Time-to-passage judgments on circular trajectories are based on relative optical acceleration

Abstract

Current theories of arrival time have difficulty explaining performance in the common but neglected case of nonlinear approach. Global tau, a variable supposed to guide time-to-passage (TTP) judgments of objects approaching on linear trajectories,does not apply to circular movement. However, TTP judgments are surprisingly accurate in such cases. We simulated movement through a three-dimensional cloud of point-lights on various circular trajectories. Arrival-time judgments were found to be above chance when observers had to determine which of two expansionless targets would pass them first. Similar to the inside bias observed in heading studies on circular trajectories, observers showed a strong bias to select the target on the inside of their own curved motion path as passing by first. Analysis of the projected target motion revealed that targets on the inside had lower optical velocities and relatively high optical acceleration rates. Empirical TTP judgments agreed best with a strategy based on relative optical velocity changes.

Global flow impacts time-to-passage judgments based on local motion cues

“…In other words, more eccentric targets with higher image velocities were consistently perceived to have smaller TTP values than targets with lower image velocities. They further suggested that observers may also rely on image acceleration in addition to image velocity to judge TTP (Kerzel, Hecht & Kim, 2001). In our experiment image acceleration was fixed throughout the stimulus to eliminate potential confounds with motion coherence.…”

Effects of a moving distractor object on time-to-contact judgments.

“…The constantly available tau information is then taken by the visual system to inform decisions such as when to start swinging the baseball bat or when to initiate a braking motion (see, e.g., Tresilian, 1995). More recently, a growing body of literature has suggested that the processor uses simpler, alternate optical variables, such as expansion rates or even simple image velocities (see, e.g., Kerzel, Hecht, & Kim, 2001;Smith, Flach, Dittman, & Stanard, 2001). For instance, performance degrades gracefully when information is diminished to the extent that tau is no longer available, proving that other optical variables as well can be used for TTC estimation.…”

Detection of collision events on curved trajectories: Optical information from invariant rate-of-bearing change

“…Previous research (Rieger, 1983) has suggested that the translational component of the optical flow field and the time derivatives of the velocity field are sufficient for determining the TTC and the angle of approach. Kerzel and colleagues (2001) examined time-to-passage (the time before an object passes by the observer) judgments for objects moving on circular trajectories. They found that an object that passed on an inside trajectory was more likely to be judged as the first to pass the observer.…”