DEVELOPMENT OF LAUGHTER AND PROTOPHONES IN THEIR COMPLEXITY IN FORM AND FUNCTION

Early development includes vocalizations that play a key role in language, i.e., laughter and protophones
(pre-linguistic vocalizations). Laughter is an important communicative tool which appears after a few
months of life (Ruch & Ekman, 2001), and which, later, will be daily used within conversations (Vettin &
Todt, 2004). Just as language, it evolves over time from a primal form (Kret et al., 2021). In adults, it is
coordinated with speech as it does not occur randomly in the middle of sentences, but punctuates
speech (Provine, 1993). Protophones are considered to be the precursors to speech since they follow
developmental phases leading to more refined speech-like sounds (Nathani, et al. 2006). In addition, any
upheaval of this pattern usually causes future language disorders (Oller et al., 1999). Interestingly, no
studies examined how infants start to coordinate laughter with protophones nor whether the complexity
in form of these vocalisations evolves concurrently as their complexity in function.
This project aims to study the complexity of protophones and laughter in both the form and function,
across cultural and age groups. The first aim is to examine the acoustic form of laughter and
protophones with traditional acoustic analyses and to test for commonalities and differences in their
development. The second aim is to examine in which behavioural and emotional contexts these
vocalizations occur and co-occur and to what extent there may be changes in their ontogeny. I
hypothesize that laughter variation in both form and function becomes reshaped when starting to be
coordinated with protophones.