The Emergence of Theory of Mind: Cognitive and Neural Basis of False Belief Understanding in Preschool Age

Human social interaction crucially depends on the ability to attribute thoughts and beliefs to other individuals. This ability is referred to as Theory of Mind (ToM), and understanding that other people can have false beliefs about the world is considered to be a critical test of ToM. In childhood, a developmental breakthrough is achieved around the age of 4 years, when children start explicitly reasoning about others’ false beliefs. The cognitive and neural developments that lead to this milestone of human cognition, however, are currently unknown. Moreover, recently, novel im- plicit paradigms have shown that, already before the age of 2 years, infants display correct expectations of the actions of an agent with a false belief. The processes that underlie these expectations and their relation to the later-developing explicit false belief reasoning, however, are unclear. The current thesis addresses these open issues in three studies. The first study investigates the developmental trajectory and robustness of an implicit false belief task longitudinally from the age of 2 to 4 years. We find that children only perform above chance by the age of 4 years, but not at 2 and 3 years. This indicates that early success on implicit false belief tasks is fragile. The second study examines the correlation of implicit and explicit false belief tasks with each other and with co-developing cognitive abilities. This shows a dissociation of implicit and explicit false belief tasks in that performance on the two task types does not correlate, and that explicit false belief tasks correlate with syntactic and executive functions, whereas implicit false be- lief tasks do not. Finally, the third study shows that the maturation of white matter in brain regions that support false belief reasoning in adultsand of their dorsal connectivity to the inferior frontal gyrus, suggested to support hierarchical processing, is associated with the emergence of explicit false belief reasoning in 3- and 4-year-old children. These associations are independent of implicit false belief-related action anticipation and of developments in other cognitive domains. Taken together, our results speak for a dissociation of the processes underlying implicit and explicit false belief tasks. We suggest that the developmental breakthrough in explicit false belief reasoning around the age of 4 years might result from improved belief processing, emerging hierarchical processing abilities, and the maturation of the connection between the relevant brain regions. Furthermore, I speculate on processes that might underlie early success on implicit false belief tasks in infancy.:Acknowledgements iii Summary xi Deutsche Zusammenfassung xvii 1 General Introduction 1.1 Theory of Mind . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1.1 Precursors of ToM in Infancy . . . . . . . . . . . . . 3 1.1.2 False Belief Understanding . . . . . . . . . . . . . . . 4 1.1.3 Relation between Implicit and Explicit False Belief Tasks . . . . . . . 8 1.1.4 Theoretical Accounts of the Emergence of ToM . . . 14 1.2 Relation to Other Cognitive Domains . . . . . . . . . . . . . 20 1.2.1 Executive Function . . . . . . . . . . . . . . . . . . . 25 1.2.2 Language . . . . . . . . . . . . . . . . . . . . . . . . 26 1.2.3 Correlations with Implicit False Belief Tasks . . . . . 29 1.3 Neural Basis of ToM . . . . . . . . . . . . . . . . . . . . . . 31 1.3.1 Neural Basis of ToM in Adults . . . . . . . . . . . . . 31 1.3.2 Neural Basis of ToM in Development . . . . . . . . . 35 1.3.3 Structural Brain Development in Early Childhood . . 36 1.4 Research Questions and Hypotheses . . . . . . . . . . . . . . 38 2 Study 1: Longitudinal evidence for 4-year-olds’ but not 2- and 3-year-olds’ false belief-related action anticipation . . . . . . . . . . . .45 3 Study 2: Implicit and explicit false belief development in preschool children . . . . . . . . . . . .73 4 Study 3: White matter maturation is associated with the emergence of Theory of Mind in early childhood . . . . . . . . . . . .91 5 General Discussion 5.1 Is there a continuity from early-developing to later explicit false belief abilities? . . . . . . . . . . . . . . . . . . . . . . . 106 5.2 What is the relation of implicit and explicit false belief tasks to other cognitive domains? . . . . . . . . . . . . . . . . . . 109 5.3 What is the neural basis of the emergence of ToM? And what does this tell us about the underlying cognitive processes? . . . . 114 5.4 What processes underlie implicit false belief tasks?. . . . . 118 5.5 Future Research and Limitations . . . . . . . . . . . . . . . 120 5.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 References . . . . . . . 128 A Supplements Study 1 . . . . . . . 161 B Supplements Study 2 . . . . . . . 163 C Supplements Study 3 . . . . . . . .181 Abbreviations . . . . . . . . 187 List of Figures . . . . . . . . 191 List of Tables . . . . . . . . 19