Attention, Perception, & Psychophysics

, Volume 71, Issue 6, pp 1219–1227

Estimating the difference limen in 2AFC tasks: Pitfalls and improved estimators

Brief Reports


Discrimination performance is often assessed by measuring the difference limen (DL; or just noticeable difference) in a two-alternative forced choice (2AFC) task. Here, we show that the DL estimated from 2AFC percentage-correct data is likely to systematically under- or overestimate true discrimination performance if order effects are present. We show how pitfalls with the 2AFC task may be avoided and suggest a novel approach for analyzing 2AFC data.

Copyright information

© Psychonomic Society, Inc. 2009

Authors and Affiliations

  1. 1.Department of Cognitive and Biological Psychology, Psychological InstituteUniversity of TübingenTübingenGermany
  2. 2.University of MünsterMünsterGermany

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