THE DEVELOPMENT OF SHYNESS FROM CHILDHOOD TO ADULTHOOD: SUBTYPES, BIOLOGICAL MECHANISMS, CORRELATES, AND OUTCOMES

Abstract

Shyness is a personality trait that is stable across time and situations in some individuals. While childhood shyness is a risk factor for later mental health and emotional problems, not all shy children grow up to have these problems. This thesis examined subtypes of shyness identified based on the temporal stability of shyness and based on levels of sociability and their corresponding outcomes, as well as the roles of social and biological contextual factors. Chapters 2-4 comprise the empirical studies. In Chapter 2, I report three shyness trajectories from middle childhood to adulthood (ages 8 to 30-35). Relative to a low-stable non-shy trajectory, children with an increasing, but not a decreasing, shy trajectory were at higher risk for clinically significant social anxiety, depression, and substance use, and were hypervigilant to angry faces in adulthood. Chapters 3 and 4 then report electrocortical correlates and mechanisms during the processing of non-social auditory novelty and social exclusion across children, adolescents, and adults with varying levels of shyness and sociability. Chapter 3 established that shyness, but not sociability, was related to the P300 ERP in processing non-social auditory stimuli in both 10-year-old children and adults, in support of the notion that shyness and sociability are independent personality dimensions. Findings on subtypes of shyness also showed that children characterized by conflicted shyness (with high levels of both shyness and sociability) reported higher neuroticism, but this relation was mediated by increased P300 amplitudes to processing background stimuli. Finally, Chapter 4 reports that individuals characterized by conflicted shyness who exhibited high theta EEG spectral power to social exclusion were most fearful of negative evaluation, irrespective of age. Also, conflicted shy adolescents who showed high theta spectral power to social exclusion were most likely to engage in substance-use. These findings highlight that there is much heterogeneity in shyness, and that shyness is not directly related to adverse mental health outcomes.