Online labor markets have great potential as platforms for conducting experiments. They provide immediate access to a large and diverse subject pool, and allow researchers to control the experimental context. Online experiments, we show, can be just as valid—both internally and externally—as laboratory and field experiments, while often requiring far less money and time to design and conduct. To demonstrate their value, we use an online labor market to replicate three classic experiments. The first finds quantitative agreement between levels of cooperation in a prisoner's dilemma played online and in the physical laboratory. The second shows— consistent with behavior in the traditional laboratory—that online subjects respond to priming by altering their choices. The third demonstrates that when an identical decision is framed differently, individuals reverse their choice, thus replicating a famed Tversky-Kahneman result. Then we conduct a field experiment showing that workers have upward-sloping labor supply curves. Finally, we analyze the challenges to online experiments, proposing methods to cope with the unique threats to validity in an online setting, and examining the conceptual issues surrounding the external validity of online results. We conclude by presenting our views on the potential role that online experiments can play within the social sciences, and then recommend software development priorities and best practices.

Many previous experiments document that behavior in multi-person settings responds to the name of the game and the labeling of strategies. With a few exceptions, these studies cannot tell whether frames affect preferences or beliefs. In three large experiments, we investigate whether social framing effects are also present in Dictator games. Since only one of the subjects makes a decision, the frame can affect behavior merely through preferences. In all the experiments, we find that behavior is insensitive to social framing. We discuss how to reconcile the absence of social framing effects in Dictator games with the presence of social framing effects in Ultimatum games.

Online experiments allow researchers to collect datasets at times not typical of laboratory studies. We recruit 2336 participants from Amazon Mechanical Turk to examine if participant characteristics and behaviors differ depending on whether the experiment is conducted during the day versus night, and on weekdays versus weekends. Participants make incentivized decisions involving prosociality, punishment, and discounting, and complete a demographic and personality survey. We find no time or day differences in behavior, but do find that participants at nights and on weekends are less experienced with online studies; on weekends are less reflective; and at night are less conscientious and more neurotic. These results are largely robust to finer-grained measures of time and day. We also find that those who participated earlier in the course of the study are more experienced, reflective, and agreeable, but less charitable than later participants.

Political divisions have become a central feature of modern life. Here, we ask whether these divisions affect advice-taking from co- and counter-partisans in a nonpolitical context. In an incentivized task assessing the accuracy of nonpolitical news headlines, we find partisan bias in advice-taking: Democratic participants are less swayed by (accurate) information that comes from Republicans compared to the same information from Democrats (Republican participants display no such bias). We then adjudicate between two possible mechanisms for this biased advice-taking: a preference-based account, where participants are motivated to take less advice from counter-partisans because doing so is unpleasant; versus a belief-based account, where participants sincerely believe co-partisans are more competent at the task (even though this belief is incorrect). To do so, we examine the impact of a substantial increase in the stakes, which should increase accuracy motivations (and thereby reduce the relative impact of partisan motivations). We find that increasing the stakes does not reduce biased advice-taking, hence no evidence to support the bias is driven by preference. Consistent with the belief-based account, we find that Democratic participants (incorrectly) believe their co-partisans are better at the task, and this incorrect belief is much less severe among Republican participants. Further supporting the notion that the stated beliefs are sincere, raising the stakes of the belief elicitation of relative partisan competence does not affect the stated beliefs. Finally, participants—instead of ignoring the feedback—actually substantially update in favor of their counter-partisans given feedback that suggests counter-partisans are competent.

The degree to which individuals prefer smaller sooner versus larger delayed rewards serves as a powerful predictor of their impulsivity towards a number of different kinds of rewards. Here we test the limits of its predictive ability within a variety of cognitive and social domains. Across several large samples of subjects, individuals who prefer smaller more immediate rewards (steeper discounters) are less reflective (or more impulsive) in their choices, preferences, and beliefs. First, steeper discounters used more automatic, less controlled choice strategies, giving more intuitive but incorrect responses on the Cognitive Reflection Test (replicating previous findings); employing a suboptimal probability matching heuristic for a one-shot gamble (rather than maximizing their probability of reward); and relying less on optimal planning in a two-stage reinforcement learning task. Second, steeper discounters preferred to consume information that was less complex and multi-faceted, as suggested by their self-reported Need for Cognitive Closure, their use of short-form social media (i.e., Twitter), and their preferred news sources (in particular, whether or not they preferred National Public Radio over other news sources). Third, steeper discounters had interpersonal and religious beliefs that are associated with reduced epistemic complexity: they were more likely to believe that the behavior of others could be explained by fixed rather than dynamic factors, and they believed more strongly in God and in the afterlife. Together these findings provide evidence for a link between individual differences in temporal discounting for monetary rewards and preferences for the path of least resistance (less reflective and/or more automatic modes of processing) across a variety of domains.

We aggregated data from 28 studies (total N=13,386) to assess the relationship between individual differences in character strengths, as described by the VIA model of character, and economically-relevant behaviors and cognition. Factor analyzing the character strength inventory responses revealed four factors – Caring, Leadership, Inquisitiveness, and Self-control – each of which correlated with a variety of measures. Caring was associated with the willingness to pay costs to benefit others, as well as reliance on intuitive decision-making; Leadership was associated with inefficient, anti-social behaviors, risk taking, and trusting one’s intuitions while also liking to reason; Inquisitiveness was associated with efficient behaviors in both the social and risk domains, and reliance on deliberative decision-making; and Self-control was associated with delaying gratification, risk aversion, and a reliance on reason. These results help shed light on the relationship between character – and personality more generally – and economic behaviors. In doing so, we give some indication of which types of people will be most successful in which decision-making contexts.

Is prosociality parochial or universalist? To shed light on this issue, we examine the relationship between the amount of money given to a stranger (giving in an incentivized Dictator Game) and intergroup attitudes and behavior in the context of randomly assigned teams (a minimal group paradigm) among N = 4,846 Amazon Mechanical Turk workers. Using a set of Dynamic Identity Diffusion Index measures, we find that participants who give more in the Dictator Game show less preferential identification with their team relative to the other team, and more identification with all participants regardless of team. Furthermore, in an incentivized Voter Game, participants who give more in the Dictator Game are more likely to support compromise by voting for the opposing team in order to avoid deadlock. Together, these results suggest that – at least in this subject pool and using these measures – prosociality is better characterized by universalism than parochialism.

Decades of experimental research show that some people forgo personal gains to benefit others in unilateral anonymous interactions. To explain these results, behavioral economists typically assume that people have social preferences for minimizing inequality and/or maximizing efficiency (social welfare). Here we present data that cannot be explained by these standard social preference models. We use a “Trade-Off Game” (TOG), where players unilaterally choose between an equitable option and an efficient option. We show that simply changing the labelling of the options to describe the equitable versus efficient option as morally right completely reverses the correlation between behavior in the TOG and play in a separate Dictator Game (DG) or Prisoner’s Dilemma (PD): people who take the action framed as moral in the TOG, be it equitable or efficient, are much more prosocial in the DG and PD. Rather than preferences for equity and/or efficiency per se, our results suggest that prosociality in games such as the DG and PD are driven by a generalized morality preference that motivates people to do what they think is morally right.

Why is misleading partisan content believed and shared? An influential account posits that political partisanship pervasively biases reasoning, such that engaging in analytic thinking exacerbates motivated reasoning and, in turn, the acceptance of hyperpartisan content. Alternatively, it may be that susceptibility to hyperpartisan content is explained by a lack of reasoning. Across two studies using different participant pools (total N = 1,973 Americans), we had participants assess true, false, and hyperpartisan news headlines taken from social media. We found no evidence that analytic thinking was associated with judging politically consistent hyperpartisan or false headlines to be accurate and unbiased. Instead, analytic thinking was, in most cases, associated with an increased tendency to distinguish true headlines from both false and hyperpartisan headlines (and was never associated with decreased discernment). These results suggest that reasoning typically helps people differentiate between low and high quality political news, rather than facilitate belief in misleading content. Because social media play an important role in the dissemination of misinformation, we also investigated willingness to share headlines on social media. We found a similar pattern whereby analytic thinking was not generally associated with increased willingness to share hyperpartisan or false headlines. Together, these results suggest a positive role for reasoning in resisting misinformation.

Political identification is the basis of enduring conflict, suggesting thatpolitical attitudes are difficult to change. Here we show that in the 2016 U.S.Presidential Election, political identities underwent modification in responseto salient political events. We investigate these dynamics in detail bycollecting data at periodic intervals from mid-June 2016 through the generalelection (N = 3,958). We operationalize identification using prosocial giving inDictator Games played between supporters of competing primary candidatesrecruited from Amazon Mechanical Turk. The observed dynamics differed acrosspolitical parties. In-group bias among Democrats remained high until theDemocratic National Convention, disappeared shortly thereafter, and thenreturned during the final stage of the election. Bias among Republicans wasgenerally high until the final days of the election. The late resurgence of biasamong Democrats was not reflected in voting intentions, but may have presagedthe Democratic election loss.

A substantial body of evidence suggests that favoring reason over intuition (employing an analytic cognitive style) is associated with reduced belief in God. In the current work, we address outstanding issues in this literature with two studies examining the relationship between analytic cognitive style (as measured by performance on the Cognitive Reflection Test) and belief in God. First, prior research focused on Judeo-Christian cultures, and it is uncertain whether the results generalize to other religious systems or beliefs. Study 1 helps to address this question by documenting a negative correlation between CRT performance and belief in God, r = −.18, in a sample of 513 participants from India, a majority Hindu country. Second, among 150 participants from the United Kingdom, Gervais et al. (2018) reported the first and (to date) only evidence for a positive relationship between CRT and belief in God. In Study 2, we assess the robustness of this result by recruiting 547 participants from the United Kingdom. Unlike Gervais et al., using the same items, we find a negative correlation between CRT and belief in God (r = −.19). Our results add further support to the argument that analytic thinking undermines belief in God.

A widely used measure of individual propensity to utilize analytic processing is the Cognitive Reflection Test (CRT), a set of math problems with intuitively compelling but incorrect answers. Here, we ask whether scores on this measure are temporally stable. We aggregate data from 11 studies run on Amazon Mechanical Turk in which the Cognitive Reflection Test (CRT) was administered and identify N = 3,302 unique individuals who completed the CRT two or more times. We find a strong correlation between an individual’s first and last CRT performance, r = .806. This remains true even when constraining to data points separated by over 2 years, r = .755. Furthermore, we find that CRT scores from one timepoint correlated negatively with belief in God and social conservatism from the other timepoint (and to a similar extent as scores gathered at the same timepoint). These results show that CRT scores are stable over time, and – given the stable relationship between CRT and religious belief and ideology – provide some evidence for the stability of analytic cognitive style more generally.

Microcredit – joint-liability loans to the poorest of the poor – has been touted as a powerful approach for combatting global poverty, but sustainability varies dramatically across banks. Efforts to improve the sustainability of microcredit have assumed defaults are caused by free-riding. Here, we point out that the response of other group members to delinquent groupmates also plays an important role in defaults. Even in the absence of any free-rider problem, some people will be unable to make their payments due to bad luck. It is other group members’ unwillingness to pitch in extra – due to, among other things, not wanting to have less than other group members – that leads to default. To support this argument, we utilize the Ultimatum Game (UG), a standard paradigm from behavioral economics for measuring one's aversion to inequitable outcomes. First, we show that country-level variation in microloan default rates is strongly correlated (overall r = 0.81) with country-level UG rejection rates, but not free-riding measures. We then introduce a laboratory model ‘Microloan Game’ and present evidence that defaults arise from inequity-averse individuals refusing to make up the difference when others fail to pay their fair share. This perspective suggests a suite of new approaches for combatting defaults that leverage findings on reducing UG rejections.

Four experiments examine how lack of awareness of inequality affect behaviour towards the rich and poor. In Experiment 1, participants who became aware that wealthy individuals donated a smaller percentage of their income switched from rewarding the wealthy to rewarding the poor. In Experiments 2 and 3, participants who played a public goods game – and were assigned incomes reflective of the US income distribution either at random or on merit – punished the poor (for small absolute contributions) and rewarded the rich (for large absolute contributions) when incomes were unknown; when incomes were revealed, participants punished the rich (for their low percentage of income contributed) and rewarded the poor (for their high percentage of income contributed). In Experiment 4, participants provided with public education contributions for five New York school districts levied additional taxes on mostly poorer school districts when incomes were unknown, but targeted wealthier districts when incomes were revealed. These results shed light on how income transparency shapes preferences for equity and redistribution. We discuss implications for policy-makers.

Whitehouse's model explains when people engage in self-sacrifice, but not who is most likely to do so. We propose incorporating individual differences, such as cognitive style (one's inclination toward intuition versus deliberation), and argue that individuals who rely on intuition may be more likely to (1) develop group identity fusion after an emotional experience and (2) engage in pro-social self-sacrifice.

We argue that the truly unique aspect of human intelligence is not the variety of cognitive skills that are ontogenetically constructed, but rather the capacity to decide when to develop and apply said skills. Even if there is good evidence for g in nonhuman animals, we are left with major questions about how the disposition to think analytically can evolve.

Richerson et al. make a compelling case for cultural evolution. In focusing on cultural group selection, however, they neglect important individual-level accounts of cultural evolution. While scientific discourse typically links cultural evolution to group selection and genetic evolution to individual selection, this association is due to historical accident only. We thus call for more consideration of individual-level cultural evolution.

Many pest and beneficial insects overwinter as larvae in a state of diapause, with development resuming in the spring. In these cases, rates of post-diapause development of parasitoids must be synchronised with the vulnerable life stages of their hosts. Phenological asynchrony between introduced parasitoids and their targeted hosts has limited the success of some biological control efforts. Here, we assess the potential synchrony between Collyria catoptron Wahl (Hymenoptera: Ichneumonidae), a parasitoid of the Chinese wheat stem sawfly, Cephus fumipennis Eversmann (Hymenoptera: Cephidae), which is being considered as a biological control against a novel host species, Cephus cinctus Norton, in North America. We compared development timing and emergence patterns of both native and exotic species of sawflies with that of the parasitoid. We found that the mean number of days between termination of larval diapause and adult eclosion varied by less than one day across species, and patterns of emergence were also similar. The rate of development of this egg-larval parasitoid was within the range necessary to attack C. cinctus eggs. Furthermore, the development of C. cinctus from western Montana, United States of America most closely matched that of the parasitoid, suggesting western Montana as a possible release area.