Visual discrimination, categorical identification, and categorical rating in brief displays of curved lines: Implications for discrete encoding processes

In Exp I with 4 26-36 yr olds, discriminability of pairs of curved lines separated by a constant distance on the s scale was measured at successive points along the scale. Discrimination performance varied nonsmoothly with s. In Exp II with Ss from Exp I, a categorical identification task was performed in which Ss labeled the curved-line stimuli of Exp I straight, just curved, and more than just curved. In Exp III (same Ss), categorical rating scales with 2, 3, and 4 intervals were tested, and each was less effective than the categorical identification scale for predicting discrimination performance. Mean ratings were, however, highly linear with s, suggesting that the curved-line continuum was psychometrically uniform. Exp IV (same Ss) provided further evidence for the uniformity of the curved-line continuum by measuring conventional acuity for curvature. It is concluded that under conditions in which attention is distributed over a number of elements in the field and in which viewing and effective visual-processing time is restricted, performance in discriminating curved-line stimuli may be determined by relatively coarse, discrete visual processes. (59 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1983 American Psychological Association.