Concurrent Validity Evidence Supporting the Theory of Mind Inventory

Background: Theory of Mind abilities are a well-known challenge for individuals with autism spectrum disorder (ASD). Assessing Theory of Mind abilities with standard behavioral tasks can be problematic, due to language constraints and the binary nature of most task responses. To address these limitations, the Theory of Mind Inventory (ToMI) was designed as a caregiver report measure, in which caregivers rate their child’s theory of mind abilities using a graphic rating scale (Hutchins et al., 2010). Assessed behaviors range from early-emerging behaviors (e.g., joint attention, emotion recognition) through later-emerging behaviors (e.g., understanding sarcasm, understanding second-order false beliefs). Strong correlations between ToMI scores and measures of social impairment in adolescents with ASD support the ToMI’s use in this population (Lerner et al., 2011). However, this concurrent validity evidence was limited in three ways: 1) data was only gathered in adolescents; 2) ASD diagnoses were not confirmed through a gold-standard diagnostic assessment; and 3) no evidence was collected in controls.

Objectives: To provide concurrent validity evidence for using the ToMI with children with and without ASD.

Methods:  To determine eligibility for a larger study, parents of 20 children with ASD (4;0-6;7) and 20 children with typical development (TD, 3;1-6;5), matched for verbal ability and gender, completed a series of interviews and questionnaires: the Vineland Adaptive Behavior Scales-Second Edition (Vineland-2; Sparrow et al., 2005); the Social Responsiveness Scale-Second Edition (SRS-2; Constantino & Gruber, 2012) and the ToMI. Parents of children with ASD also completed the Autism Diagnostic Interview-Revised (Lord et al., 1994) to confirm ASD diagnoses. Pearson product moment correlations (r) were calculated between the ToMI Composite score and the following: Vineland-2 Communication and Socialization subscales scores and the SRS-2 Total score and Social-Communication Index. Correlations were calculated for the combined sample and for each group separately.

Results:  In the combined sample (ASD + TD), the ToMI composite score was found to correlate highly with Vineland-2 Communication (r=.59, p<.001) and Socialization (r=.64, p<.001) subscale scores as well as the SRS-2 Total score (r=-.68, p<.001) and Social Communication Index (r=-.68, p<.001). When analyzed as separate groups, correlations remained for the ASD group and, to a lesser extent, for the TD group. In the ASD group, the ToMI Composite score was correlated with the Vineland-2 Communication (r=.45, p=.049) and Socialization (r=.59, p=.006) subscales as well as the SRS-2 Total score (r=-.48, p=.032) and Social Communication Index (r=-.49, p=.030). In contrast, within the TD sample, ToMI composite scores were only significantly correlated with the Vineland-2 Communication scores (r=.54, p=.015).

Conclusions: The accumulated evidence supports the concurrent validity of the Theory of Mind Inventory. In the present sample, correlations were especially strong when ASD and TD groups were combined, likely due to the increased representation of data points across the spectrum of possible scores. Yet, even when groups were examined individually, some correlations remained high. Overall, evidence supports the ToMI's use as a valid indicator of target social and communication skills.