A clinical assessment tool for advanced theory of mind performance in 5 to 12 year olds.

One hundred forty typically developing 5- to 12-year-old children were assessed with a test of advanced theory of mind employing Happé's strange stories. There was no significant difference in performance between boys and girls. The stories discriminated performance across the different ages with the lowest performance being in the younger children who nevertheless managed to achieve a third of their potential total. However, some of the individual mentalising concepts such as persuasion were too difficult for these younger children. This normative data provides a useful clinical tool to measure mentalising ability in more able children with autism spectrum disorder.