Implicit probabilistic sequence learning is independent of explicit awareness

  1. Sunbin Song1,2,5,
  2. James H. Howard, Jr.3,4, and
  3. Darlene V. Howard1,2
  1. 1 Department of Psychology, Georgetown University, Washington, District of Columbia 20057, USA;
  2. 2 Interdisciplinary Program in Neuroscience, Georgetown University, Washington, District of Columbia 20057, USA;
  3. 3 Department of Neurology, Georgetown University, Washington, District of Columbia 20057, USA;
  4. 4 Department of Psychology, Catholic University, Washington, District of Columbia 20064, USA

Abstract

Studies into interactions between explicit and implicit motor sequence learning have yielded mixed results. Some of these discrepancies have been attributed to difficulties in isolating implicit learning. In the present study, the effect of explicit knowledge on implicit learning was investigated using a modified version of the Alternating Serial Response Time (ASRT) task, a probabilistic sequence learning paradigm that yields continuous and relatively pure measures of implicit learning. Results revealed that implicit learning occurred to the same extent, whether or not subjects had explicit knowledge. Some evidence, however, indicated that explicit knowledge could interfere with the expression of implicit learning early in training. In addition, there were dissociations between learning measures, in that reaction time and accuracy were differentially affected by explicit knowledge. These findings indicate that implicit sequence learning occurs independently of explicit knowledge, and help to explain previous discrepant findings.

Footnotes

  • 5 Corresponding author.

    5 E-mail sss35{at}georgetown.edu; fax (202) 687-6050.

  • Article is online at http://www.learnmem.org/cgi/doi/10.1101/lm.437407

  • 6 Though Random-High and Pattern-High trials are identical in terms of triplet frequency, since Random-High trials always follow Pattern-High trials, they are not identical in terms of quad sequence (four successive elements) or higher structure. Low-frequency triplets also differ in terms of quad structure. Local sequential regularities of this sort have been shown to influence RT in previous sequence learning tasks (Soetens et al. 2004). For example, in the present study, quad types can be split into those that contain two repeated pairs (i.e., 1122); a repeated pair in the first (1124), second (1224), or last (1244) position; a run of three in the first position (1112); a trill in the first position (1213); or no repeated elements (1243). Pattern-High trials can occur within all of these quad types, but Random-High trials do not. Similarly, Low-frequency trials do not occur on quads that began with trills or repetitions, nor did they occur on quads with two repeated elements. When all unequally represented quad types of this sort were removed to eliminate local sequential effects, the difference between the Pattern-High and Random-High trials seen in the first session disappeared, whereas the difference between the Low- and both High-frequency trial types remained.

    • Received September 26, 2006.
    • Accepted January 9, 2007.
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