Melodic contours of maternal humming to preterm infants in kangaroo care and infants' overlapping vocalizations: A microanalytical study

Tonal or melodic contours of maternal voice directed to infants play a role in infants' self-regulation and vocal responsiveness. However, we are unaware about melodic contours of maternal humming directed to preterm infants and its role for infants' vocal responsiveness. We aimed (1) to identify the melodic contours (sinusoidal, bell-shaped, U-shaped, rising, falling, and linear contours) of maternal humming directed to preterm infants in kangaroo care and (2) to identify preterm infants' overlapping vocalizations in each humming melodic contour. Mothers (N = 36) were invited to speak and to hum (using an improvised melody) for their preterm infants during kangaroo care. A temporal segmentation (frequency and lengths) of melodic contours of humming, and descriptive comparative analyses were performed. We found a predominance of sinusoidal contours, followed by bell-shaped, rising, falling, U-shaped, and, finally, linear contours. Also a predominance of infants' overlapping vocalizations was found in sinusoidal and in bell-shaped contours. This study underlines the role of melodic contours of maternal humming to preterm infants, highlighting its communicative functions for the vocal engagement of preterm infants during kangaroo care.