Octave illusion

Octave illusion.

Discovered by Diana Deutsch in 1973, the octave illusion is an auditory illusion produced by simultaneously playing two sequences of two notes that are spaced an octave apart, high to low, and low to high, in separate stereo channels over headphones. The tones are sine waves of constant amplitude, and switch between high and low four times a second, with no amplitude drops at the transitions. So the listener is presented with a single, continuous two-tone chord, with the ear of input of each component switching repeatedly. (Listen over headphones to the example linked below.)

This pattern is almost never heard correctly, and instead gives rise to a number of illusions. Most people hear a single tone that switches between left and right ears while its pitch simultaneously switches back and forth between high and low. Most right-handers hear the high tone as on the right and the low tone as on the left. When the earphones are reversed most right-handers hear the same thing – the tone that had appeared in the right ear still appears in the right ear and the tone that had appeared in the left ear still appears in the left ear.

Other people experience entirely different illusions; for example they may hear a single high tone in the left ear alternating with a single low tone in the right ear, or obtain complex perceptions that involve three or four tones of different pitch. Right-handers and left-handers vary statistically in how they perceive the octave illusion, with left-handers less likely to hear the high tone on the right, and more likely to obtain complex perceptions.

References

• Deutsch, D. (1974). "An auditory illusion". Nature 251 (5473): 307–309. doi:10.1038/251307a0. PMID 4427654.  Abstract PDF Document
• Deutsch, D. (1974). "An auditory illusion". Journal of the Acoustical Society of America 55: s18–s19. doi:10.1121/1.1919587.  Abstract
• Deutsch, D. (1975). "Musical Illusions". Scientific American 233 (4): 92–104. doi:10.1038/scientificamerican1075-92. 
• Deutsch, D. & Roll, P. L. (1976). "Separate "what" and "where" decision mchanisms in processing a dichotic tonal sequence". Journal of Experimental Psychology: Human Perception and Performance 2 (1): 23–29. doi:10.1037/0096-1523.2.1.23. PMID 1262796.  PDF Document
• Deutsch, D. (1978). "Lateralization by frequency for repeating sequences of dichotic 400 Hz and 800 Hz tones". Journal of the Acoustical Society of America 63 (1): 183–186. doi:10.1121/1.381710. PMID 632409.  PDF Document
• Deutsch, D. & Gregory, A. H. (1978). "Deutsch's octave illusion". Nature 274 (5672): 721–2. doi:10.1038/274721b0. PMID 673008. 
• Deutsch, D. (1980). "Ear dominance and sequential interactions". Journal of the Acoustical Society of America 67 (1): 220–228. doi:10.1121/1.383731. PMID 7354190.  Weblink PDF Document
• Deutsch, D. (1980). "The octave illusion and the what-where connection. In R. S. Nickerson (Ed.)". Attention and Performance VIII: 575–594. 
• Deutsch, D. (1981). "The Octave Illusion and Auditory Perceptual Integration. In Tobias, J.V., and Schubert, E.D". Hearing Research and Theory, Volume 1 1: 99–142. ISBN 0-12-312101-9.  PDF Document
• Deutsch, D. (1983). "The octave illusion in relation to handedness and familial handedness background". Neuropsychologia 21 (3): 289–293. doi:10.1016/0028-3932(83)90047-7. PMID 6877583.  PDF Document
• Deutsch, D. (1983). "Auditory illusions, handedness, and the spatial environment". Journal of the Audio Engineering Society 31: 607–618. 
• Deutsch, D. (1986). "Auditory pattern recognition. In K. Boff, L. Kaufman and J. Thomas (Eds.)". Handbook of Perception and Human Performance 32: 1–44. 
• Deutsch, D. (1987). "Illusions for Stereo Headphones". Audio Magazine: 36–48.  PDF Document
• Deutsch, D. (1988). "Lateralization and sequential relationships in the octave illusion". Journal of the Acoustical Society of America 83 (1): 365–368. doi:10.1121/1.396249. PMID 3343449.  Weblink PDF Document
• Deutsch, D. (1999). "Grouping mechanisms in music. In D. Deutsch (Ed.)". The psychology of music, 2nd Edition: 299–348.  PDF Document
• Deutsch, D. (2004). "The Octave Illusion Revisited Again". Journal of Experimental Psychology: Human Perception and Performance 30 (2): 355–364. doi:10.1037/0096-1523.30.2.355. PMID 15053694.  PDF Document
• Deutsch, D. (2004). "Reply to Reconsidering evidence for the suppression model of the octave illusion, by C.D. Chambers, J.B. Mattingley, and S.A. Moss". Psychonomic Bulletin and Review 11 (4): 667–676. doi:10.3758/BF03196618.  PDF Document

External links

• Diana Deutsch's octave illusion page at UCSD
• Stereo Sound Example of Deutsch's Octave Illusion