title: Estimating the difference limen in 2AFC tasks: pitfalls and improved estimators.
abstract: 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.
authors.affiliation: Department of Cognitive and Biological Psychology, Psychological Institute, University of Tübingen, Friedrichstr. 21, 72072 Tübingen, Germany. ulrich@uni-tuebingen.de
authors.forename: Rolf
authors.initials: R
authors.lastname: Ulrich
authors.forename: Dirk
authors.initials: D
authors.lastname: Vorberg
mesh_terms: D001288:Attention; D004056:Differential Threshold; D004193:Discrimination Learning; D006801:Humans; D007600:Judgment; D011214:Practice, Psychological; D011336:Probability; D011594:Psychometrics / Q000706:statistics & numerical data; D011597:Psychomotor Performance; D011601:Psychophysics; D015203:Reproducibility of Results; D017603:Signal Detection, Psychological