Advanced theory of mind in children with mild intellectual disability and deaf or hard of hearing children: A two-year longitudinal study in middle childhood.

The present study investigates the development of advanced theory of mind (AToM) among typically developing (TD) children, children with mild intellectual disability (MID), and deaf or hard of hearing (DHH) children. The 2-year longitudinal study comprised three waves and included a large sample of children from Poland in middle childhood aged around 7.5-9.5 years (N = 779; M = 7.7, SD = 0.92 at wave 1). The analysis of children's understanding of second-order false belief and the Faux-Pas Recognition Test showed that TD children outperformed children with MID and DHH children on both measures. At 7.5 years, almost 60% of the TD children correctly solved the second-order false belief task; correct performance at 7.5 years in children with MID and DHH children was 27 and 38% respectively. Two years later, correct performance rose to 80% (TD children), 45% (children with MID), and 63% (DHH children). Despite these differences, the speed of AToM development did not differ across the groups. The development of faux-pas recognition followed a non-linear pattern, with TD children showing no further significant development after mid-elementary school. Our findings show differences in AToM development between TD children, children with MID, and DHH children, and they suggest that children's development of AToM may follow different developmental pathways, depending on the aspect of AToM under study.