Differential Susceptibility to Social Contexts: Putting "For Better and For Worse" to the test

The differential susceptibility model asserts that individuals vary in their general susceptibility to environmental influences.Crucially, the very children that are disproportionately vulnerable to harsh and low-quality parenting, may benefit disproportionately from supportive and high-quality parenting, being susceptible “for better and for worse”. While differential susceptibility offers an exciting new perspective on human development, many unanswered questions remain. This dissertation addresses some of these questions, guided by four aims. These aims were studied using samples varying in age from infancy to adulthood, and employing longitudinal, meta-analytic, experimental, and observational methods. The first and overarching aim of this dissertation was to examine whether individuals vary in their susceptibility to social contexts, particularly parenting, both “for better” and “for worse”, depending on their temperament traits. Through meta-analysis it was found that children with a more difficult temperament (compared to those with an easier temperament) and infants high on negative emotionality were more vulnerable to negative parenting, but also profited more from positive parenting, supporting the differential susceptibility model. Additional longitudinal studies showed that children higher on sensory processing sensitivity and parents higher on openness seemed more susceptible to environmental influences. Yet three studies in this dissertation did not find support for differential susceptibility. Moreover, to test whether the same children can be susceptible to both negative and positive social contexts, within-person designs are needed. Two studies, a within-person experiment and observations, found mixed support for this assumption of differential susceptibility. The findings in this dissertation indicate that it is challenging to find individuals who are susceptible to both harsh and supportive environments. Moreover, susceptible individuals will likely be found under specific conditions, depending on the markers used to identify them, the age at which they are studied, and the time scale at which they are studied. The second aim was to test existing markers and find new markers that can be used to tell which individuals would be more and less susceptible to environmental influences. While negative emotionality during infancy may be used to recognize more and less susceptible individuals, sensory processing sensitivity and openness may be better used to this end after infancy. Surgency and effortful control are less likely to function as general susceptibility markers, although they may pick up on more domain-specific sensitivity to parenting. The third aim was to examine whether differences in susceptibility exist throughout the lifespan, and whether the best temperament traits to identify these differences vary throughout life. Support for individual differences in susceptibility was found among children of different ages, as well as adults, suggesting that susceptibility is either a characteristic that remains stable throughout life, or that multiple windows of plasticity exist, beyond infancy. The fourth aim was to examine both differential susceptibility (focusing on long-term developmental changes) and differential reactivity (focusing on short-term changes), and their association. While support for both differential susceptibility and differential reactivity was found, findings indicate that those who are susceptible “for better and for worse” may not necessarily be reactive “for better and for worse” as well