An experimental analysis of the Chevreul pendulum illusion.

An investigation was performed, with the use of 60 male and female college students, to quantify the Chevreul pendulum illusory effect, the tendency of a small pendulum, when suspended from the hand and imaginatively concentrated upon, to oscillate seemingly of its own accord. By means of a time exposure photographic measurement technique, strong parametric influences of the pendulum's sinusoidal motion were isolated. It was found that the pendulum effect was enhanced when (a) attentional capacity remained undivided, (b) the amount of musculature used to suspend the pendulum was at a maximum, (c) oscillating visual and auditory external stimuli were present, and (d) females were Ss. In addition, the visual stimulus was found to be superior to its auditory counterpart. The relevance of ideomotor and visual capture interpretations of covert muscle processes in the pendulum illusion was discussed.