Effect of the ISI on the visible persistence of a stimulus in apparent motion.
The persistence of briefly flashed stimuli undergoing a horizontal apparent motion is assessed as a function of the temporal interval (inter-stimulus interval or ISI) between successive locations. The main result is that the duration of persistence is increased when the ISI is reduced (within the range 1-15 msec). An increase of persistence also occurs when the spatial separation (delta chi) between successive presentations of the moving stimulus becomes larger, a well established result which is replicated here. In both cases, the elevation of persistence suggests that inhibitory processes, which are assumed to underlie the persistence-suppression, have become less efficient. According to the data, it seems that the spatio-temporal parameters of motion, and not the speed as such, are responsible for the strength of inhibition. Namely, optimal inhibition, and thus suppression, would need a minimum amount of time to take place, and would improve with proximity (i.e. with smaller delta chi). Finally, a persistence-suppression decrease is observed when the angular size of the flashed stimuli is reduced (i.e. when higher spatial frequencies become more predominant). A model of transient-on-sustained inhibition accounts well for these results.
Castet
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Laboratoire de Psychologie Expérimentale, Université René Descartes, CNRS, Paris, France.
D000360:Afterimage / Q000502:physiology*; D005403:Fixation, Ocular; D006801:Humans; D009039:Motion Perception / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology; D009903:Optical Illusions / Q000502:physiology; D013997:Time Factors