Time for change
Prof. Paul van Geert started working at the University of Groningen in 1976, one year after he had defended his dissertation at the University of Gent. Less than a decade later, in 1985, he was appointed full professor in Developmental Psychology by her Majesty Queen Beatrix (that’s how it happened in those days). On April 30, 2015, after a wonderful career, he bid farewell to the University of Groningen. This blog post gives an image of his farewell speech.
“Time for change”, Heraclitus said, while he stumbled over his too short legs…
“After I graduated, I started my career in psychological research at the University of Gent in 1971. In those days, we were so poor that we could afford only one subject. And, even worse, we had to make this single subject ourselves… So, I followed my son, David, from the age of one and a half until he was about three, to study his language development. I followed him almost all the time, writing each utterance that he said and its context in a little notebook. From studying these documented (about) 2000 utterances, I learned about the stumbling flow of human development and questioned how psychology can explain it.”
Human development as lasagne?
“The most common road thus far to researching human development comprises looking at characteristics and differences on the population level, by means of investigating if variations in characteristic 1 are related to variations in characteristic 2 (or 3, 4, etc.). The variation of school performance in a particular population, for instance, can be explained by a metaphorical lasagne of motivation + intelligence + … As these relations between characteristics are true for a particular population, the argument goes, they must also be true for individual members of this population. That is to say, the relations can also be translated to individual development (for a more elaborate explanation, see Paul’s block talk at the Heymans Symposium 2015 ). However, with the old Greek philosopher Heraclitus in mind, it is a reasoning error to believe that this approach captures individual development. The relations in individual change are dependent on connections in time – a process that can only occur in concrete, individual cases.”
“So how can you move from general knowledge to individual cases? Well – and here I go again – by means of the theory of complex, dynamic systems. At the core of this theory lie systems that consist of many interacting components, and behave in complex and dynamic ways. Examples of such systems include brains, societies, the weather, insect colonies, and human beings themselves. Over time, the components continuously and inextricably interact, which implies that it is useless to search for what one single component contributes to development (such as intelligence in school performance). For examples of this interaction-dominant perspective on development, see the blog posts on psychological traits  and cognition . Predictions that are derived from this dynamic model of development include principles like self-organization, emergence, specific temporal variance, and the existence of attractor-states (see  or  for (an overview of) papers that describe these principles in more detail).”
“Attractor states can be described as wells to which behavior likes to turn back: they attract. Behavior tends to ‘make a walk’ within that well – sometimes outside, but not that often. An adaptive system is characterized by behavior that is not too rigid or too flexible. Or in other words: wells that are not too deep or too shallow, and not too narrow or too wide. Complex systems that produce such wells are characterized by a particular form of coupling between the components of the system, which can be researched by looking at the variance over time. Here, details, like the described ‘walk’, are just as important as the main lines, as each detail tells you something about details on another level. Even though a system is much more complicated than the one you have selected to describe it, Takens  argues that the behavior of one characteristic gives you information about the whole system’s behavior.“
Variability, broccoli and pink noise
“To capture one characteristic in detail, you collect time-serial data of its behavior, such as, for instance, one year of answers during math-lessons, time between rowing strokes, or sentences within one discussion between a child and a parent. The difference between sequential steps in a time series, or put differently, the variability, varies. Development is discontinuous with changes occurring by leaps and bounds. Such changes in variability have been found to be a hallmark of developmental or clinical jumps, in, for example, language development and depression. Moreover, like broccoli, variability of an adaptive system is self-similar, whereby the structure of big changes (on a large scale) is statistically similar to the structure of small changes (on a smaller scale). This fractal pattern, called ‘pink noise’, is evident in optimal development. For examples and a more extensive explanation, see the blog post on variability . Like timescales, components of a system are also nested. A way to investigate how higher-order constructs emerge from interactions between components is constructing dynamic network models. The blog post about talent development  suggests how such models may contribute to researching development.”
“Lastly, two more things. First of all, the theory of complex dynamic systems has also implications for practice. Interventions, which are intended for changing human behavior, are also complex, adaptive, dynamic systems. Examples of such systems include teacher and coach, or patient, health care worker and family. Second, when I look at my own path as a professor (in terms of graduate students who have been promoted to doctor), it can be characterized as nonlinear, varying and at times even cyclic. In the upcoming years, this complex line with all its branches in the form of the work carried out by my colleagues at the Department of Developmental Psychology, promises to continue bearing fruit.”
“Time for change”… I said.