On estimating the difference limen in duration discrimination tasks: A comparison of the 2AFC and the reminder task

Abstract

This article assesses whether the two-alternative forced-choice (2AFC) and the reminder tasks (i.e., method of constant stimuli) yield identical estimates of the difference limen (DL). In a series of six experiments, participants discriminated between two duration stimuli. Experiments 1-5 employed auditory stimuli, and Experiment 6 employed visual stimuli. Experiments 1 and 2 combined each of the two tasks with an adaptive and a nonadaptive procedure for threshold estimation. Experiment 3 varied the distribution of the comparison levels, whereas Experiment 4 employed random interstimulus intervals. Experiments 5 and 6 examined the influence of the presentation order of the standard and comparison stimuli. Results indicate that both the adaptive and the nonadaptive procedures yield virtually identical DL estimates; yet, the 2AFC task produces consistently larger DLs than does the reminder task. In addition, DL increases when the standard occurs in the second rather than in the first stimulus position. In order to account for these results, we assume that participants use an internal standard instead of the actually presented standard as a reference for their judgment.

Reminder and 2AFC tasks provide similar estimates of the difference limen: A reanalysis of data from Lapid, Ulrich, and Rammsayer (2008) and a discussion of Ulrich and Vorberg (2009)

“…The 2AFC task used by Lapid et al (2008) differed from the reminder task in two respects. One was that the order of presentation of standard and comparison stimuli was randomized, so that on any given trial either stimulus could be presented in the first interval with the same probability.…”

“…The inappropriateness of the psychometric function fitted by Lapid et al (2008) to 2AFC data is best described via comparison with the function that they fitted to data from the reminder task. This latter psychometric function was ( ; , ) exp [ …”

“…The reminder task used by Lapid et al (2008) consisted of two intervals designed in such a way that the standard stimulus was always presented in the first interval, with the comparison stimulus always presented in the second. Nonetheless, their Experiments 5 and 6 used what they referred to as an "irregular condition," in which the standard was always presented in the second interval.…”

“…© Lapid, Ulrich, and Rammsayer (2008) reported that estimates of the difference limen (DL) from a twoalternative forced choice (2AFC) task are higher than those obtained from a reminder task. This article reanalyzes their data in order to correct an error in their estimates of the DL from 2AFC data.…”

“…The series of trials can be designed and arranged according to diverse criteria, yielding psychophysical methods that are given different names. Lapid, Ulrich, and Rammsayer (2008) have addressed experimentally the question of whether two of these methods-namely, the reminder task and the two-alternative forced choice (2AFC) task (thoroughly described in the next section)-yield comparable DL estimates. Conventional wisdom has it that both tasks should yield the same outcomes within sampling error, but in a series of experiments, Lapid et al gathered evidence indicating that the 2AFC task produces consistently larger DLs than the reminder task.…”