Using a controlled experiment, we investigate if individuals' risk preferences are affected by (i) the gender composition of the group to which they are randomly assigned, and (ii) the gender mix of the school they attend. Our subjects, from eight publicly funded single-sex and coeducational schools, were asked to choose between a real-stakes lottery and a sure bet. We found that girls in an all-girls group or attending a single-sex school were more likely than their coed counterparts to choose a real-stakes gamble. This suggests that observed gender differences in behaviour under uncertainty found in previous studies might reflect social learning rather than inherent gender traits.It is well known that women are under-represented in high-paying jobs and in highlevel occupations. Recent work in experimental economics has examined to what degree this under-representation may be due to innate differences between men and women. For example, gender differences in risk aversion, feedback preferences or fondness for competition may help to explain some of the observed gender disparities. If the majority of remuneration in high-paying jobs is tied to bonuses based on a company's performance, then, if men are less risk averse than women, women may choose not to take high-paying jobs because of the uncertainty. Differences in risk attitudes may even affect individual choices about seeking performance feedback or entering a competitive environment.Understanding the extent to which risk attitudes are innate or shaped by environment is important for policy. If risk attitudes are innate, under-representation of women in certain areas may be solved only by changing the way in which remuneration is rewarded. However, if risk attitudes are primarily shaped by the environment, changing the educational or training context could help to address under-representation. Thus, the policy prescription for dealing with under-representation of women in high-paying jobs will depend upon whether the reason for the absence is innate to an individual's gender.Why women and men might have different preferences or risk attitudes has been discussed but not tested by economists. Broadly speaking, those differences may be due to either nurture, nature or some combination of the two. For example, boys are pushed to take risks when participating in competitive sports, whereas girls are often encouraged to remain cautious. Thus, the riskier choices made by men could be due to

JEL classification: C91 C92 J16 J33Keywords: Tournament Piece-rate Gender Experiment Competitive behavior a b s t r a c t Using a controlled experiment, we examine the role of nurture in explaining the stylized fact that women shy away from competition. We have two distinct research questions. First, does the gender composition of the group to which a student is randomly assigned affect competitive choices? Second, does the gender mix of the school a student attends affect competitive choices? Our subjects (students just under 15 years of age) attend publicly funded single-sex and coeducational schools. We find robust differences between the competitive choices of girls from single-sex and coed schools. Moreover, girls from single-sex schools behave more like boys even when randomly assigned to mixed-sex experimental groups. This suggests that it is untrue that the average female avoids competitive behavior more than the average male. It also suggests that observed gender differences might reflect social learning rather than inherent gender traits.

Gender Differences in Risk Aversion: Do Single-Sex Environments Affect their Development? * Single-sex classes within coeducational environments are likely to modify students' risktaking attitudes in economically important ways. To test this, we designed a controlled experiment using first year college students who made choices over real-stakes lotteries at two distinct dates. Students were randomly assigned to classes of three types: all female, all male, and coeducational. They were not allowed to change group subsequently. We found that women are less likely to make risky choices than men at both dates. However, after eight weeks in a single-sex environment, women were significantly more likely to choose the lottery than their counterparts in coeducational groups. These results are robust to the inclusion of controls for IQ and for personality type, as well as to a number of sensitivity tests. Our findings suggest that observed gender differences in behaviour under uncertainty found in previous studies might partly reflect social learning rather than inherent gender traits. JEL Classification:C9, C91, C92, J16, D01, D80, J16, J24

We conduct a field experiment in 31 primary schools in England to test the effectiveness of different temporary incentives on increasing choice and consumption of fruit and vegetables at lunchtime. In each treatment, pupils received a sticker for choosing a fruit or vegetable at lunch. They were eligible for an additional reward at the end of the week depending on the number of stickers accumulated, either individually (individual scheme) or in comparison to others (competition). Overall, we find no significant effect of the individual scheme, but positive effects of competition. For children who had margin to increase their consumption, competition increases choice of fruit and vegetables by 33% and consumption by 48%. These positive effects generally carry over to the week immediately following the treatment, but are not sustained effects six months later. We also find large differences in effectiveness across demographic characteristics such as age and gender.