expected directions. The results of these studies support the notion that the decay rate and the asymptote may reflect the operation of different processes, but the processes involved do not seem to be implicit and explicit memory. It is suggested that these results are consistent with the notion that the decay rate reflects changes in short-term functioning of the perceptual system and that the asymptote reflects longer lasting structural changes in the lexical system. |
