title: Bias and sensitivity in two-interval forced choice procedures: Tests of the difference model.
abstract: We assess four common claims concerning the two-interval forced choice (2-IFC) procedure and the standard Difference Model of 2-IFC performance. The first two are (1) that it is unbiased and (2) that the structure of the 2-IFC task does not in itself alter sensitivity. The remaining two concern a claimed 2 enhancement in sensitivity in 2-IFC relative to that measured in a Yes-No task. We review relevant past research and re-analyze seventeen experiments from previous studies across three laboratories. We then report an experiment comparing 2-IFC performance with performance in a second task designed to elucidate observers' decision processes. This second task is simply two successive Yes-No signal detection tasks with the same timing as in the 2-IFC experiment. We find little evidence supporting the claims that 2-IFC is unbiased and that it does not alter sensitivity and we also reject the two claims associated with the Difference Model as a model of performance in our own experiment.
authors.affiliation: Department of Psychology, University of Haifa, 31905 Haifa, Israel. yeshurun@research.haifa.ac.il
authors.forename: Yaffa
authors.initials: Y
authors.lastname: Yeshurun
authors.forename: Marisa
authors.initials: M
authors.lastname: Carrasco
authors.forename: Laurence T
authors.initials: LT
authors.lastname: Maloney
mesh_terms: D000465:Algorithms; D002755:Choice Behavior; D004192:Discrimination, Psychological; D006801:Humans; D008960:Models, Psychological; D015233:Models, Statistical; D011601:Psychophysics; D012680:Sensitivity and Specificity; D017603:Signal Detection, Psychological