Van der Maas and the leap
How a Dutch psychologist taught us that development is sometimes better described as a leap than as gradual growth.
In Dutch developmental-psychological research, Han van der Maas is, in our view, someone hard to bypass. In the 1990s and 2000s he developed an idea that seems simple at first sight, but from which he distilled an entire research programme: development does not always proceed gradually, sometimes it proceeds in leaps.
It sounds innocent enough. But in a field in which we had until then described cognitive development chiefly as steady growth (first this, then that, then the next), it was a serious intervention. Van der Maas, together with Peter Molenaar, argued that many cognitive transitions — for instance in conservation tasks, in language acquisition, in rule comprehension — can actually be described as catastrophe leaps: the system tips, it does not glide.
What is a catastrophe leap?
The term stems from mathematics — Thom's catastrophe theory, 1960s — and is technical in nature. The core idea, however, can be reasonably understood. Some systems have two possible states in which they can be stable. As an underlying parameter (think: maturation, practice, age) slowly changes, the system first remains in its old state. Until a threshold is reached — and then it tips all at once into the new state.
A fine example that Van der Maas used: children learning to conserve (the insight that the quantity of water remains the same if poured into another glass). Long before they master it, they begin to hesitate — they give inconsistent answers, they doubt, they feel that there is something they do not quite grasp. And then, often within a short period, it tips: suddenly they understand, and they keep understanding.
Why this is important
First: it seems to describe better what we sometimes see in practice. Parents, teachers and developmental clinicians recognise it: a child who is stuck for a long time and then suddenly picks something up. Not because the exercise announced it, but because the system was ripe to tip.
Second: it provides language for what otherwise remains mysterious. The leap is no miracle; rather a property of certain dynamical systems under certain conditions. That makes it in principle studiable.
Third: it has consequences for how we measure. A time series just before a leap has characteristic properties — increasing variance, slower recovery from perturbation, a memory that grows longer. These are "early warning signals" (see also the lexicon entry). One who wishes to see tipping moments must measure differently than one who only compares averages.
The bridge to clinical practice
For mental health care this thinking has implications — cautiously formulated. Sudden gains (the sudden symptom improvements observed in many psychotherapies) resemble such tipping moments in structure. Relapse after a long remission too.
One who has an eye for it often sees preceding signs: an increase in daily variability, a disturbed sleep, an unrest in the attachment relations of a patient. Not always, and not always correctly interpreted — sometimes noise is simply noise. Nevertheless, the thought that a system can prepare itself for a tipping moment offers, to our minds, points of entry for clinical attention.
A modest balance
Van der Maas and his colleagues have over the past decades done much valuable work to empirically ground these ideas. The evidence for catastrophe leaps in cognitive development is, in our view, more robust than that in the clinical context. In the clinical context we still often speak in terms of "could" and "resembles".
As a heuristic for what we sometimes seem to observe in the consulting room, however, the idea seems valuable to us. Not all change follows the clock. Sometimes someone is stuck for a long time and then, suddenly, no longer. That we now have a name and a (cautious) mathematical grounding for this helps, to our minds, to take it seriously — for ourselves and for our patients.