Influence of the rate of contrast change on the quality of contrast sensitivity assessment: a comparison of three psychophysical methods

Criterion‐free forced‐choice procedures for measuring contrast sensitivity with a cathode ray tube (CRT) have low within‐subject, intersubject, and test–retest variabilities, but a long test time compared with psychophysical methods that rely on the subject's criterion to determine threshold. Test time and variability of criterion‐dependent methods depend on the rate at which the contrast changes on the CRT display. This study compared two criterion‐dependent psychophysical methods for measuring contrast sensitivity (the method of increasing contrast and the von Békésy tracking method) with a criterion‐free two‐alternative forced‐choice procedure. A range of rates of contrast change was studied: 0.1, 0.3, 0.5, 0.7 and 1.0 log unit s−1. Contrast sensitivity, within‐subject variability, intersubject variability, test–retest variability, and test time of the three methods were compared. The 2‐AFC procedure performed best with regard to within‐subject, intersubject, and test–retest variabilities. A time‐efficient alternative was the von Békésy tracking method at rates between 0.1 and 0.5 log unit s−1.