The Comprehensive Assessment of Theory of Mind (CAT): A Novel Measure of 3- to 8-Year-Old Children's Theory of Mind and an Evaluation of Mental-State Scaling.

This study describes a novel measure of children's Theory of Mind (ToM) development-called the Comprehensive Assessment of ToM (CAT)-that addresses limitations in existing ToM measures. This behavioral measure includes three-six items each about diverse desires, diverse beliefs, knowledge access, knowledge expertise, false belief, and visual perspective taking, as well as nonsocial representational reasoning (i.e., false-sign). All items include a prediction, explanation, and general comprehension question. The measure is psychometrically valid and robust in 3- to 8-year-old children (n = 206; 104 boys; 101 girls; 1 gender fluid; 37.7% White non-Hispanic). Children's performance replicates prior findings with the commonly used Wellman and Liu (2004) ToM scale, but also reveals a novel and nuanced pattern of mental-state scaling over early to middle childhood.