47 The source of these benefits may well lie, at least in part, in behavioural differences between groups. The most extensively studied of these differences is between the sexes. For example, men have been found to exhibit greater levels of risk-taking than women. 48 The reasons for this appear to be partly physiological, given the larger amounts of testosterone generated by the male body. 49 This risk-taking bias, taken together with the strong male bias within the financial services sector, has led some to posit a causal link between the lack of gender diversity and the global financial crisis. 50 There is also evidence of systematic differences in approaches to decision-making between the sexes. Men tend to attach to a single principle, or heuristic, when making decisions and then stick with it. Women, by contrast, show a greater willingness to switch between decisionmaking principles and heuristics, depending on the context. 51 Or, to caricature things a little, women multi-task while men have one-track minds. Recent neurological research has explored whether there is a link between these behavioural traits and the wiring of the brain using imaging techniques. It is early days. But one recent study found gender differences in the wiring between the left and right cerebral hemispheres, with women exhibiting greater connectivity between hemispheres and men showing greater connectivity within each hemisphere. 52 This wiring difference might explain women’s superiority at multi-tasking and men’s greater spatial awareness. Yet it is important to place these behavioural and cognitive differences in context.

From the late 15th Century onwards, however, the term appears to have taken on negative connotations: “being contrary to what is agreeable or right; perversity; evil”. During the 18th Century, its fortunes changed again. At least some modern democracies began to view diversity as a virtue, a safeguard against any one faction exerting too much power. And from the middle of the 20th century, there has been a surge in the use of the word diversity, as laws and social norms have adapted actively to embrace it. Secular trends – demographic, legal, social – appear, then, to have reshaped the meaning of diversity. Overt discrimination has become unacceptable, legally and socially. Yet while reshaping biases, this changing societal landscape seems unlikely to have eliminated it entirely. Indeed, it is possible that societal shifts may have nurtured a different, more elusive, form of behavioural bias. Like its evolutionary forebears, this is to some extent rational, given the social ecology of the time. During the 20th century, psychologists began documenting work on social interaction in communities of people with differing characteristics. In the 1970s, Henri Tajfel and colleagues discovered that this behaviour often exhibited a strong “in-group” bias. People quickly adopted a social, as well as an individual, identity having attached to a group. For that reason, this has since become known as “social identity theory”. 10 Several important behavioural consequences flow from this theory. Groups become an important source of pride and self-esteem for the individuals attached to them.