title: Optical specification of time-to-passage: observers' sensitivity to global tau.
abstract: Despite its general mathematical formulation, most empirical work on the visual perception of tau (defined as a quantity divided by its temporal derivative) has focused on the case of direct approach, with tau defined as image angle/rate of expansion. Empirical investigators tend to generalize image size analyses to off-axis approaches. However, this generalization is inappropriate for all but a few classes of objects. After mathematically reestablishing the appropriate optical cues specifying time to passage for noncollision cases, we report a series of studies in which we examined observers' sensitivities to this information in both relative- and absolute-judgment paradigms. In general, we found observers' judgments to be accurate and robust.
authors.affiliation: Aerospace Human Factors Research Division, NASA Ames Research Center, Moffett Field, California 94035-1000.
authors.forename: M K
authors.initials: MK
authors.lastname: Kaiser
authors.forename: L
authors.initials: L
authors.lastname: Mowafy
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention; D004215:Distance Perception; D005260:Female; D006801:Humans; D008297:Male; D008433:Mathematics; D009039:Motion Perception; D009949:Orientation; D011601:Psychophysics; D013028:Space Perception; D013998:Time Perception