In experimental economics, where subjects participate in different sessions, observations across subjects of a given session might exhibit more correlation than observations across subjects in different sessions. The main goal of this paper is to clarify what are session-effects: what can cause them, what forms they can take, and what are the potential problems. It will be shown that standard solutions are at times inadequate, and that their properties are sometimes misunderstood.

In 1988 Smith, Suchanek, and Williams (henceforth SSW) introduced a very influential model to test the efficiency of experimental asset markets. They and many subsequent studies observe that bubbles are robust to many treatment changes. Instead, bubbles are avoided only when subjects are experienced in the same setting, when the dividend-process is experienced by subjects beforehand, or when the fundamental value-process (FV) is presented in a well understandable context to reduce subjects’ confusion. We extend this line of research and show that even marginal changes in the experimental instructions/procedure can eliminate bubbles in the SSW-model. In particular, we show that mispricing is significantly reduced and overvaluation is eliminated completely (i) when the fundamental value process is displayed in a graph instead of a table or (ii) when subjects are asked about the current fundamental value at the beginning of each period. From a questionnaire conducted at the end of the experiment we infer that these treatment changes help to improve subjects’ understanding of the FV-process. We conclude that all bubble reducing factors have one common feature: they allow subjects to understand the non-intuitive declining FV-process of the SSW-model better and thus reduce subjects’ confusion about the FV-process.

We examine how multitasking affects performance. We also examine whether individuals optimally choose their degree of multitasking or whether they perform better under an externally imposed schedule. Subjects in our experiment perform two different tasks according to one of three treatments: one where they perform the tasks sequentially, one where they are forced to multitask, and one where they can freely organize their work. Subjects who are forced to multitask perform significantly worse than those forced to work sequentially. Surprisingly, subjects who can freely organize their own schedule also perform significantly worse. These results suggest that scheduling is a significant determinant of productivity. Finally, our results do not support the stereotype that women are better at multitasking. Women suffer as much as men when forced to multitask and are actually less inclined to multitask when being free to choose.

We conduct a framed field experiment in rural Ethiopia to test the seminal hypothesis that insurance provision induces farmers to take greater, yet profitable, risks. Farmers participated in a game protocol in which they were asked to make a simple decision: whether or not to purchase fertilizer and if so, how many bags. The return to fertilizer was dependent on a stochastic weather draw made in each round of the game. In later rounds a random selection of farmers made this decision in the presence of a stylized weather-index insurance contract. Insurance was found to have some positive effect on fertilizer purchases. Purchases were also found to depend on the realization of the weather in the previous round. We explore the mechanisms of this relationship and find that it may be the result of both changes in wealth weather brings about, and changes in perceptions of the costs and benefits to fertilizer purchases.

We explore the effects of the provision of an information-processing instrument—payoff tables—on behavior in experimental oligopolies. In one experimental setting, subjects have access to payoff tables whereas in the other setting they have not. It turns out that this minor variation in presentation has non-negligible effects on participants’ behavior, particularly in the initial phase of the experiment. In the presence of payoff tables, subjects tend to be more cooperative. As a consequence, collusive behavior is more likely and quickly to occur.

This study investigates whether market composition affects individual bidding and the aggregate market in first-price sealed-bid common-value auctions. It compares all-inexperienced markets with only inexperienced bidders, all-experienced markets with only experienced bidders, and mixed markets with both types. On average, there is no market-composition effect for both experienced and inexperienced bidders. When controlling for gender, a market-composition effect appears for inexperienced subjects: Men bid more aggressively in mixed than in all-inexperienced markets, and women bid more aggressively in all-inexperienced markets. On the aggregate level, the all-inexperienced market is the most aggressive with highest winning bids; the all-experienced market is the least aggressive. The mixed market is in between: Both experienced and inexperienced win auctions in this market, but experienced bidders win less auctions than they should.

In this paper we compare behaviour in a newspaper experiment with behaviour in the laboratory. Our workhorse is the Yes-No game. Unlike in ultimatum games responders of the Yes-No games do not know the proposal when deciding whether to accept or not. We use two different amounts that can be shared (100€ and 1000€). Unlike in other experiments with the ultimatum game we find a (small) effect of the size of the stakes. In line with findings for the ultimatum game, we find more generosity among women, older participants, and participants who submit their decision via postal mail than via Internet. By comparing our results with other studies (using executives or students), we demonstrate, at least for this type of game, the external validity of lab research.

We present a new experimental evidence of how framing affects decisions in the context of a lottery choice experiment for measuring risk aversion. We investigate framing effects by replicating the Holt and Laury's (Am. Econ. Rev. 92:1644-1655, 2002) procedure for measuring risk aversion under various frames. We first examine treatments where participants are confronted with the 10 decisions to be made either simultaneously or sequentially. The second treatment variable is the order of appearance of the ten lottery pairs. Probabilities of winning are ranked either in increasing, decreasing, or in random order. Lastly, payoffs were increased by a factor of ten in additional treatments. The rate of inconsistencies was significantly higher in sequential than in simultaneous treatment, in increasing and random than in decreasing treatment. Both experience and salient incentives induce a dramatic decrease in inconsistent behaviors. On the other hand, risk aversion was significantly higher in sequential than in simultaneous treatment, in decreasing and random than in increasing treatment, in high than in low payoff condition. These findings suggest that subjects use available information which has no value for normative theories, like throwing a glance at the whole connected set of pairwise choices before making each decision in a connected set of lottery pairs.

Combinatorial auctions have been studied analytically for several years, but only limited experimental results are available for auctions with more than 10 items. We investigate the Hierarchical Package Bidding auction (HPB), the Combinatorial Clock auction (CC), and one pseudo-dual price auction (PDP) experimentally, as all these formats were used or suggested for high-stakes spectrum auctions. We want to understand the impact that different auction formats have on bidder behavior and allocative efficiency. Interestingly, we find that the main source of inefficiency in all formats is the bidders’ preselection of packages, rather than their strategies or auction rules; bidders mostly preselect a small number of packages of interest early in the auction. CC achieves high efficiency and revenue in all experiments, but HPB yields similar results even in value models, where hierarchical pre-packaging is difficult. Due to their influence on the decision of the US Federal Communications Commission, we intentionally repeated a set of experiments conducted by Goeree and Holt (GH) [Games and Economic Behavior 70:146–169, 2010], and find similar aggregate results. In addition, we analyze the CC auction and find that this mechanism has advantages in environments where the auctioneers’ hierarchy does not fit the bidders’ preferences well. In addition to the value models with global synergies in GH, we used value models where bidders have local synergies, which play a significant role in spectrum auctions in the field and lead to different results.

In an experiment using two-bidder first-price sealed bid auctions with symmetric independent private values and 400 subjects, we scan also the right hand of each subject. We study how the ratio of the length of the index and ring fingers (2D:4D) of the right hand, a measure of prenatal hormone exposure, is correlated with bidding behavior and total profits. 2D:4D has been reported to predict competitiveness in sports competition (Manning and Taylor in Evol. Hum. Behav. 22:61–69, 2001, and Hönekopp et al. in Horm. Behav. 49:545–549, 2006), risk aversion in lottery tasks (Dreber and Hoffman in Portfolio selection in utero. Stockholm School of Economics, 2007; Garbarino et al. in J. Risk Uncertain. 42:1–26, 2011), and the average profitability of high-frequency traders in financial markets (Coates et al. in Proc. Natl. Acad. Sci. 106:623–628, 2009). We do not find any significant correlation between 2D:4D on either bidding or profits. However, there might be racial differences in the correlation between 2D:4D and bidding and profits.

Simulating a real world environment is of utmost importance for achieving accurate and meaningful results in experimental economics. Offering monetary incentives is a common method of creating this environment. In general, experimenters provide the rewards at the time of experiment. In this paper, we argue that receiving the reward at the time of the experiment may lead participants to make decisions as if the money they are using were not their own. To solve this problem, we devised a “prepaid mechanism” that encourages participants to use the money as if it were their own.

We present an experiment designed to test the Modigliani-Miller theorem. Applying a general equilibrium approach and not allowing for arbitrage among firms with different capital structures, we find that, in accordance with the theorem, participants well recognize changes in the systematic risk of equity associated with increasing leverage and, accordingly, demand higher rate of return. Yet, this adjustment is not perfect: subjects underestimate the systematic risk of low-leveraged equity whereas they overestimate the systematic risk of high-leveraged equity, resulting in a U-shaped cost of capital. A (control) individual decision-making experiment, eliciting several points on individual demand and supply curves for shares, provides some support for the theorem.

The presence of implicit observation cues, such as picture of eyes, has been shown to increase generosity in dictator games, and cooperative behavior in field settings. I combine these approaches, by testing if a picture of watching eyes affects unconditional giving in a natural environment, where the recipient is a charity organization. Taken together, this study reduces the influence of three potential confounding factors in previous experiments: (i) experimenter demand effects, (ii) that the facial cue reminds subjects of a human counterpart, and (iii) a social multiplier effect. Specifically, the paper reports results from an experiment, conducted in a Swedish supermarket chain, where customers face a naturally occurring decision problem. People who recycle cans and bottles have to choose whether to keep the recycled amount or donate it to a charity organization. By posting a picture of human eyes on recycling machines, I am able to test whether this causes an increase in donations to the charity. Based on a sample covering a 12-day period, 38 stores and 16775 individual choices, I find no general effect. However, when controlling for store and day fixed effects, and using a proxy for store attendance, the picture of eyes increased donated amount by 30 percent during days when relatively few other people visited the store. This result gives further support to the conclusion that subtle social cues can invoke reputation concerns in humans, although the relatively small effect suggests that previous estimates could be biased upward, or at least that the influence of observational cues is context dependent.

We introduce non-enforceable property rights over a bargaining surplus in a dictator game with production, where the agent's effort is differentially rewarded and subsequently determines the size of the surplus. Using experimental data, we elicit individual preferences over the egalitarian, accountability and libertarian principles and provide evidence to support the inability of these justice principles to individually account for the observed behavior. We show that the justice principle that can be used to explain dictators’ choices depends on whether dictators are paid more or less than recipients for their effort. Our findings suggest that dictators do employ justice principles in self-serving ways and choose in each context the justice principle that maximizes their financial payoffs.

In this paper we study the belief formation processes of a group of outside observers making predictions about the actions of a player involved in a repeated game. We document four main results. First, there is substantial heterogeneity in the accuracy of our observers, with average accuracy being quite poor. Second, while there is no difference between the most and the least accurate observer in their initial beliefs, there are striking differences in their belief updating rules. The most accurate observers have a well-formulated model of player behavior, are good at best responding and quickly incorporate new information to their beliefs. The worst observers behave in an opposite manner on all three fronts. Third, when the game does not converge, subjects look beyond historical actions to make predictions and place more emphasis on forgone payoffs. Finally, we document that a “collective wisdom” emerges when our data are pooled across subjects and analyzed. Specifically, the accuracy of the group estimates becomes much higher than that of the average observer.

Members of organizations are often called upon to trust others and to reciprocate trust while at the same time competing for bonuses or promotions. We suggest that competition affects trust not only within dyads including direct competitors, but also between individuals who do not compete against each other. We test this idea in a trust game where trustors and trustees are rewarded based either on their absolute performance or on how well they do relative to players from other dyads. In Experiment 1, we show that competition among trustors significantly increases trust. Competition among trustees decreases trustworthiness, but trustors do not anticipate this effect. In Experiment 2, we additionally show that the increase in trust under competition is caused by a combination of increased risk taking and lower sensitivity to non-financial concerns specific to trust interactions. Our results suggest that tournament incentives might have a “blinding effect” on considerations such as betrayal and inequality aversion.

Several papers have documented that when subjects play with standard laboratory “endowments” they make less self-interested choices than when they use money they have either earned through a laboratory task or brought from outside the lab. In the context of a charitable giving experiment we decompose this into two common artifacts of the laboratory: the intangibility of money (or experimental currency units) promised on a computer screen relative to cash in hand, and the distinct treatment of random “windfall” gains relative to earned money. While both effects are found to be significant in non-parametric tests, the former effect, which has been neglected in previous studies, has a stronger impact on total donations, while the latter effect has a greater impact on the probability of donating. These results have clear implications for experimental design, and also suggest that the availability of more abstract payment methods may increase other-regarding behavior in the field.