Gideon Nave

Evaluating replicability of laboratory experiments in economics

Another social science looks at itself Experimental economists have joined the reproducibility discussion by replicating selected published experiments from two top-tier journals in economics. Camerer et al. found that two-thirds of the 18 studies examined yielded replicable estimates of effect size and direction. This proportion is somewhat lower than unaffiliated experts were willing to bet in an associated prediction market, but roughly in line with expectations from sample sizes and P values. Science, this issue p. 1433 By several metrics, economics experiments do replicate, although not as often as predicted. The replicability of some scientific findings has recently been called into question. To contribute data about replicability in economics, we replicated 18 studies published in the American Economic Review and the Quarterly Journal of Economics between 2011 and 2014. All of these replications followed predefined analysis plans that were made publicly available beforehand, and they all have a statistical power of at least 90% to detect the original effect size at the 5% significance level. We found a significant effect in the same direction as in the original study for 11 replications (61%); on average, the replicated effect size is 66% of the original. The replicability rate varies between 67% and 78% for four additional replicability indicators, including a prediction market measure of peer beliefs.

Does Oxytocin Increase Trust in Humans? A Critical Review of Research

Behavioral neuroscientists have shown that the neuropeptide oxytocin (OT) plays a key role in social attachment and affiliation in nonhuman mammals. Inspired by this initial research, many social scientists proceeded to examine the associations of OT with trust in humans over the past decade. To conduct this work, they have (a) examined the effects of exogenous OT increase caused by intranasal administration on trusting behavior, (b) correlated individual difference measures of OT plasma levels with measures of trust, and (c) searched for genetic polymorphisms of the OT receptor gene that might be associated with trust. We discuss the different methods used by OT behavioral researchers and review evidence that links OT to trust in humans. Unfortunately, the simplest promising finding associating intranasal OT with higher trust has not replicated well. Moreover, the plasma OT evidence is flawed by how OT is measured in peripheral bodily fluids. Finally, in recent large-sample studies, researchers failed to find consistent associations of specific OT-related genetic polymorphisms and trust. We conclude that the cumulative evidence does not provide robust convergent evidence that human trust is reliably associated with OT (or caused by it). We end with constructive ideas for improving the robustness and rigor of OT research.

Is there a Publication Bias in Behavioural Intranasal Oxytocin Research on Humans? Opening the File Drawer of One Laboratory.

The neurohormone oxytocin (OT) has been one the most studied peptides in behavioural sciences over the past two decades. Primarily known for its crucial role in labour and lactation, a rapidly growing literature suggests that intranasal OT (IN‐OT) may also play a role in the emotional and social lives of humans. However, the lack of a convincing theoretical framework explaining the effects of IN‐OT that would also allow the prediction of which moderators exert their effects and when has raised healthy skepticism regarding the robustness of human behavioural IN‐OT research. Poor knowledge of the exact pharmacokinetic properties of OT, as well as crucial statistical and methodological issues and the absence of direct replication efforts, may have lead to a publication bias in the IN‐OT literature, with many unpublished studies with null results remaining buried in laboratory drawers. Is there a file drawer problem in IN‐OT research? If this is the case, it may also be true in our own laboratory. The present study aims to answer this question, document the extent of the problem and discuss its implications for OT research. For eight studies (including 13 dependent variables overall, as assessed through 25 different paradigms) performed in our laboratory between 2009 and 2014 on 453 subjects, the results obtained were too often not those that were expected. Only five publications emerged from our studies and only one of these reported a null finding. After realising that our publication portfolio has become less and less representative of our actual findings and because the nonpublication of our data might contribute to generating a publication bias in IN‐OT research, we decided to retrieve these studies from our drawer and encourage other laboratories to do the same.

Single-Dose Testosterone Administration Impairs Cognitive Reflection in Men:

In nonhumans, the sex steroid testosterone regulates reproductive behaviors such as fighting between males and mating. In humans, correlational studies have linked testosterone with aggression and disorders associated with poor impulse control, but the neuropsychological processes at work are poorly understood. Building on a dual-process framework, we propose a mechanism underlying testosterone’s behavioral effects in humans: reduction in cognitive reflection. In the largest study of behavioral effects of testosterone administration to date, 243 men received either testosterone or placebo and took the Cognitive Reflection Test (CRT), which estimates the capacity to override incorrect intuitive judgments with deliberate correct responses. Testosterone administration reduced CRT scores. The effect remained after we controlled for age, mood, math skills, whether participants believed they had received the placebo or testosterone, and the effects of 14 additional hormones, and it held for each of the CRT questions in isolation. Our findings suggest a mechanism underlying testosterone’s diverse effects on humans’ judgments and decision making and provide novel, clear, and testable predictions.

Psychological targeting as an effective approach to digital mass persuasion

Significance Building on recent advancements in the assessment of psychological traits from digital footprints, this paper demonstrates the effectiveness of psychological mass persuasion—that is, the adaptation of persuasive appeals to the psychological characteristics of large groups of individuals with the goal of influencing their behavior. On the one hand, this form of psychological mass persuasion could be used to help people make better decisions and lead healthier and happier lives. On the other hand, it could be used to covertly exploit weaknesses in their character and persuade them to take action against their own best interest, highlighting the potential need for policy interventions. People are exposed to persuasive communication across many different contexts: Governments, companies, and political parties use persuasive appeals to encourage people to eat healthier, purchase a particular product, or vote for a specific candidate. Laboratory studies show that such persuasive appeals are more effective in influencing behavior when they are tailored to individuals’ unique psychological characteristics. However, the investigation of large-scale psychological persuasion in the real world has been hindered by the questionnaire-based nature of psychological assessment. Recent research, however, shows that people’s psychological characteristics can be accurately predicted from their digital footprints, such as their Facebook Likes or Tweets. Capitalizing on this form of psychological assessment from digital footprints, we test the effects of psychological persuasion on people’s actual behavior in an ecologically valid setting. In three field experiments that reached over 3.5 million individuals with psychologically tailored advertising, we find that matching the content of persuasive appeals to individuals’ psychological characteristics significantly altered their behavior as measured by clicks and purchases. Persuasive appeals that were matched to people’s extraversion or openness-to-experience level resulted in up to 40% more clicks and up to 50% more purchases than their mismatching or unpersonalized counterparts. Our findings suggest that the application of psychological targeting makes it possible to influence the behavior of large groups of people by tailoring persuasive appeals to the psychological needs of the target audiences. We discuss both the potential benefits of this method for helping individuals make better decisions and the potential pitfalls related to manipulation and privacy.

Exogenous cortisol causes a shift from deliberative to intuitive thinking

People often rely on intuitive judgments at the expense of deliberate reasoning, but what determines the dominance of intuition over deliberation is not well understood. Here, we employed a psychopharmacological approach to unravel the role of two major endocrine stress mediators, cortisol and noradrenaline, in cognitive reasoning. Healthy participants received placebo, cortisol (hydrocortisone) and/or yohimbine, a drug that increases noradrenergic stimulation, before performing the cognitive reflection test (CRT). We found that cortisol impaired performance in the CRT by biasing responses toward intuitive, but incorrect answers. Elevated stimulation of the noradrenergic system, however, had no effect. We interpret our results in the context of the dual systems theory of judgment and decision making. We propose that cortisol causes a shift from deliberate, reflective cognition toward automatic, reflexive information processing.

Evaluating the replicability of social science experiments in Nature and Science between 2010 and 2015

Being able to replicate scientific findings is crucial for scientific progress1–15. We replicate 21 systematically selected experimental studies in the social sciences published in Nature and Science between 2010 and 201516–36. The replications follow analysis plans reviewed by the original authors and pre-registered prior to the replications. The replications are high powered, with sample sizes on average about five times higher than in the original studies. We find a significant effect in the same direction as the original study for 13 (62%) studies, and the effect size of the replications is on average about 50% of the original effect size. Replicability varies between 12 (57%) and 14 (67%) studies for complementary replicability indicators. Consistent with these results, the estimated true-positive rate is 67% in a Bayesian analysis. The relative effect size of true positives is estimated to be 71%, suggesting that both false positives and inflated effect sizes of true positives contribute to imperfect reproducibility. Furthermore, we find that peer beliefs of replicability are strongly related to replicability, suggesting that the research community could predict which results would replicate and that failures to replicate were not the result of chance alone.Camerer et al. carried out replications of 21 Science and Nature social science experiments, successfully replicating 13 out of 21 (62%). Effect sizes of replications were about half of the size of the originals.

Vasopressin increases human risky cooperative behavior

Significance Most forms of cooperative behavior take place in a mutually beneficial context where cooperation is risky as its success depends on unknown actions of others. In two pharmacological experiments, we show that intranasal administration of arginine vasopressin (AVP), a hormone that regulates mammalian social behaviors such as monogamy and aggression, increases humans’ tendency to engage in mutually beneficial cooperation. Several control tasks ruled out that AVP’s effects were driven by increased willingness to bare risks in the absence of social context, beliefs about the actions of one’s partner, or altruistic concerns. Our findings provide novel causal evidence for a biological factor underlying cooperation and are in accord with previous findings that cooperation is intrinsically rewarding for humans. The history of humankind is an epic of cooperation, which is ubiquitous across societies and increasing in scale. Much human cooperation occurs where it is risky to cooperate for mutual benefit because successful cooperation depends on a sufficient level of cooperation by others. Here we show that arginine vasopressin (AVP), a neuropeptide that mediates complex mammalian social behaviors such as pair bonding, social recognition and aggression causally increases humans’ willingness to engage in risky, mutually beneficial cooperation. In two double-blind experiments, male participants received either AVP or placebo intranasally and made decisions with financial consequences in the “Stag hunt” cooperation game. AVP increases humans’ willingness to cooperate. That increase is not due to an increase in the general willingness to bear risks or to altruistically help others. Using functional brain imaging, we show that, when subjects make the risky Stag choice, AVP down-regulates the BOLD signal in the left dorsolateral prefrontal cortex (dlPFC), a risk-integration region, and increases the left dlPFC functional connectivity with the ventral pallidum, an AVP receptor-rich region previously associated with AVP-mediated social reward processing in mammals. These findings show a previously unidentified causal role for AVP in social approach behavior in humans, as established by animal research.

Extrapolative Beliefs in Perceptual and Economic Decisions: Evidence of a Common Mechanism

A critical component of both economic and perceptual decision making under uncertainty is the belief-formation process. However, most research has studied belief formation in economic and perceptual decision making in isolation. One reason for this separate treatment may be the assumption that there are distinct psychological mechanisms that underlie belief formation in economic and perceptual decisions. An alternative theory is that there exists a common mechanism that governs belief formation in both domains. Here, we test this alternative theory by combining a novel computational modeling technique with two well-known experimental paradigms. We estimate a drift-diffusion model (DDM) and provide an analytical method to decode prior beliefs from DDM parameters. Subjects in our experiment exhibit strong extrapolative beliefs in both paradigms. In line with the common mechanism hypothesis, we find that a single computational model explains belief formation in both tasks and that individual differences in b...

Combined Effects of Glucocorticoid and Noradrenergic Activity on Loss Aversion

Loss aversion is a well-known behavioral regularity in financial decision making, describing humans’ tendency to overweigh losses compared to gains of the same amount. Recent research indicates that stress and associated hormonal changes affect loss aversion, yet the underlying neuroendocrine mechanisms are still poorly understood. Here, we investigated the causal influence of two major stress neuromodulators, cortisol and noradrenaline, on loss aversion during financial decision making. In a double-blind, placebo-controlled between-subject design, we orally administered either the α2-adrenergic antagonist yohimbine (increasing noradrenergic stimulation), hydrocortisone, both substances, or a placebo to healthy young men. We tested the treatments’ influence on a financial decision-making task measuring loss aversion and risk attitude. We found that both drugs combined, relative to either drug by itself, reduced loss aversion in the absence of an effect on risk attitude or choice consistency. Our data suggest that concurrent glucocorticoid and noradrenergic activity prompts an alignment of reward- with loss-sensitivity, and thus diminishes loss aversion. Our results have implications for the understanding of the susceptibility to biases in decision making.