Vocal melodies sung without lyrics (la la) are remembered better than instrumental melodies. What causes the advantage? One possibility is that vocal music elicits subvocal imitation, which could promote enhanced motor representations of a melody. If this motor interpretation is correct, distracting the motor system during encoding should reduce the memory advantage for vocal over piano melodies. In Experiment 1, participants carried out movements of the mouth (i.e., chew gum) or hand (i.e., squeeze a beanbag) while listening to 24 unfamiliar folk melodies (half vocal, half piano). In a subsequent memory test, they rated the same melodies and 24 timbre-matched foils from '1-Definitely New' to '7-Definitely Old'. There was a memory advantage for vocal over piano melodies with no effect of group and no interaction. In Experiment 2, participants carried out motor activities during encoding more closely related to singing, either silently articulating (la la) or vocalizing without articulating (humming continuously). Once again, there was a significant advantage for vocal melodies with no effect or interaction of group. In Experiment 3, participants audibly whispered (la la) repeatedly during encoding. Again, the voice advantage was present and did not differ appreciably from prior research with no motor task during encoding. However, we observed that the spontaneous phase-locking of whisper rate and musical beat tended to predict enhanced memory for vocal melodies. Altogether the results challenge the notion that subvocal rehearsal of the melody drives enhanced memory for vocal melodies. Instead, the voice may enhance engagement.
Keywords: Articulatory suppression; Memory; Music; Singing; Timbre.
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