**1. Introduction**

Human societies depend on their members acting cooperatively. Social sanctioning is crucial for the maintenance of cooperative behavior when there exist material incentives to deviate from collectively desirable behavior, such as benefiting from a public good without bearing the cost of contributing. Sanctioning behavior can be explained by strong reciprocity, which is defined by a willingness to sacrifice resources to reward cooperative actions and to punish hostile actions even when this is costly and provides neither present nor future material rewards for the reciprocator [1,2]. Thus, individuals acting as norm enforcers enable cooperative behavior because of an understanding and expectation that a deviation will be sanctioned [3]. Social dilemma experiments reveal a great deal of strong reciprocity. For example, in [4], the majority of subjects were willing to engage in *third-party punishment*. That is, they punished a hostile action even though it did not affect their personal earnings.

Is sanctioning a norm violation an *intuitive* response, or does it take *deliberation* to sacrifice resources? To the best of my knowledge this question has not been investigated in the context of *third-party punishment*, where there is no indirect benefit from sanctioning through reputation-building or long-term material incentives from changing the behavior of people one interacts with in the future.

More generally, is cooperative behavior driven by an *intuitive* response or due to *deliberation*? Whether individuals rely on *intuition* or *reflection* in social dilemma experiments has been shown to generate differences in behavior. Applying cognitive reflection tests [5,6], subjects relying on *intuition* in decision-making are found to act more prosocially [7–11].

I contribute to this literature by examining whether behavior is consistent across three games and whether sanctioning the violation of a norm is an *intuitive* action. Applying a *third-party punishment task*, subjects are given the opportunity to, at a personal cost, sanction another subject who kept the entire endowment to herself in the *dictator game.*

Studying subjects' response time has as well been applied to access whether individuals rely on *intuition* in decision-making. Results in these studies are, however, not conclusive about whether a faster response time indicate more prosocial [12] or more egoistic [13] behavior. Identifying whether a choice is *intuitive* or *deliberate* from response time suffers from endogeneity issues as various cognitive processes contribute to response time. When controlling for strength-of-preference, there is no evidence that one type of choice is systematically faster than the other [14].

According to the Social Heuristic Hypothesis, *intuitive* individuals behave more prosocially in the lab because they internalize generally beneficial behavior from daily life that favors cooperative and fair behavior [15]. In light of this, the employed experimental design in this study investigates how strong these internalized fairness preferences are.

The purpose of this study is twofold. By having subjects complete the *dictator game*, the *ultimatum game* (both in the role of *proposer* and *recipient*) and finally the *third-party punishment task* the purpose is first to see if subjects display consistent behavior across games in line with the hypothesis that the "fair" outcome drives *instinctive* choices but that it takes *deliberation* to act selfishly. Secondly, this experiment investigates for the first time if the *instinctive* action is to engage in *third-party punishment* toward a *dictator* who kept the entire endowment to herself in the *dictator game*. The subjects' tendency to rely on *intuition* in decision-making is assessed by Frederick's three-item Cognitive Reflection Test (CRT) [5].

The sample consists of 295 students at Aarhus University, collected during spring 2019.

The results of this study confirmed, first of all, previous findings that *reflective* subjects act more selfishly and in accordance with the economic prediction in the *dictator*- and *ultimatum games*. They transferred less in *dictator game*, they offerred less as the *proposer* in the *ultimatum game*, and they were more likely to accept a low offer as *recipient*. Secondly, the experiment extended previous findings to *third-party punishment* by showing that the *intuitive* action was to sanction a norm-violator. Subjects relying on *intuition* in decision-making were found more likely to sacrifice resources to sanction a *dictator* who kept the entire endowment to herself. Taken together, the results of this experiment provide evidence that the *intuitive* action is to engage in "fair" behavior, or to sanction those not complying with the social norm of fair behavior.

In the following Section 2, I present the experimental design. The hypotheses are presented in Section 3. Section 4 presents the results of the experiment. Section 5 provides a general discussion of the findings. Section 6 discusses the limitations of this study. Section 7 concludes.
