Language complexity modulates 8- and 10-year-olds' success at using their theory of mind abilities in a communication task.

Basic competence in theory of mind is acquired during early childhood. Nonetheless, evidence suggests that the ability to take others' perspectives in communication improves continuously from middle childhood to the late teenage years. This indicates that theory of mind performance undergoes protracted developmental changes after the acquisition of basic competence. Currently, little is known about the factors that constrain children's performance or that contribute to age-related improvement. A sample of 39 8-year-olds and 56 10-year-olds were tested on a communication task in which a speaker's limited perspective needed to be taken into account and the complexity of the speaker's utterance varied. Our findings showed that 10-year-olds were generally less egocentric than 8-year-olds. Children of both ages committed more egocentric errors when a speaker uttered complex sentences compared with simple sentences. Both 8- and 10-year-olds were affected by the demand to integrate complex sentences with the speaker's limited perspective and to a similar degree. These results suggest that long after children's development of simple visual perspective-taking, their use of this ability to assist communication is substantially constrained by the complexity of the language involved.