Mothers' use of cognitive state verbs in picture-book reading and the development of children's understanding of mind: a longitudinal study.

Mothers read stories to their children (N=41) aged between 3.3 years and 5.11 years old, and children then completed two false-belief tasks. One year later, mothers read a story to 37 of those children who were also given four tasks to assess their advanced understanding of mental states. Mothers' early use of cognitive verbs in picture-book reading correlated with their children's later understanding of mental states. Some pragmatic aspects of maternal input correlated with children's later outcomes. Two different factors in mothers' cognitive discourse were identified, suggesting a zone of proximal development in children's understanding of mental states.