Assessing Theory of Mind and Its Relationship to ASD Symptom Severity

Background: Theory of mind (ToM) has long been studied as a core weakness in autism spectrum disorder (ASD; Tager-Flusberg, 2007) due to its relationship with social and emotional reciprocity, a core symptom of ASD. The literature indicates that better ToM is associated with higher cognitive functioning and less severe social deficit in ASD (Livingston et al., 2018; Happe, 2015). ToM has been explored as a focus of intervention, but there has been limited evidence that these interventions are effective, partly due to limited outcome measures (Fletcher-Watson, McConnell, Manola & McConachie, 2014). Tasks that measure ToM tend to vary greatly between studies, are lengthy, and require significant training to administer. The NEPSY-II ToM subtest is a relatively new standardized measure of ToM skills that can be used in the assessment of children with and without ASD. Furthermore, while ToM abilities have been compared to measures of ASD symptom severity such as the Social Responsiveness Scale, they have not been compared to the recently released ADOS-2 Comparison score. Due to the high applicability and use of both of these measures, the relationship between ASD severity, as measured by the ADOS-2 Comparison Score, and ToM, as measured by the NEPSY-II, is important to examine.

Objectives: This study evaluates the relationships between ToM as measured by the NEPSY-II and ASD symptom severity, as measured by the ADOS-2 Comparison Score. We hypothesize that ToM skills will predict ASD symptom severity above and beyond cognitive abilities.

Methods: Children with ASD, ages 6-12, with a full scale IQ (FSIQ) score above 50, were assessed with the Stanford-Binet Intelligence Test, 5^th Edition, the social perception subtests of the NEPSY-II and the ADOS-2. ToM was regressed onto the ADOS-2 comparison score after controlling for FSIQ.

Results: Fifty-two children (43 males, 9 females) with ASD, a mean age of 9.6 (SD = 1.9), and a mean FSIQ of 92.79 (SD = 19.53, range: 51-126) participated in the study. All participants completed Module 3 of the ADOS-2. FSIQ was a significant predictor of the ADOS-2 comparison score, r = 0.32, F(1, 49) = 5.73, p = 0.02, predicting 10.5% of the variance. Together, FSIQ and ToM predicted 24% of the variance, r = 0.52, F(2, 48) = 8.90, p = 0.001 with ToM accounting for significantly more variance, R² Change = 0.17, F(1, 48) = 10.9, p = 0.002.

Conclusions: Theory of Mind skills significantly predicted ASD symptom severity, even when controlling for overall IQ. These results suggest that ToM is associated with ASD symptoms, even when accounting for broad differences in cognitive functioning. Given the age range of our sample and the relative stability of their IQ, this highlights the impact ToM skill training may have for school-age children with ASD. While ToM interventions that use visual aids show promise (Paynter & Peter, 2013), many studies have mixed results due to limitations in outcome measures. Our results support the use of the NEPSY-II ToM assessment in ASD research and clinical practice, as a brief, standardized, easy-to-administer measure of ToM.