Investigating the differential encoding of rhythm and meter in adults and six-month old infants
From early development, rhythm perception plays a major role in the comprehension and production of spoken language, music, and dance. One process involved in rhythm perception is neural entrainment, where brain oscillations increase and decrease in energy periodically with an external rhythm. When instructed to hear an ambiguous six-beat stimulus in either groups of two (duple meter) or three (triple meter), adults neurally entrain to frequencies at the beat and primed meter levels. However, seven-month-olds who listened to the same stimulus while distracted neurally entrained to the beat, duple, and triple frequencies regardless of priming. This study investigates whether infants can be similarly primed to perceive one metrical interpretation versus another. Infants are presented with a six-beat rhythmic pattern accompanied by a simple video of a circle expanding and shrinking in synchrony with the first beat to capture attention. For repetitions, participants listen to either a ‘duple’ or ‘triple’ accented stimulus. This is followed by 16 repetitions of the unaccented, ambiguous stimulus. To further investigate whether participants maintain perception of a particular metrical structure, pitch-deviant tones on beats four (consistent with triple) and five (consistent with duple) are presented to elicit a mismatch negativity (MMN) response, which is an EEG component associated with violations against expectations. Pilot adult EEG data are being analyzed with the prediction that MMN amplitude will be higher for deviants associated with the primed meter condition. This would demonstrate the use of top-down processing in rhythm perception in infants as early as six-months old.