Developmental trajectory of intersubjectivity in the second and third year of life: Study of fixed-population and random-individual effects

Abstract

Colwyn Trevarthen claimed that babies have an intrinsic motivation to communicate and engage with others that he called intersubjectivity. Around the ninth month of life, this motivation changes and passes from person-to-person dyadic (primary intersubjectivity) to triangulate a person–person–object relationship (secondary intersubjectivity). Despite the scientific consensus on this developmental leap, few empirical studies explore the trajectory of this more complex form of intersubjectivity between the second and third year of life. One hundred and fifteen free play sessions from 27 mother–child dyads (13 girls and 14 boys) between 9 and 37 months were filmed and were categorized based on the Level of Intersubjective Attunement Scale. The data were analysed using a linear mixed-effects model. Results show both a population trajectory of the levels of intersubjective attunement and random individual differences. We discuss these results in relation to the binomial typical developmental route and interindividual variability.