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Theory of Mind (ToM) is the ability to infer others’ mental states and thus to predict their behavior (Perner, 1991). Therefore, ToM is essential for the adequate adjustment of behavior in social situations. ToM can be divided into: 1) cognitive ToM encompassing inferences about intentions and beliefs and 2) affective ToM encompassing inferences about emotions (Shamay-Tsoory, Harari, Aharon-Peretz, & Levkovitz, 2010). Well-functioning skills of both ToM aspects are much-needed in the developmental period of adolescence because in this age phase peer relationships become more important and romantic relationships arise (Steinberg & Morris, 2001). Importantly, affective psychopathological disorders often have their onset in adolescence. ToM development in adolescence might be based on underlying cognitive mechanisms such as the ability to inhibit one’s own thoughts in order to understand another person’s thoughts (Carlson & Moses, 2001). Another possible mechanism relates to functional brain development across adolescence (Blakemore, 2008). Therefore, neurocognitive mechanisms may underlie ongoing ToM development in adolescence. First studies indicate an ongoing behavioral and functional brain development of ToM (e.g. Blakemore, 2008). However, ToM development in adolescence and how this might relate to underlying (neuro)cognitive functions remains largely underexamined. The major aims of the current thesis were first to answer the overall question whether there is an ongoing development of ToM in adolescence. This question relates to both behavioral and functional brain development. As a second major aim, the present work sought to elucidate possible (neuro)cognitive mechanisms of ongoing ToM development across adolescence. Specifically, these cognitive mechanisms might be basic cognitive functions as well as executive functions. Additionally, the present work aimed at exploring potential (neuro)cognitive mechanisms through an integration of both behavioral and functional brain studies. The current experimental work spans three cross-sectional studies investigating adolescents (aged around 12-15 years) and young adults (aged around 18-22 years) to examine for the first time both the behavioral (studies I and II) and functional brain development of ToM (study III) in adolescence and its underlying (neuro)cognitive mechanisms. In all three studies, more complex, advanced ToM tasks were employed to avoid ceiling effects. Study I was aimed at investigating if cognitive and affective ToM continues to develop in adolescence and at exploring if basic cognitive variables such as verbal ability, speed of processing, and working memory capacity underlie such development. Hence, two groups of adolescents and young adults completed tasks of ToM and basic cognitive abilities. Large age effects were revealed on both measures of ToM: adolescents performed lower than adults. These age differences remained significant after controlling for basic cognitive variables. However, verbal ability covaried with performance in affective ToM. Overall, results support the hypothesis of an ongoing development of ToM from adolescence to adulthood on both cognitive and affective aspects. Results may further indicate verbal ability being a basic cognitive mechanism of affective ToM. Study II was designed to further explore if affective ToM, as measured with a dynamic realistic task, continues to develop across adolescence. Importantly, this study sought to explore executive functions as higher cognitive mechanisms of developing affective ToM across adolescence. A large group spanning adolescents and young adults evaluated affective mental states depicted by actors in video clips. Additionally, participants were examined with three subcomponents of executive functions, inhibition, updating, and shifting following the classification of Miyake et al. (2000). Affective ToM performance was positively related to age and all three executive functions. Specifically, inhibition explained the largest amount of variance in age related differences of affective ToM performance. Overall, these results indicate the importance of inhibition as key underlying mechanism of developing an advanced affective ToM in adolescence. Study III set out to explore the functional brain development of affective ToM in adolescence by using functional magnetic resonance imaging (fMRI). The affective ToM measure was the behavioral developmentally sensitive task from study II. An additional control condition consisted of the same emotional stimuli with the instruction to focus on physical information. This study faced methodical challenges of developmental fMRI studies by matching performance of groups. The ventromedial prefrontal cortex (vMPFC) was significantly less deactivated in adolescents in comparison to adults, which might suggest that adolescents seem to rely more on self-referential processes for affective ToM. Furthermore, adolescents compared to adults showed greater activation in the dorsolateral prefrontal cortex (DLPFC) in the control condition, indicating that adolescents might be distracted by the emotional content and therefore needed to focus more on the physical content of the stimulus. These findings suggest affective ToM continues to develop on the functional brain level and reveals different underlying neurocognitive strategies for adolescents in contrast to adults. In summary, the current thesis investigated whether ToM continues to develop in adolescence until young adulthood and explored underlying (neuro)cognitive mechanisms. Findings suggest that there is indeed an ongoing development of both the cognitive and affective aspect of ToM, which importantly contributes to the conceptual debate. Moreover, the second benefit to the debate is to demonstrate how this change may occur. As a basic cognitive mechanism verbal ability and as an executive functioning mechanism inhibition was revealed. Furthermore, neurocognitive mechanisms in form of different underlying neurocognitive strategies of adolescents compared to adults were shown. Taken together, ToM development in adolescence seems to mirror a different adaptive cognitive style in adolescence (Crone & Dahl, 2012). This seems to be important for solving the wealth of socio-emotional developmental tasks that are relevant for this age span.

Theory of Mind (ToM) is the ability to infer others’ mental states and thus to predict their behavior (Perner, 1991). Therefore, ToM is essential for the adequate adjustment of behavior in social situations. ToM can be divided into: 1) cognitive ToM encompassing inferences about intentions and beliefs and 2) affective ToM encompassing inferences about emotions (Shamay-Tsoory, Harari, Aharon-Peretz, & Levkovitz, 2010). Well-functioning skills of both ToM aspects are much-needed in the developmental period of adolescence because in this age phase peer relationships become more important and romantic relationships arise (Steinberg & Morris, 2001). Importantly, affective psychopathological disorders often have their onset in adolescence. ToM development in adolescence might be based on underlying cognitive mechanisms such as the ability to inhibit one’s own thoughts in order to understand another person’s thoughts (Carlson & Moses, 2001). Another possible mechanism relates to functional brain development across adolescence (Blakemore, 2008). Therefore, neurocognitive mechanisms may underlie ongoing ToM development in adolescence. First studies indicate an ongoing behavioral and functional brain development of ToM (e.g. Blakemore, 2008). However, ToM development in adolescence and how this might relate to underlying (neuro)cognitive functions remains largely underexamined. The major aims of the current thesis were first to answer the overall question whether there is an ongoing development of ToM in adolescence. This question relates to both behavioral and functional brain development. As a second major aim, the present work sought to elucidate possible (neuro)cognitive mechanisms of ongoing ToM development across adolescence. Specifically, these cognitive mechanisms might be basic cognitive functions as well as executive functions. Additionally, the present work aimed at exploring potential (neuro)cognitive mechanisms through an integration of both behavioral and functional brain studies. The current experimental work spans three cross-sectional studies investigating adolescents (aged around 12-15 years) and young adults (aged around 18-22 years) to examine for the first time both the behavioral (studies I and II) and functional brain development of ToM (study III) in adolescence and its underlying (neuro)cognitive mechanisms. In all three studies, more complex, advanced ToM tasks were employed to avoid ceiling effects. Study I was aimed at investigating if cognitive and affective ToM continues to develop in adolescence and at exploring if basic cognitive variables such as verbal ability, speed of processing, and working memory capacity underlie such development. Hence, two groups of adolescents and young adults completed tasks of ToM and basic cognitive abilities. Large age effects were revealed on both measures of ToM: adolescents performed lower than adults. These age differences remained significant after controlling for basic cognitive variables. However, verbal ability covaried with performance in affective ToM. Overall, results support the hypothesis of an ongoing development of ToM from adolescence to adulthood on both cognitive and affective aspects. Results may further indicate verbal ability being a basic cognitive mechanism of affective ToM. Study II was designed to further explore if affective ToM, as measured with a dynamic realistic task, continues to develop across adolescence. Importantly, this study sought to explore executive functions as higher cognitive mechanisms of developing affective ToM across adolescence. A large group spanning adolescents and young adults evaluated affective mental states depicted by actors in video clips. Additionally, participants were examined with three subcomponents of executive functions, inhibition, updating, and shifting following the classification of Miyake et al. (2000). Affective ToM performance was positively related to age and all three executive functions. Specifically, inhibition explained the largest amount of variance in age related differences of affective ToM performance. Overall, these results indicate the importance of inhibition as key underlying mechanism of developing an advanced affective ToM in adolescence. Study III set out to explore the functional brain development of affective ToM in adolescence by using functional magnetic resonance imaging (fMRI). The affective ToM measure was the behavioral developmentally sensitive task from study II. An additional control condition consisted of the same emotional stimuli with the instruction to focus on physical information. This study faced methodical challenges of developmental fMRI studies by matching performance of groups. The ventromedial prefrontal cortex (vMPFC) was significantly less deactivated in adolescents in comparison to adults, which might suggest that adolescents seem to rely more on self-referential processes for affective ToM. Furthermore, adolescents compared to adults showed greater activation in the dorsolateral prefrontal cortex (DLPFC) in the control condition, indicating that adolescents might be distracted by the emotional content and therefore needed to focus more on the physical content of the stimulus. These findings suggest affective ToM continues to develop on the functional brain level and reveals different underlying neurocognitive strategies for adolescents in contrast to adults. In summary, the current thesis investigated whether ToM continues to develop in adolescence until young adulthood and explored underlying (neuro)cognitive mechanisms. Findings suggest that there is indeed an ongoing development of both the cognitive and affective aspect of ToM, which importantly contributes to the conceptual debate. Moreover, the second benefit to the debate is to demonstrate how this change may occur. As a basic cognitive mechanism verbal ability and as an executive functioning mechanism inhibition was revealed. Furthermore, neurocognitive mechanisms in form of different underlying neurocognitive strategies of adolescents compared to adults were shown. Taken together, ToM development in adolescence seems to mirror a different adaptive cognitive style in adolescence (Crone & Dahl, 2012). This seems to be important for solving the wealth of socio-emotional developmental tasks that are relevant for this age span.:Abstract 1 1 General Introduction 4 1.1 Concept of ToM: cognitive and affective aspects 7 1.2 ToM Development 8 1.2.1 ToM Development until Adolescence 9 1.2.2 ToM Development in Adolescence 12 1.3 Cognitive Mechanisms 14 1.3.1 Basic Cognitive Functions 15 1.3.2 Executive Functions 17 1.4 Neurocognitive Mechanisms 19 1.4.1 Functional brain development of ToM 20 1.4.2 Integrating behavioral and functional brain studies 21 2 Outline and Central Questions 24 2.1 Does ToM continue to develop in adolescence? 24 2.1.1 Does ToM continue to develop on the behavioral level? 24 2.1.2 Does ToM continue to develop on the level of brain function? 25 2.2 What are (neuro)cognitive mechanisms of ToM development in adolescence? 26 2.2.1 What are basic cognitive and executive functioning mechanisms? 26 2.2.2 Can mechanisms be concluded from the integration of behavioral data and functional brain processes? 26 3 Study I – ToM Development in Adolescence and its Basic Cognitive Mechanisms 28 3.1 Introduction 28 3.2 Method 32 3.2.1 Participants 32 3.2.2 Materials 33 3.3 Results 36 3.3.1 Age Effects 36 3.3.2 Influence of puberty on social cognition 37 3.3.3 Controlling for Basic Cognitive Abilities 39 3.4 Discussion 40 3.4.1 Overview 40 3.4.2 Age differences in social cognition 40 3.4.3 Influence of puberty on social cognition 42 3.4.4 Covariates of age differences in social cognition 42 3.4.5 Conclusions 43 4 Study II – ToM Development in Adolescence and its Executive Functioning Mechanisms 45 4.1 Introduction 45 4.2 Method 49 4.2.1 Participants 49 4.2.2 Materials 49 4.3 Results 52 4.3.1 Decomposing the Age Effect in Affective Theory of Mind 54 4.4 Discussion 55 4.4.1 Overview 55 4.4.2 Conclusions 57 5 Study III – ToM Development in Adolescence and its Neurocognitive Mechanisms 59 5.1 Introduction 59 5.2 Method 61 5.2.1 Participants 61 5.2.2 Stimuli, design and procedure 62 5.2.3 Statistical analysis of behavioral data 65 5.2.4 Functional imaging 65 5.2.5 Statistical analysis of fMRI data 66 5.3 Results 67 5.3.1 Behavioral results 67 5.3.2 fMRI results 68 5.4 Discussion 71 5.4.1 Developmental differences in brain activations 71 5.4.2 Conclusions 74 6 General Discussion 75 6.1 Summary of empirical findings 75 6.2 Discussion and integration of the main empirical findings 76 6.2.1 Continued ToM development in adolescence 76 6.2.2 (Neuro)cognitive mechanisms of ToM development in adolescence 80 6.3 Implications and outlook 89 6.3.1 Current findings and their conceptual fit to present models of ToM 90 6.3.2 Underpinning the concept of cognitive and affective ToM 91 6.3.3 Conceptual and methodical implications of performance matching 92 6.3.4 The role of puberty on ToM 94 6.3.5 Predicting other’s economic behavior 95 6.3.6 Structural brain development 96 6.3.7 Applied perspective 97 6.4 Summary 98 References 99