Relations between factivity semantics of mental terms and the five-step theory-of-mind scale in Cantonese-speaking children with and without autism spectrum disorders

Background: While considerable research has examined false belief (FB) understanding in children with autism spectrum disorders (ASD), little is known about their other theory-of-mind (ToM) skills. Wellman and Liu (2004) have devised a ToM battery to examine the developmental steps of five ToM skills, including diverse desires (DD), knowledge access (KA), diverse beliefs (DB), contents FB (CFB), and hidden emotion (HE). Based on the finding that strong non-factive mental terms predicted FB understanding in typically developing (TD) children (Cheung et al., 2009), we hypothesize that different mental terms will predict different ToM skills in Cantonese-speaking children with and without ASD. Specifically, we expect that (a) strong non-factive mental terms such as ji5wai4 (“falsely think”) will predict CFB understanding; (b) factive mental terms such as zi1dou6 (“know”) will predict KA; and (c) mental terms that denote emotions, such as hou2hoi1sam1 (“happy”), will predict HE. Objectives: To examine whether knowledge of the factivity semantics of six mental terms, including three factive ones (hou2hoi1sam1 (“happy”), zi1dou6 (“know”), and ng4gei3dak1 (“forget”)) and three strong non-factive ones (ji5wai4 (“falsely think”), ng6wui6 (“mistakenly think”), and waan6soeng2 (“imagine”)), predict the five ToM skills in Wellman and Liu (2004) in Cantonese-speaking children with and without ASD. Methods: 40 Cantonese-speaking children with ASD (mean age = 6.91, SD = 1.47) and 60 TD children matched on language ability (mean age = 6.22, SD = 0.94) participated in this study. A Cantonese version of Wellman and Liu’s (2004) five ToM tasks was used to assess participants’ understanding of the five ToM skills. Knowledge of the factivity semantics of mental terms was evaluated on the basis of participants’ ability to judge the truth/falsity of the complement clauses following factive and strong non-factive mental terms. Participants’ language ability and nonverbal intelligence were measured using the Test of Hong Kong Cantonese Grammar (T’sou et al., 2006) and the Primary Test of Nonverbal Intelligence (Ehrler & McGhee, 2008), respectively. All participants’ scores for language ability and nonverbal intelligence were within the normal range. Results: Hierarchical multiple regressions were conducted to examine the unique contribution of the factivity semantics of mental terms to the five ToM skills. After the effects of age, language ability, and nonverbal intelligence were controlled for, the results showed that autistic children’s understanding of zi1dou6 (“know”) significantly predicted DD and KA, and their understanding of the three strong non-factive mental terms significantly predicted CFB. In TD children, ng4gei3dak1 (“forget”) was found to predict DD and CFB, and hou2hoi1sam1 (“happy”) was found to predict HE. Conclusions: The present study partially confirmed our hypotheses: (a) zi1dou6 (“know”) significantly predicted KA; (b) the three strong nonfactive mental terms significantly predicted CFB in children with ASD; and (c) hou2hoi1sam1 (“happy”) significantly predicted HE in TD children. However, contrary to our hypothesis, ng4gei3dak1 (“forget”) significantly predicted CFB in TD children. These findings suggest that children with ASD rely on knowledge of strong non-factive mental terms for CFB understanding, whereas TD children rely on knowledge of the factive mental term ng4gei3dak1 (“forget”) for CFB understanding.