Effect of Forced-Choice vs Magnitude-Estimation Measures on the Waveform of Metacontrast Functions*

Abstract
Metacontrast functions were obtained for three subjects using forced-choice and magnitude-estimation response measures, and for a fourth subject using forced choice alone. The functions from these two measures were in every case U shaped and did not differ significantly from each other, even though the stimuli used for each measure differed slightly, and the forced-choice study was done three months after the magnitude-estimation study. Thus, U-shaped metacontrast functions are not artifacts of subjective response criteria. The relative merits of the subjective and objective response indicators as measures of metacontrast are discussed.