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Brett R. Fajen; Scaling information to action in visually guided braking. Journal of Vision 2004;4(8):811. doi: https://doi.org/10.1167/4.8.811.
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Braking to avoid a collision can be controlled by keeping the deceleration required to stop below the maximum deceleration of the brake. As long as the required deceleration is less than the maximum deceleration, it is always still possible to stop by increasing brake pressure. When the required deceleration approaches the maximum deceleration, brake pressure must be increased to avoid a collision. Because maximum deceleration can vary, keeping the required deceleration in this safe region requires calibrating to the strength of the brake. Calibration may be understood in terms of scaling information about the required deceleration in units of maximum deceleration, such that 1.0 separates possible from impossible stops. In Experiment 1, brake strength was manipulated between subjects, and initial distance and time-to-contact varied within subjects. Participants viewed computer generated displays simulating approaches to a stop sign, and used a joystick as a brake to stop as closely as possible to the sign. The required deceleration and direction of brake adjustment were sampled every 200 ms, and used to calculate the likelihood of increasing brake pressure as a function of required deceleration. In all three brake strength groups, the likelihood of increasing brake pressure increased as required deceleration approached the maximum deceleration. When required deceleration was expressed as a percentage of the maximum deceleration, the likelihood of increasing deceleration was the same for all three conditions, suggesting that information about required deceleration is detected in units of maximum deceleration. In Experiment 2, brake strength was manipulated as a randomly-presented within-subjects variable. The likelihood of increasing brake pressure as a function of required deceleration varied with brake strength, suggesting that it takes longer than one trial to recalibrate.
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