Light intensity in the rod-and-frame test reconsidered

Abstract.— Previously collected data (Nyborg, 1972) on the perception of the vertical in the Rod-and-Frame Test (RFT) were reanalysed according to the method of signed errors presented by Nyborg (1974). Regression analysis showed no systematic relationship between light intensity and frame dependence and that the effect of light intensity on the perception of vertical in the RFT in general is negligible, thus confirming the conclusions drawn originally.