 A further category of actors would never act as first movers, however. These are the individuals whose motivation is triggered by the observation of others’ cooperating or by the knowledge that cooperators can observe them… A first subset of this group are motivated by the quasi-moral norm of fairness: it is not fair for us to remain on the sidelines while others are taking risks for our common cause. […] A second subset are motivated by social norms. If noncooperators can be identified and subjected to social ostracism, as is usually the case at the workplace, for example, cooperators may shame them into joining.