VERNIER ACUITY WITH DOT TEST OBJECTS

Vernier thresholds were determined as a function of dot number, dot arrangement, and dot separation. The thresholds for a three-dot target with the middle dot movable were less than the thresholds for a two-dot target and for a three-dot target with the bottom dot movable. The thresholds for a two-dot target and for a three-dot target with the bottom dot movable were not reliably different. For both two- and three-dot targets, the thresholds increased as a linear function of interdot separation. The results are interpreted as supporting the hypothesis that vernier judgments with dot stimuli involve primarily a discrimination of orientation rather than of alignment. The results further suggest that information about orientation is not given directly but derived from position information. © 1979.