The mechanisms that give rise to the illusion are not well understood, but it seems to have something to do with hemispheric asymmetry. Individual differences in how the illusion is heard often correlate with handedness (ie whether you're left or right-handed)
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In my opinion the most bizarre illusion Professor Deutsch discovered is the "octave illusion".
Be sure to use headphones and prepare to be surprised!
http://philomel.com/musical_illusions/example_octave_illusio...
The mechanisms that give rise to the illusion are not well understood, but it seems to have something to do with hemispheric asymmetry. Individual differences in how the illusion is heard often correlate with handedness (ie whether you're left or right-handed)