Melody Pattern Analysis

In agreement with preceding studies, the analysis of melody pattern was based on a differentiation between simple (singe-arc) and complex melodies (Fig. 2a, b). Complex melodies were defined as exhibiting ≥ two arcs and/or intra-melodic breaks between arcs by laryngeal constrictions that generate rhythmical variations [11, 31]. Preceding studies defined a melody arc as being longer than 150 ms and as exhibiting a frequency modulation amplitude (FM amplitude) of at least three (cry) or two (non-cry) semitones [12]. However, we applied a stronger time criterion and adjusted the FM amplitude criteria for arc definition to vocalization type: arc duration was defined to require more than 300 ms and a minimum FM amplitude of two (cry), one and a half semitones (non-cry), or of one semitone (marginal and canonical babbling), respectively. This distinction was justified because Wermke and Mende [12] characterized melody arcs using a mathematical modeling approach and reported a decreasing FM amplitude from crying toward babbling of six to eleven percent, i.e., one up to two semitones. The criteria defined here took this into account.

a, b Melody/intensity diagrams. Melody (black) and intensity (gray) curve of a single-arc melody (a) and complex, triple-arc melody (b).

Based on the mentioned arc criteria, all vocalization melodies were objectively subdivided into those with only a simple (single-arc, SA) melody and those with a complex (multiple-arc, MA) melody (cf. Fig. 2a, b). SA contained a single ascending-then-descending melody arc with a minimum duration of 300 ms. Complex melodies consisted of two (DA), three (TA), or more (MA) melody arcs, each arc having a duration of at least 300 ms. Following earlier work [11, 29], we also identified rhythmically segmented contours (SEG) which contain inner-melodic pauses caused by laryngeal constrictions [31]. Complex melodies of pre-speech utterances regularly exhibit rhythmical variations generated by short “segmentation pauses” between adjacent melody arcs across the first year of life (Fig. ​(Fig.33).

Time waveform and narrow-band (45 Hz) spectrogram displaying a cry utterance consisting of a complex, segmented melody with the following structure: single arc (symmetric shape) − laryngeal constriction (segmentation pause S) − single arc (falling shape) − laryngeal constriction (incomplete segmentation S) − double arc (combination falling-symmetric arc). The subsequent inspiratory noise (ingressive phonation IP) is also visible.

Melodies containing at least one complete or incomplete laryngeal constrictions [11, 31] were assigned to “segmented” complex contours (SEG) independent of arc numbers.