Illusion of extent in simple angular figures

Abstract. With the exception of very small angles (<15°) Ileywood 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 (<75°) 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.