Effect of the standard on size of the horizontal-vertical illusion

70 subjects participated in a study designed to replicate the 1968 claim of Gardner and Long that the horizontal-vertical illusion is larger with the vertical than with the horizontal as standard. The effect did not appear in Exp. 1 when subjects made judgments under both the reproduction and graded-series methods but did in a pilot study and in Exp. 2, although more strongly with the method of reproduction.