Tracking the apparent location of targets in interpolated motion

Under appropriate conditions, a target moving in discrete steps can appear to move smoothly and continuously even within the portions of the path wher e no physical stimulus is present. We investigated the nature of this inter polated motion in attentive tracking displays as well as apparent motion. T he results showed that the apparent location of the target moved smoothly t hrough space between the two discrete locations and the judgements of inter polated motion for attentive tracking and apparent motion were comparable t o those for continuous motion in both the perceived path and the precision of the judgements. There were few, if any, differences between judgements f or real and interpolated motion. An alignment procedure showed that the smo oth change in location judgements was real and not a consequence of averagi ng across discrete locations actually seen on each trial. We also found tha t the slowest alternation rate which supported accurate location judgements corresponded to a critical SOA of about 500 ms, similar to the longest SOA which supported a subjective impression of motion in the display. Deviatio ns from a constant velocity which were shorter than 200 ms did not register in the judged motion path, suggesting a fairly long time constant for the integration of velocity information into the perceived motion. These result s suggest a specialized motion analysis which provides an accurate, explici t model of the interpolated motion path. (C) 2000 Elsevier Science Ltd. All rights reserved.