Visual perception of moving objects: Effects of velocity and direction
Antoniou, Alexandros
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Permalink
https://hdl.handle.net/2142/19643
Description
Title
Visual perception of moving objects: Effects of velocity and direction
Author(s)
Antoniou, Alexandros
Issue Date
1992
Doctoral Committee Chair(s)
Newell, Karl M.
Department of Study
Kinesiology and Community Health
Discipline
Kinesiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Psychology, Experimental
Language
eng
Abstract
The reported experiments were designed to examine the relation between changes in velocity and direction of travel on the perception of a moving object. The effect of these changes on time-to-contact judgements was also investigated. Despite the extensive literature studying the perception of velocity, no substantive conclusions can be drawn as to the relationship between differing motion functions and predictions about time-to-contact. Little has been done to determine bow the perceived velocity changes as a function of the direction of travel in 3-D space. Time-to-contact estimates of objects travelling in different directions relative to the observer has also received little attention. The following two experiments set out to address these two issues. The results of Experiment 1 indicate that objects travelling on a head-on approach to an observer are perceived as travelling faster than those travelling in either an oblique or transverse direction, given the same actual velocity. It is suggested that the symmetrical expansion of any texture element on the object, has a more significant affordance to the observer. This leads to more conservative responses to avoid contact. Experiment 2 set out to investigate this prediction. The results of Experiment 2 show that observer errors in time-to-contact predictions increase with increases in velocity and as the direction of travel moves away from head-on approaches to motion perpendicular to the line of observation. The symmetrical expansion of objects on a head-on approach is a stronger stimulus for making predictions compared to the rate of constriction of the optical gap between the objects and the target. However, these head-on motions also produced significant underestimations of time-to-contact predictions. The results are explained using an affordance theory interpretation in that head-on approaches afford collision for the observer.
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