Abstract
The mechanisms of time perception have consequences for perceived position when one attempts to determine the position of a moving object at a particular time. While viewing a luminance-defined blob orbiting fixation, our observers report the blob's perceived position when the fixation point changes color. In addition to the error in the direction of motion (flash-lag effect), we find that the standard deviation of position judgments increases over a five-fold range of speeds such that it corresponds to a constant 70–80 ms of the blob's trajectory (also see Murakami 2001). This result is in sharp contrast to acuity tasks with two objects moving together, for which thresholds vary very little with velocity. If the 70 ms of temporal variability is dependent on low-level factors, we would expect a different result when we triple the eccentricity, but this had little effect. If the variability is due to uncertainty about the time of the color change, then we should be able to reduce it by using a sound as the time marker (as the auditory system may have better temporal resolution) or by using a predictable event, such as the time a dot moving at a constant velocity arrives at fixation. Although average error differs substantially for these conditions, in both the reported positions still spanned about 70-80 ms of the blob's trajectory. Finally, when observers attempt to press a button in time with arrival of the blob at a landmark, the standard deviation of their errors is about 70 ms. We theorize that this temporal imprecision originates in the same mechanisms responsible for the poor temporal resolution of feature-binding (e.g. Holcombe & Cavanagh 2001; Fujisaki & Nishida 2005).