Illusion of Extent in Simple Angular Figures

With the exception of very small angles (less than 15 degrees) Heywood and Chessell found systematic misestimations of the baseline distances of angles. Here three experiments are reported two of which indicate that the baseline distances of a wide range of acute angles (less than 75 degrees) are overestimated while the third confirms Heywood and Chessell 's pattern of errors. The results are discussed with reference to a possible confounding present in the method used in the third experiment and, therefore, in the original Heywood and Chessell experiments.