The Lausanne Trilogue Play: bringing together developmental and systemic perspectives in clinical settings.

Developmentalists have demonstrated that the quality of relationships established by infants with their proximal social environment is crucial for lifecourse development. However, studies of parent–infant relationships have mostly centred on the mother–child dyad. Stemming from family systems theory that considers interactions within the whole family as critical for an individual's personal development, a group of family therapists and researchers in Lausanne (Switzerland) tried to bridge the gap between systemic and developmental thinking by stressing the need to establish the mother–father–infant triad as a collective unit of study. In response, they created the Lausanne Trilogue Play (LTP), a method to systematically assess the quality of mother–father–infant interactions. The LTP is an observational situation during which parents are asked to play with their infant in four parts: (i) one parent plays with the infant, while the other parent is 'simply present'; (ii) the parents switch roles; (iii) all three play together; (iv) the parents discuss in front of the infant. The theoretical model underpinning the LTP is the family alliance model, which postulates that the quality of the coordination demonstrated by the triad to achieve this task can be assessed mainly through careful observation of non‐verbal behaviours as indicators of the achievement of four interactive functions (i.e., participation, organisation, focalisation, affect sharing); fulfilment of these functions determines the quality of relational functioning within the system. This article introduces the clinical, theoretical, and empirical foundations of using the LTP method with the family alliance model; its use in clinical and research contexts; and the most recent advances in the field of research on mother–father–infant interactions based on the LTP situation. [ABSTRACT FROM AUTHOR]