This article argues that ritual behaviour was a critical selective force in the emergence of modern cognition. The argument is based on the following observations: (1) Upper Palaeolithic Cro-Magnons exhibited unprecedented levels of social complexity and there is evidence to suggest that this complexity may have begun even earlier in Africa, possibly connected with the Toba eruption. (2) Creating larger, more complex social arrangements, especially those that cut across traditional within-group boundaries, would have required more elaborate and demanding social rituals. (3) Ritual behaviour requiring focused attention and the inhibition of pre-potent responses places demands on areas of the brain known to be associated with working memory. (4) An enhancement of working-memory capacity was very likely necessary for the emergence of modern cognition. (5) The social rituals of traditional societies, which provide the best window on the social rituals of our ancestors, are highly demanding in terms of maintaining focused attention and inhibiting pre-potent responses. (6) Those of our ancestors best able to successfully engage in ritual behaviour would have accrued fitness advantages from increased access to resources, status enhancements and psychophysical health effects. (7) Larger working-memory capacity was very likely a characteristic of these more ritually-capable hominins.