66

The goal of this retrospective and longitudinal study is to compare the early development of prosodic interactions between the parent and typically developing child (n = 13) and between the parent and child later diagnosed with autism (n = 11). This study is based on an acoustic analysis of family home movies filmed during the child’s first year of life. Durations of engagement and disengagement phases as well as response latencies have been measured. The results show comparable trajectories before the age of seven months, whereas differences appear between groups after the age of eight months. Thus, a better understanding of the development of autism spectrum disorder will encourage early screening and therefore starting treatment earlier.