Using pitch discrimination tasks to tease apart the effects of pitch height and octave equivalence in our perception
Notes separated by a doubling in frequency (or an “octave”) sound similar, a phenomenon named “octave equivalence”. While this relationship is used in musical cultures around the world, it has been remarkably difficult to demonstrate experimentally, with many past studies finding contradictory results. Hoeschele et al. (2012) were perhaps most successful in demonstrating octave equivalence in adults, using a three-range discrimination task. There, participants were trained to respond only to one of three ranges of notes of octave four. A subsequent testing phase showed that participants generalized the discrimination from octave four to octave five. Here we explored why and how this task worked, to better understand the roots and potential cross-cultural significance of octave equivalence. We show that three ranges were crucial to demonstrating octave equivalence: Participants completing analogous two-range tasks do not show octave equivalence and rely solely on pitch height information. We also show that octave equivalence may be limited to neighbouring octaves and that speaking a tonal language does not influence octave equivalence abilities. These results support current hypotheses on the biological origins of music suggesting that octave equivalence is a universal human phenomenon that occurs primarily because the harmonic structure of vocalizations contain octave information.