Perception of Verticality on a Modified Portable Rod-and-Frame Test

Abstract

563 boys from Grades 7 to 11 were tested on a modified version of the portable Rod-and-frame Test (RFT). The absolute sum of RFT errors decreased progressively from Grade 7 through Grade 11 and correlated with Ss' age ( p < .001). About 90% of the total variance of these scores was accounted for by errors in the direction of the tilt of the frame. Errors toward tilt of frame decreased with increasing age, whereas the proportion of errors against the tilt of frame showed an opposite trend. Trials with the frame left off 0° produced a higher absolute sum of RFT errors and larger errors toward tilt of frame than the right-tilt trials. These findings were discussed within a developmental framework and related to studies on the effect of the frame.