An illusion with musical scales

Abstract

A dichotic tonal sequence was constructed, consisting of the repetitious presentation of the C major scale, with successive tones alternating from ear to ear. The scale was presented simultaneously in both ascending and descending form, such that when a component of the ascending scale was in one ear, a component of the descending scale was in the other, and vice versa. Various illusory percepts were obtained, which differed statistically for the two-handedness populations. About 50% of the righthanders obtained a localization illusion, whereby the upper tones of the dichotic sequence were all perceived as emanating from the right earphone, and the lower tones from the left. When the earphone positions were reversed, this percept was maintained with the paradoxical consequence that the earphone which had apparently been emitting the high tones now appeared to be emitting the low tones, and vice versa. Further analysis revealed that this illusion is based on a mechanism different from that underlying the dichotic illusion recently reported by Deutsch [J. Acoust. Soc. Am. 55, S18 (1974)].