A Test of Piaget's Explanation of the Müller‐lyer Illusion

Piaget's (1969) explanation of the Müller‐Lyer illusion is tested in an experiment in which the following factors are independently varied: (1) the relationship between the length of the shaft ( A ) and the total length of the figure ( B ), from B = 1·3 A to B = 2·6 A; (2) the angle made by the fins with the shaft, from 120 to 160°. Using 60 subjects, nine illusion figures and a paired‐comparison procedure, the results showed: (1) that the illusion varied systematically with changes in the A:B relationship, though the maximum effect occurred when B = 1·7 A and not when B = 2 A , as found by Piaget; and (2) that the illusion varied directly with the angle of the fins, which is not in line with Piaget's argument. However, some inconsistency was noted between this argument and the values predicted by Piaget's Prop. 15 which correspond more closely with the obtained results. A simplified formula is proposed which predicts the results perfectly with the exception of one illusion figure, which can be treated as a special case

Argument (complex analysis) · Cognitive psychology · Developmental psychology · Illusion · Optical illusion · Test (biology) · Advanced Optical Imaging Technologies · Chemistry · Cultural and Historical Studies · Mechanics and Biomechanics Studies · Psychology