DIFFERENTIAL EFFECT OF STIMULUS BRIGHTNESS IN VISUAL DURATION DISCRIMINATION

  • Jiˇrí Wackermann
  • Nina Meyer Blankenburg

Abstract

Twelve 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 (bright–dimor dim–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, bright–dim versus dim–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 ‘dual klepsydra model’ of duration discrimination is attempted.
Section
Full Articles