Cognition has reached collectives. It is no longer just sociologists and historians who are trying to understand how groups act, decide, believe or remember. Literary critics of all periods have begun in earnest to study forms of collective cognition in narrative texts. ‘Emotional contagion’, the notion that individuals ‘catch’ the emotions of those around them, has become a resonant idea in several disciplines. Evolutionary psychologists have been asking with renewed intensity how humans evolved to cooperate on an altogether different scale from primates and why it is that they are so much more ‘group-minded’.

In the research that inspired the ‘History of Distributed Cognition’ project, it has in particular been philosophers who are interested in the idea of a ‘group mind’. In common-sense terms, it is evident that it is individuals who have minds, not groups. Indeed, social psychologists have long been making a point of critiquing Gustave Le Bon's classic Psychologie des foules, according to which individuals who come together in a crowd behave as though ‘hypnotised’ (‘comme chez l'hypnotisé’) and are possessed ‘of a sort of collective mind’ (‘une sorte d’âme collective’, Le Bon 1960 [1895]: 31–2, 2). A body of experimental research has shown that group membership, even when temporary, does indeed affect people's thinking, sometimes strikingly so, but that individuals remain capable of individual thought and are able to distance themselves from the thinking of other members of the group.

Arguably, however, the plausibility of the idea of the group mind never rested on common-sense empiricism. Certainly in recent philosophy of mind, the term has proved useful in the context of the wider debates about what is gained and lost if the seat of cognition is conceived as broader than the individual, isolated brain. A growing number of philosophers have been discussing whether and how cognition may usefully be conceptualised not just as embodied, or as a system that involves objects such as a note pad or a smartphone on to which some of the thinking is ‘offloaded’, but also as distributed among a set of individuals. Much of the debate turns on the question of how strong a model of the group mind is most plausible. We are all familiar with statements such as ‘Microsoft changed its mind’. Should one interpret such a phrase as an attribution of mental activity to the corporation as a whole, or is it merely a metonymy?