Investigating the role of the judgment instructions and pictorial depth information in the perception of relative size was the purpose of this work. In the experiment, observers chose which rectangle of the two presented (standard and test stimulus) was taller on the computer screen. The observers were divided in groups according to the instructions received (apparent or objective) and the kind of texture gradient in which the stimuli were presented. The judgments were not affected by the texture, but predominantly by the experimental instructions. Apparent judgment instructions had more relative errors and favored the underestimation of size of the standard stimulus, while objective judgment instructions favored the overestimation of size. The presence of the horizon line improved more accuracy of judgments of relative size. Judgment instructions and height of the horizon turned out as important factors in the determination of the judgments of relative size visually perceived.
visual perception; instructions; pictorial depth cues
