Nature versus nurture in the detection of sour notes
Culturally prominent musical scales such as the diatonic major scale make use of the simple frequency ratios 2:1, 3:2, and 4:3 between notes. Are these ratios intrinsically advantageous for the perceptual encoding of melodies? We trained 48 young adults to detect “sour notes” in isochronous melodies of pure tones based on various musical scales, including novel ones. Frequency ratio simplicity was manipulated in three experiments employing overall eight scales. On each trial, two successive melodies were presented. Melody 1 randomly ordered the notes defining a certain standard scale, in a randomly selected frequency range. Melody 2 was another random ordering of the same tones, with or without a 1-semitone error in one tone. Listeners had to indicate if melody 2 contained an error or not. The standard scale was fixed within each test session, and feedback was provided on each trial. At least 10 successive test sessions – more than 2000 trials, up to 5280 in some cases – were run for each standard scale. For most of the scales, including the diatonic major scale, practice largely improved performance. Performance was also systematically favored by frequency ratio simplicity. Crucially, the benefit of frequency ratio simplicity was not smaller at the end of practice, when for each scale performance was presumably optimal or nearly optimal, than in the initial test sessions. Thus, frequency ratio simplicity appeared to be intrinsically (i.e., naturally) advantageous, at odds with the idea that its benefit might stem from a musical acculturation process pre-existing to this study.