Abstract
We here report a new class of duration illusion in which the subjective duration of a flash is modulated by up to 30% as a function of its temporal relation to a longer flash. When a brief flash occurs in the presence of a longer flash, its perceived duration is expanded for longer stimulus onset asynchronies (SOAs) and contracted for shorter SOAs. This pattern of perceived duration distortion appears to be related to the hazard function, which describes the probability of an event occurring given that it has not yet occurred. To test this possibility, we varied the probability distribution function of SOAs presented in an experiment session and compared the measured duration distortion to the duration distortion predicted by a model based on the hazard function. Our findings parallel a previous demonstration that perceived brightness is modulated by temporal context (Eagleman et al., 2004), suggesting the possibility of a common mechanism for continuous magnitude comparisons. Other stimulus attributes related to magnitude, such as size and numerosity, may also exhibit illusory changes in perceived magnitude as a function of temporal context.