OUTLINING THE WINDOWS OF ACHIEVEMENT OF INTERSUBJECTIVE MILESTONES IN TYPICALLY DEVELOPING TODDLERS.

Babies are born with an innate drive or intrinsic motive formation with which to communicate and share meanings with others and that some authors have called intersubjectivity (S. Bråten & C. Trevarthen, 2007; C. Trevarthen, 1974, 2001). Around the ninth month of life, this motivation changes and passes from a person-to-person dyadic (primary intersubjectivity) to a person-person-object relationship (secondary intersubjectivity). S. Bråten and C. Trevarthen (2007) also proposed a third form or layer of intersubjectivity known as tertiary intersubjectivity. One hundred fifteen free-play sessions of 27 mother-child dyads (13 girls and 14 boys ages 9-37 months) were filmed and categorized using the Level of Intersubjective Attunement Scale (LISA-T; M. Pérez Burriel & M. Sadurní Brugué, 2014; M. Sadurní Brugué & M. Pérez Burriel, 2012). Results from these nine hierarchical levels are presented, following a developmental sequence or population trajectory around an interindividual variability. In this article, we propose viewing these age-related levels as windows of achievement of intersubjective milestones. The statistical analysis suggested a redesign of the LISA-T levels of intersubjectivity; thus, results from this redesign and the debate on the implications of these transitions in infant mental health development are presented.