Temporal patterns in the complexity of child-directed song lyrics reflect their functions

Content produced for young audiences is structured to present opportunities for learning and social interactions. This research examines multi-scale temporal changes in predictability in Child-directed songs. We developed a technique based on Kolmogorov complexity to quantify the rate of change of textual information content over time. This method was applied to a corpus of 922 English, Spanish, and French publicly available child and adult-directed texts. Child-directed song lyrics (CDSongs) showed overall lower complexity compared to Adult-directed songs (ADsongs), and lower complexity was associated with a higher number of YouTube views. CDSongs showed a relatively higher information rate at the beginning and end compared to ADSongs. CDSongs and ADSongs showed a non-uniform information rate, but these periodic oscillatory patterns were more predictable in CDSongs compared to ADSongs. These findings suggest that the optimal balance between predictability and expressivity in information content differs between child- and adult-directed content, but also changes over timescales to potentially support multiple children's needs.