Tangles in the social sciences

Traditional clustering identifies groups of objects that share certain qualities. Tangles do the converse: they identify groups of qualities that often occur together. They can thereby identify and discover 'types': of behaviour, views, abilities, dispositions. The mathematical theory of tangles has its origins in the connectivity theory of graphs, which it has transformed over the past 30 years. It has recently been axiomatized in a way that makes its two deepest results applicable to a much wider range of contexts. This expository paper indicates some contexts where this difference of approach is particularly striking. But these are merely examples of such contexts: in principle, it can apply to much of the quantitative social sciences. Our aim here is twofold: to indicate just enough of the theory of tangles to show how this can work in the various different contexts, and to give plenty of different examples illustrating this.