Research interests
Although I am interested in many issues in psychology, my
work seems to gravitate around a single question:
What are
psychological attributes? When using words like
"depression" or "neuroticism", what do we designate? A
traditional answer is: latent variables. Latent variables are
structures that are not directly observable, but can be
measured indirectly through their manifestations in behavior.
Thus, the latent variable of depression is measured through
items like "do you feel sad?" and "are you tired?". This idea
has been used to formulate statistical models for psychological
measurement. Today, the assumption that such a model is true
underlies much research in psychology. In early work, I
analyzed the assumptions behind this approach. I concluded
that, to use measurement models profitably, one needs to
interpret the indicator variables (e.g., insomnia, fatigue,
concentration loss)as being caused by the psychological
attribute (e.g., depression). This requirement is unreasonably
strong in many areas of psychology, and this realization drives
the second half of my research life (so far). I developed the
hypothesis that attributes like depression are not latent
variables, but instead are systems of components that reinforce
each other (e.g., insomnia -> fatigue -> concentration
loss). That is, they form
networks . With a team of
methodologists, statisticians, and clinical psychologists, I
have recently initiated the Psychosystems Project (see link
below) in which we apply network modeling and complex systems
techniques to psychopathology and personality. Most of my
research efforts are now dedicated to this project, which is
sponsored by an NWO-Vidi grant.