IS VISION METRIC - COMMENT ON LAPPIN AND LOVE (1992)

In a recent paper, Lappin and Love (1992) showed that depth judgments, based on planar motion of a stimulus, are remarkably precise This led them to the conclusion that perception of planar motion allows acquir ing metric information about visual space. We show, however, that Lapp in and Love's stimuli contained 2-D cues in the frontal plane that cou ld subserve the subject's judgments. This means that high precision in this task does not necessarily imply metric structure of visual space .