Psychonomic Bulletin & Review

, Volume 16, Issue 6, pp 1026–1036

A diffusion model decomposition of the practice effect


    • Department of PsychologyUniversity of Amsterdam
  • Joachim Vandekerckhove
    • Leuven University
  • Francis Tuerlinckx
    • Leuven University
  • Eric-Jan Wagenmakers
    • Department of PsychologyUniversity of Amsterdam
Brief Reports

DOI: 10.3758/16.6.1026

Cite this article as:
Dutilh, G., Vandekerckhove, J., Tuerlinckx, F. et al. Psychonomic Bulletin & Review (2009) 16: 1026. doi:10.3758/16.6.1026


When people repeatedly perform the same cognitive task, their mean response times (RTs) invariably decrease. The mathematical function that best describes this decrease has been the subject of intense debate. Here, we seek a deeper understanding of the practice effect by simultaneously taking into account the changes in accuracy and in RT distributions with practice, both for correct and error responses. To this end, we used the Ratcliff diffusion model, a successful model of two-choice RTs that decomposes the effect of practice into its constituent psychological processes. Analyses of data from a 10,000-trial lexical decision task demonstrate that practice not only affects the speed of information processing, but also response caution, response bias, and peripheral processing time. We conclude that the practice effect consists of multiple subcomponents, and that it may be hazardous to abstract the interactive combination of these subcomponents in terms of a single output measure such as mean RT for correct responses. Supplemental materials may be downloaded from http://pbr

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© Psychonomic Society, Inc. 2009