Self-awareness moderates the relation between maternal mental state language about desires and children's mental state vocabulary.

In this intervention study, we tested the differential effect of talking about children's desires versus talking about others' thoughts and knowledge on children's acquisition of mental state vocabulary for children who did and did not have mirror self-recognition. In a sample of 96 mother-toddler dyads, each mother was randomly assigned a specially constructed, interactive lift-the-flap book to read to her child three times a week for 4 weeks. In the child desire condition the story elicited comments regarding the child's desires, and in the cognitive condition the story elicited the mother's comments about her own thoughts and knowledge while reading the story. Children's mirror self-recognition and mental state vocabulary were assessed at pre- and post-test. Children in the condition that focused on the child's desires showed a significantly greater increase in their mental state vocabulary; however, this effect was moderated by their levels of self-awareness, with children benefitting more from the intervention if they also showed self-recognition at pre-test. We argue that the combination of specific types of maternal talk and children's prior insights facilitates gains in children's mental state vocabulary.