Fundamental frequency contour (melody) of infant vocalisations across the first year

Introduction: The fundamental frequency contour (melody) of cry and non-cry utterances become more complex with age. However, there is a lack of longitudinal analyses of melody development during the first year of life. 
Objective: The aim of the study is to longitudinally analyse melody development in typical vocalisation types across the first 12 months of life. The aim was twofold: (1) to answer the question whether melody becomes more complex in all vocalisation types with age, and (2) to characterize complex patterns in more detail.
Methods: Repeatedly recorded vocalisations (n=10.988) of 10 healthy infants (6 female) over their first year of life were analysed using frequency spectrograms and fundamental frequency (f0) analyses (PRAAT). Melody complexity analysis was performed using specific in-lab software (CDAP, pw-project) in a final subset of 9.237 utterances that contained noise-free, undisturbed contours. Generalized mixed linear models were used to analyse age and vocalisation type effects on melody complexity.
Results: The vocalization repertoire showed a higher proportion of complex melodies from the second month onwards. The age effect was significant, but no difference was found in melody complexity between cry and non-cry vocalizations across the first six months. From month 7-12, there was a further significant increase in complex structures only in canonical babbling, not in marginal babbling. Melody segmentations by laryngeal constrictions prevailed among complex shapes.
Conclusion: The study demonstrated the regularity of melody development in different vocalisation types throughout the first year of life. In terms of prosodic features of infant sounds, melody contour is of primary importance, and further studies are required that also include infants at risk for language development.

