Rhythm in speech and music emerges from the alternation of prominent elements with non-prominent ones so that pitch/intensity signal initial and duration final prominence (Lerdahl & Jackendoff, 1983; Nespor et al., 2008; Langus et al., 2017). However, in the speech signal, these acoustic cues also tend to co-vary dynamically depending on the location of prominence in sentences (Shattuck-Hufnagel & Turk, 1998). Therefore, to perceive suprasegmental rhythm, young infants could benefit from perceiving the covariation of the acoustic cues signaling prominence as categorical. We hypothesize that the ability is domain-general (Liberman, 1967) and should, therefore, be subject to cross-domain effects of experience with spoken language as well as music already during the first year of life (Patel, 2011).
Six-month-old German-learning infants (N=31) listened to trials (N=99) consisting of four instances of the word ‘gaba’ chosen from a lexical stress continuum that co-varied pitch, duration, and intensity cues from trochaic (word-initial) to iambic (word-final). The first three instances provided the context, and the fourth instance the test. We reasoned that Categorical Perception (CP) would entail infants discriminating between-category items from within-
category items and failing to discriminate between within-category items. We assessed the domain-generality of the ability through a questionnaire detailing early exposure to language and music at home through a parental questionnaire.
We show that infants as a group failed to perceive the co-variation of pitch, intensity, and duration as categorical. CP was only observed in infants who had above-average exposure to music or language at home, with the strongest effects of CP observed in infants who had high language as well as musical experience. Early exposure to language and music may, therefore, help young infants to finetune domain-general perceptual mechanisms for perceiving suprasegmental rhythm in spoken language and possibly in music.