Developmental continuity in mental state understanding

Background and Objective. Mind understanding is traditionally thought to mature around 4 years of age when children give correct verbal responses to the theory-of-mind-scale tasks (Wellman & Liu, 2004). Recent looking-time paradigms, however, have revealed that infants and toddlers are not blind to others’ minds. Soon after their first year, infants are able to represent intentional and epistemic states in interpreting behaviour (Baillargeon, Scott, & Bian, 2016). Are these early, nonverbal mental state understandings continuous with later, verbal theory-of-mind understandings? In this research, we studied infant understanding of others’ intentional and knowledge states and examined its longitudinal connections with their theory - of-mind competencies at age 4.
Methodology. One hundred and twelve 16-month-olds (M_age = 15 months 24 days; 63 boys) participated in the intentional understanding test. We used Phillips et al. (2002) paradigm to measure infants’ ability to use an actress’s facial-vocal expression to infer her intention towards a target object. Sixty-two of them were retested at age 4 (M_age = 48 months 24 days; 28 boys) with a theory-of-mind scale (Wellman & Liu, 2004). The scale includes five items, testing young children’s understandings of diverse desires, knowledge access, diverse beliefs, false belief, and hidden emotion. Another group of 58 16-month-olds (M_age = 15 months 25 days; 27 boys) participated in the epistemic understanding test. We used Luo & Baillargeon (2007) paradigm to assess infants’ ability to consider an actress’s knowledge about the scene to predict her subsequent action. Thirty-two of them (M_age= 47 months 26 days; 15 boys) were retested on the same five-item theory-of-mind scale.
Results and Discussion. In the intentional understanding test, the infants looked reliably longer in the inconsistent than consistent test events. We took the looking time difference between inconsistent and consistent test events as infants’ intentional understanding and correlated it with later theory-of-mind performances. Results indicated that infant intentional understanding significantly predicted later understanding of diverse desires (r= .42, p < .01), but not the overall theory-of-mind score. This longitudinal association remained significant even when non-verbal IQ, language ability, and executive function were accounted for. In the epistemic understanding test, the infants looked equally at the new and old goal test events. Infant representation of others’ knowledge state significantly predicted performances in the knowledge-access item in the theory-of-mind scale at 4 years (r = .47, p < .01), but not its overall score. Again, this longitudinal relationship remained significant after the effects of IQ, verbal competence, and executive function were controlled. Taken together, our findings suggest a social-cognitive continuity of representing mental states. Copyright © 2017 AVANT.