DIFFERENTIAL EFFECT OF STIMULUS BRIGHTNESS IN VISUAL DURATION DISCRIMINATION
AbstractTwelve subjects participated in duration discrimination experiments with visually marked temporalintervals. Average interval duration was 4.8 seconds; the difference between the first and secondinterval was varied at nine levels. Experimental sessions consisted of two blocks: first (72 trials)with stimuli of equal brightness, second (144 trials) with stimulus brightness varied (brightâ€“dimor dimâ€“bright). Gaussian psychometric functions were fitted to the data and points of subjectiveequality (PSE) estimated for each subject/condition. The PSEs are generally negative, indicating apresentation order effect known from previous studies. In addition, we observe small but significantdifference between PSEs for unequal brightness conditions, brightâ€“dim versus dimâ€“bright. Theseresults bring evidence for a cross-modal interaction between subjective duration and brightness ofthe duration carrier: brighter stimuli are, on average, perceived as shorter. An interpretation interms of the â€˜dual klepsydra modelâ€™ of duration discrimination is attempted.