The Small Lexicon · Complexity Science for Mental Health Care

Simple · Complicated · Complex

A clock is complicated: many parts, but predictable. A human being is complex: the whole cannot be added up from its parts.

What holds for the group by no means always holds for one person. Molenaar showed why averages can mislead here.

The study of the individual case: one person, measured often, over time. This is how the content of a life comes into view.

A measure of the unpredictability of a system. Roughly: high entropy means flexibility, low entropy stuck patterns.

The patterns a system keeps being drawn towards. Some are healthy, others are precisely the problem.

Phase transitions

Sudden leaps, towards better, worse or different. What was stable yesterday may be something new tomorrow.

How an outcome influences the next step. Vicious circles and upward spirals rest on the same mechanism.

Properties that appear at a different level from where you were looking for them, such as consciousness from neurons or a traffic jam from cars.

Self-organisation

Order that arises without a conductor: a system that finds its own patterns, insofar as circumstances allow.

Early warning signals

How a system may signal that it is about to tip. Subtle, but measurable.

Patterns that repeat across different scales: a romanesco, a tree, a river, and perhaps the day, week and year of a patient.

Cycles and rhythms

Recurring patterns in time, such as the sleep-wake rhythm, the weekly rhythm and mood cycles. A person runs on several clocks at once.

Chaos here means sensitivity rather than disorder: a deterministic system that becomes unpredictable through minute differences.

The moment at which a system can go two ways; the underpinning of what we sometimes call a ‘tipping point’.

The science of self-organisation: how many small parts together give rise to a new order.

Order parameter

The quantity that describes the behaviour of the whole and, in turn, orders the parts.

Control parameter

The dial you can turn: not the outcome itself, but a condition that makes it possible.

The imaginary space of all the states a system can assume.

The path a system travels through time, like a route across a map.

Why order costs energy, and why living systems have to be open in order to exist.

When the outcome of one step becomes the input of the next.

Critical instability

The unrest that precedes a transition: a herald rather than a derailment.

Butterfly effect

Why small differences can have large consequences.

Generic principles

The conditions that make self-organisation in processes of change more likely.

Dynamic complexity

A measure of the richness of an unfolding, combining amplitude, frequency and spread.

In the coming months we will expand this lexicon with examples from the consulting room, reading lists for each term and, where possible, short explainer videos. Suggestions are welcome.