Experimental test of the relation of confidence with the time errors in the method of constant stimuli

Abstract

The experiment reported here tested the common belief that comparative judgments become biased because response habits intervene when the observer feels uncertain about which response to give. Using the method of constant stimuli, observers were shown a train of lines, each separated by a 5-sec interval. The observer compared the length of each line with the length of the line immediately preceding it. In addition to making the comparative judgment, the observer had to rate the degree of confidence he/she had in determining that the last line seen was different in length from the immediately preceding line. The results showed that (1) degree of confidence was progressively lowered (slightly) as the number of responses increased, (2) degree of confidence was higher when the last line seen was a variable (even if the observer did not know which was the standard or the variable), and (3) time errors also occurred when the observer was completely certain that there was a difference in length between the compared lines. It may be concluded that the observer’s state of uncertainty did not activate any preexisting response habit. The results seem to fit an inferential-decision theory of comparative judgment.