Association: one term, five concepts

‘Association’ is certainly one of the most prevalent terms in the study of mind, brain and behavior. It applies to actions, stimuli, neurons, brain areas, ideas, words, etc. However we argue that this term can convey five main meanings, expressing five distinct notions of link, whose coexistence and conflation result in conceptual blurring. This largely underappreciated polysemy problem prevents associative accounts of biological cognitive systems from being properly articulated, understood and criticized. Based on a review traversing psychological, neuronal and behavioral sciences, we delineate and characterize these five categories of usage, to show how such classification improves transparency across fields and casts new light on various debates. The scope is extended to include artificial systems. The review is meant to promote interdisciplinary collaboration and dialogue around the central notion of association.