Developmental relationships between production and comprehension of mental terms

Mental terms, including belief and desire terms, were studied in a sample of 14 mother-child pairs longitudinally when the children were 2;0, 3;0, and 4;0 in order to examine the acquisition of these terms. Percentage use of utterances involving belief and desire terms in naturalistic interactions were calculated for each subject. In addition, children at 4;0 were tested for comprehension of the distinctions between the belief terms know, think and guess, using a task designed to assess the understanding of the expression of relative certainty. Results showed an interlocking of mothers' use of belief terms, children's use of desire and belief terms, and children's comprehension of belief terms. Children's use of desire terms at 2;0 was related to their use of belief terms at 3;0 and their comprehension of belief terms at 4;0, perhaps reflecting their developing theory of mind. Maternal use of belief terms when their children were 2;0 was significantly related to their children's concurrent use of desire terms, and significantly predicted their children's use of belief terms both one and two years later. Mothers' use of belief terms at 2;0 also predicted their children's comprehension of belief terms at 4;0. These results are consistent with a picture of maternal linguistic scaffolding of their children's developing theory of mind.