Although beliefs about the effect of affirmative action are widespread, behavioral responses to affirmative actions (from beneficiaries and non-beneficiaries) cannot easily be understood without experimental evidence. In this chapter I review the findings from the experimental literature on two key questions: can affirmative action increase representation without harming efficiency? Are affirmative action beneficiaries penalized by others? The findings highlight that beneficiaries respond to affirmative action as it changes their probability of participating in competitions and it changes their effort level. But the efficiency cost of affirmative action to the society, if any, is small, as affirmative action enhances the participation of highly performing individuals, who would have not participated otherwise. Moreover, beneficiaries do not suffer from backlash from non-beneficiaries. The negative societal impact of affirmative action is therefore likely to be limited.