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Asad Saidpour, George J. Andersen; Use of Speed Information in Detecting Collision Events. Journal of Vision 2002;2(7):347. doi: 10.1167/2.7.347.
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© ARVO (1962-2015); The Authors (2016-present)
We used a speeded response paradigm to determine whether observers use tau to detect collision events when multiple moving objects are present. Tau is an optical variable specified by the inverse rate of expansion of an approaching object that indicates the time to contact (TTC) and is independent of the speed of the observer and/or object. In the present study we examined whether observers' simulated speed affects their response time to detect a collision event when multiple moving objects are present. Observers were shown displays simulating a roadway extended in depth. Within the scene objects were present that translated independently of the observer's motion. The size of the objects was randomly varied within a range. On each trial observers were presented with a variable number of objects in the scene and were asked to indicate whether or not an object was on a collision path with the observer and that they should respond as quickly but as accurately as possible. To determine whether other factors such as observer speed are important we systematically varied the speed of the object and observer motion such that the TTC was constant across a range of object motion and observer motion conditions. If observers use TTC then variations in observer/object speed should not influence their response time to detect a collision event. The results indicated significant variations in response time to detect a collision event as a function of different combinations of object and observer motion across three different values of TTC. Response time increased with an increase in the number of objects in the scene. The results illustrate that subjects use speed information of the surrounding scene to detect collision events and that tau is not the only source of information for the detection of collision events.
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