“…The results of a large number of studies argue for a progressively relaxed cutoff in any discrimination model that postulates a stopping criterion based on S's expected accuracy. These experiments measured time and accuracy when the discrimination difficulty varied randomly from trial to trial (Henmon, 1906;Lemmon, 1927;Kellogg, 1931;Johnson, 1939;Festinger, 1943a, b;Birren & Botwinick, 1955;Botwinick, Brinley, & Robbin, 1948;Thurmond & Alluisi, 1963;Morgan & Alluisi, 1967;Pickett, 1964Pickett, , 1967. For trials on which the more difficult stimuli occurred: (1) mean RTs were slower and (2) error rates were higher.…”