My research program focuses on personality development, more specifically the way that personality and the social environment of a person (i.e., family, peers) interact during development, with successful or less successful development as a result. As such, I study, for example, the role of temperament and personality in the development of problem behavior in young children, but also in the development of personality pathology, of sexuality in (early) adolescence, and of job-searching in later adolescence.

For a part, my research concerns issues of stability and change in personality. I am involved with several longitudinal data-sets (LOGIC, G&P, RADAR, TRAILS, sometimes as PI, sometimes as associate). In several of these data-sets, we have found that personality shows fairly much stability, that is, individual rank orders in all kinds of temperament or personality dimensions do not tend to change much, especially after the age of 3 years old. At the same time, personality is nowhere near perfectly stable, meaning that individuals do change, for better or for worse, in their personality. The amount of change, but even more so the precursors or consequences of change are part of my research focus.

For another part, my research addresses the factors that influence stability and change in personality development. A conceptual model has been formulated (Fraley & Roberts, 2005) that stipulates three mechanisms in personality development: a developmental constant, transactional mechanisms, and stochastic influences. Understanding these mechanisms and how they relate to the consolidation of personality that occurs during childhood, adolescence and young adulthood is part of my research focus. In several studies, we have found that transactional processes are related to personality development: temperament or personality is found to influence children’s relations with parents or peers, which in turn influence their personality. But also stochastic influences have been found to play a role: for parents, their personality seems to be influenced a bit by what happens to their children, and for adolescents, we found that the experience of significant life-events influences their personality. 

My research also explicitly addresses the role of the environment, not only in personality development itself, but also in the way that personality ‘translates’ into problematic behaviour. Regarding this, we repeatedly found evidence for what meanwhile is labelled in terms of ‘differential susceptibility’: some children are, presumably because of their more difficult temperament or personality, more vulnerable to the effects of aversive environmental factors, such as inadequate parenting. This way of looking at the role of the environment in the ‘translation’ of personality into problematic behaviour also has consequences for prevention and intervention, since it means that the focus should not so much be on trying to change the personality of a child, but rather teach children themselves and their environment to handle this personality.

More recently, I have moved the focus of my research more into the direction of psychopathological development. I collaborate with two large institutes for mental health in the Netherlands. Recent studies have demonstrated that ‘normal’ personality development and the development of personality disorders can be seen as closely related. For example, the Big Five framework turns out to be quite useful for the diagnostics and description of personality disorders. This would also mean that the two bodies of knowledge could be combined, so that everything we know about personality development (including, for example, the knowledge of person-environment transactions from my own research line) could be used to understand the development of personality disorders. This could lead to new knowledge, not only in terms of the precursors of personality disorders, but also in terms of the developmental course and the role that the (family, peer) environment might play in this.