The Lausanne Trilogue Play (LTP) is a widely used laboratory situation designed for the systematic observation of mother-father-infant interactions for clinical and research purposes. Nevertheless, its ecological validity has never been tested. In this exploratory study, 49 primiparous parents with their 3-month-old infants were assessed by questionnaires to determine the extent to which their behaviour in the LTP was typical, that is, representative of everyday interactions. Results show that (a) most of the parents assessed their behaviour as typical and (b) the quality of triadic interactions was linked with parents’ assessment of the typicality of the infant’s behaviour. © 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group.