Mislocalization of a moving object in three-dimensional space

Our visual system exhibits systematic biases in localizing visual objects. This is particularly evident when it localizes the position of a moving object. The present study explored the position perception of a visual object moving in depth at a relatively fast velocity for a long distance. Observers viewed an object moving in a constant velocity of 2 m/s per second for 1000 ms, which was either directly approaching toward or receding from them, on a 3D projector. The entire back-ground was flashed at various timings during the movie. After the movie, a probe object was presented at various distance from the observer. The observers judged whether the probe was closer to (or farther away from) them, compared with the perceived position of the moving object at the time of the flash. The results showed that the observers tended to report that the position of the approaching object was farther away and that of the receding object was closer to them, compared with the probe object (i.e., underestimation). However, when the flash occurred early in the approaching condition and there-fore the position to be reported was far away from the observer, the position of the approaching object was reported closer to the observer(i.e., overestimation). Such reversal of mislocalization was not observed in the receding condition. Subsequent experiments revealed that it was the distance from the observer rather than the flash timing relative to the motion onset that determined whether underestimation or overestimation would occur. These results suggest that the visual system might estimate the distance of objects differently for objects approaching toward and those receding from the observer.