In a ‘protected threat’, a baboon induces a dominant member of its group to attack a third one. The baboon appeases the dominant member whom it uses as a tool to threaten the target and manoeuvres to prevent the target from doing the same (Kummer, 1988). This ‘social tool use’ is mastered by baboons at puberty, whereas chimpanzees are adult before they learn to use a stone as a tool for cracking hard nuts (Boesch & Boesch, 1984). Primates appear to manipulate social objects with more ease and sophistication than physical tools.

Observations such as these have suggested that primate intelligence is designed primarily for the social rather than the physical and have led to the Machiavellian intelligence hypothesis (Whiten & Byrne, 1988a) or social intelligence hypothesis (Kummer et al., 1997). The term Machiavellian intelligence emphasises the besting of rivals for personal gain over co-operation, whereas the term social intelligence (which is the more general term) is neutral on the balance between exploitation and co operation.

The social intelligence hypothesis is both stimulating and vague. It is stimulating because it reminds us that whenever psychologists study intelligence and learning in humans or animals, it is almost invariably about inanimate objects: symbols, sticks and bananas. It is vague because the nature of the intelligence it invokes is largely unclear, and as a consequence, the mechanisms of social intelligence have not yet been specified. This combination of exciting and imprecise should be an alarming signal. The social intelligence hypothesis has the seductive power of a political party with no precise programme that allows everyone unhappy with the established system to project his or her own values on it.