Simple reaction time (RT) and judgment of temporal order (TOJ) are commonly used as methods for estimating perceptual latency. These two measures, however, were shown to dissociate if manipulated by independent variables like stimulus intensity, spatial frequency, color etc.: Usually, reaction time underwent larger changes than TOJ latency.
In our experiment, we investigated the effect of spatial position on TOJ and RT. RT was measured for five temporal loci: 0, 3.5, 7, 15, 30 deg. In the TOJ part, two stimuli were presented: one peripheral and one foveal. The participants’ task was to say which one was presented first. TOJ latency (point of subjective simultaneity) was estimated from the psychometric function by probit analysis. Eight participants took part in the experiments. Each participated in five sessions.
Both RT and TOJ changed with retinal position by about 35 ms. No dissociation was found between the two measures.
In contrast to other factors which affect both RT and TOJ, retinal position did not produce the dissociation usually found. One possible explanation is that the dissociation disappears when the spatial distance between stimuli is large enough.
This study was supported by the A. von Humboldt Foundation
Poster in der Gruppe Wahrnehmung und Aufmerksamkeit II, Mittwoch, 31. März 1999, 17:00-19:00, Foyer 2. Stock
