The octave illusion and handedness: A replication of Deutsch’s 1974 study

Abstract

The octave illusion was first described by Diana Deutsch in 1974; in this phenomenon, a dichotic sequence of oscillating 400 and 800 Hz sinusoidal tones evokes different illusory percepts. At the same time, the obtained percepts were found to be dependent on the subjects’ handedness. This study investigates the influence of the handedness classification method on the correlation between reported percept and handedness in the octave illusion. After presenting the stimulus, we asked a total of 174 subjects to report their percepts and complete a handedness inventory as well as a speed tapping task. According to the right shift theory of Annett (1972, 2002) and a related study by Kopiez, Galley, and Lehmann (2010), we hypothesized that the use of performance measurement to classify handedness may clarify ambiguous correlations of subjects’ handedness with some obtained illusionary percepts. The results support the general findings of Deutsch but show that stronger effects can be found if hand performance differences are used for handedness classification. A better separation between the handedness groups could be observed, especially for the complex perception patterns.