Effects of stimulus order on discrimination sensitivity for short and long durations

Previous studies have shown that discrimination sensitivity in 2AFC tasks depends on the presentation order of the standard and comparison stimulus. The present study examined whether this so-called Type B effect generalizes across different standard magnitudes. Therefore, Experiment 1 employed an auditory duration discrimination task with short (100 ms) and long (1,000 ms) standard durations and a constant interstimulus interval (ISI) of 1,000 ms. For both standard durations, a clear Type B effect emerged. In Experiment 2, discrimination sensitivity was assessed for short (300 ms) and long (1,000 ms) ISIs and a constant standard duration of 100 ms, in order to examine whether the Type B effect diminishes or even reverses when both stimuli are presented in rapid succession, as was suggested by previous studies. In the short, but not the long ISI condition, the Type B effect was virtually eliminated. Taken together, the present experiments suggest that the Type B effect is robust across standard magnitude, but diminishes when the time interval between both stimuli is reduced. This result pattern is discussed within the framework of the Internal Reference Model and the Sensation Weighting Model. It is also demonstrated that both models provide a quantitative account of the present results.