Standard-Nutzungsbedingungen:Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden.Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen.Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. Abstract In this paper we investigate how the competitiveness of Cournot markets varies with the number of …rms in an industry. We review previous Cournot experiments in the literature. Additionally, we conduct a new series of experiments studying oligopolies with two, three, four, and …ve …rms in a uni…ed frame. With two …rms we …nd some collusion. Three-…rm oligopolies tend to produce outputs at the Nash level. Markets with four or …ve …rms are never collusive and typically settle at or above the Cournot outcome. Some of those markets are actually quite competitive with outputs close to the Walrasian outcome. Terms of use: Documents inJEL-classi…cation numbers: L13, C92, C72.¤ We are indebted to Wieland Müller and Dirk Engelmann for help in conducting the experiments, and to Claudia Keser for suggesting the title of the paper. Doug Davis made very useful comments on an early draft. We are also grateful for …nancial support by the Deutsche Forschungsgemeinschaft, grant OE-198/1/1.

a b s t r a c tWe use a simple, three-item test for cognitive abilities to investigate whether established behavioral biases that play a prominent role in behavioral economics and finance are related to cognitive abilities. We find that higher test scores on the cognitive reflection test of Frederick [Frederick, S., 2005. Cognitive reflection and decision-making. Journal of Economic Perspectives 19, 25-42] indeed are correlated with lower incidences of the conjunction fallacy and conservatism in updating probabilities. Test scores are also significantly related to subjects' time and risk preferences. Test scores have no influence on the amount of anchoring, although there is evidence of anchoring among all subjects. Even if incidences of most biases are lower for people with higher cognitive abilities, they still remain substantial.

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We introduce a generalized theoretical approach to study imitation and subject it to rigorous experimental testing. In our theoretical analysis we find that the different predictions of previous imitation models are due to different informational assumptions, not to different behavioral rules. It is more important whom one imitates rather than how. In a laboratory experiment we test the different theories by systematically varying information conditions. We find significant effects of seemingly innocent changes in information. Moreover, the generalized imitation model predicts the differences between treatments well. The data provide support for imitation on the individual level, both in terms of choice and in terms of perception. But imitation is not unconditional. Rather individuals' propensity to imitate more successful actions is increasing in payoff differences. JEL codes: C72; C91; C92; D43; L13.