SCALING EXTRAVEHICULAR AND EN ROUTE JUDGMENTS OF AUTOMOBILE SPEED.
WASHINGTON UNIV SEATTLE PSYCHOPHYSICS LAB
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Automobiles were used to investigate psychophysical laws which govern judgments of three forms of subjective speed linear speed approach speed and en route speed. By the method of magnitude estimation, subjective values of all three were found to be power functions of their corresponding physical velocities with exponents of 1.00, 1.75, and 1.94. The relation between category and magnitude scales of en route speed was also studied. Characteristic of prothetic continua, the category scales are concave downward when plotted as a function of the magnitude scales. In order to determine the descriptive value of Webers Law for en route velocity, several difference thresholds were taken at velocities from 20 to 60 miles per hour. The results show that Webers fraction, delta II, is constant over this range. Author