In an earlier paper (Bergstrom 1965) the investigator reported a study of a brightness paradox in the percep- tion of certain luminance gradients in space. The present study was made tot test the hypothesis that an inducing field of higher or lower luminance and with a change of luminance across its area is a critical condition for the paradox to appear. Luminance gradients with one or two inducing fields of constant luminance were compared with the original gradient which-had inducing fields with luminance changes. A magnitude estimation method and a "partitioning" method ere used. The main result was a falsification of the hypothesis. Thus the paradox appeared also in gradients with only one inducing field of constant luminance. But a change of luminance across the inducing field made the paradox much stronger.
Abstract