Research

(for a complete list of publications, please see my CV)

Do people know when to take over tasks?

Levari, D.E., Mastroianni, A.M., Verrey, J.J., Gim, I., Devine, S., & Gilbert, D.T. (Working paper). Do people know when to take over tasks? [email me for more info]

When an individual is performing a task, those who work with them may face a dilemma: would a task takeover – the uninvited act of stepping in to finish a task – improve its outcome? Task takeovers censor information about the performances they interrupt, obscuring their impact. We introduce a method to measure the counterfactual performance of dyads in cooperative tasks, as if those takeovers never happened. A majority of participants took over tasks, made performance worse, and incorrectly believed they made it better. We explore several reasons why takeovers seemed (but were not) helpful, including unanticipated performance trajectories and observational learning. Takeovers are common in cooperative contexts, but people who do so may not realize when they harm the performances they are trying to improve.

Collective streaks motivate prosocial behavior

Levari, D.E. & Norton, M.I. (Working paper). Collective streaks motivate prosocial behavior. [email me for more info]

We introduce a novel method for perpetuating prosocial behavior: highlighting collective streaks of behavior across individuals (e.g., “the last X people in a row have done it”). Across six experiments with over 6,000 participants, asking people to join an ongoing streak of charitable donors or workplace volunteers was more effective than informing them of a high percentage of previous donors (e.g., “X% of people have done it”), because streaks increased feelings of personal impact and signaled that more people would donate in the future. While many streaks in everyday life and organizations involve people who know each other, collective streaks can be effective even when their members are anonymous, and offer a way to encourage prosocial behaviors that are not already popular: stating that 5% of people have donated is far from motivating, stating that 5 people in a row have donated induces further donation.

Advisor performance distorts perceived advice quality and utilization

Levari, D.E. & Feffer, J. (Working paper). Advisor performance distorts perceived advice quality and utilization. [email me for more info]

People often seek advice from friends, teammates, managers, and experts online in order to maximize their performance at various tasks, but what determines how likely they are to follow that advice? While past research has examined the utilization of outcome advice (“what to do”), less is known about how and why people decide to follow performance advice (“how to do”). In four studies, we show that in daily life, the workplace, and lab-based tasks, advisees report following advice from high performers more often, and that they think it is more helpful than other advice. We then introduce a novel paradigm to measure the utilization of performance advice in a complex task, and use it to demonstrate that advisees overestimate how much they follow advice from high performers, as well as how helpful it is. While a person’s performance may be a useful heuristic when seeking out their advice, it may also distort perceptions of how useful that advice is, and even whether or not it was used at all.

Blatantly false news increases belief in news that is merely implausible

Levari, D. E., Martel, C., Orchinik, R., Bhui, R., Seli, P., Pennycook, G., & Rand, D. G. (Working paper). Blatantly false news increases belief in news that is merely implausible. [preprint] [summary on twitter]

What are the consequences of encountering blatant falsehoods and “fake news”? Here we show that exposure to a high prevalence of very implausible claims can increase belief in other, more ambiguous false claims, as they seem more believable in comparison. Participants in five preregistered experiments (N=5,476) were exposed to lower or higher rates of news headlines that seemed blatantly false, as well as some more plausible true and false headlines. Being exposed to a higher prevalence of extremely implausible headlines increased belief in unrelated headlines which were more ambiguous (or even plausible), regardless of whether they were true or false. The effect persisted for headlines describing hypothetical events, as well as actual true and false news headlines. It occurred whether people actively evaluated the headlines or read them passively, among liberals and conservatives, and among those high or low in cognitive reflection. We observed this effect in environments where the plausibility of a claim was a reliable and useful cue to whether it was true or false, and in environments where plausibility and truth were unrelated. We argue that a high prevalence of blatantly implausible claims lowers the threshold of plausibility for other claims to seem believable. Such relative comparisons are a hallmark of the brain’s tendency towards efficient computations in perception and judgment. Even when consumers can reliably identify and disregard blatantly false news content, encountering such content may make subtler falsehoods more likely to be believed.

Tips from the top: Do the best performers really give the best advice?

Levari, D.E., Gilbert, D.T., & Wilson, T.D. (2022). Tips From the Top: Do the Best Performers Really Give the Best Advice?. Psychological Science, 33(5), 685-698. [read] [data/materials/code]

Everyone knows that if you want to learn how to do something, you should get advice from people who do it well. But is everyone right? In a series of studies (N = 8,693), adult participants played a game after receiving performance advice from previous participants. Although advice from the best-performing advisors was no more beneficial than advice from other advisors, participants believed that it had been—and they believed this despite the fact that they were told nothing about their advisors’ performance. Why? The best performers did not give better advice, but they did give more of it, and participants apparently mistook quantity for quality. These studies suggest that performing and advising may often be unrelated skills and that in at least some domains, people may overvalue advice from top performers.

Range-frequency effects can explain and eliminate prevalence-induced concept change

Levari, D.E. (2022). Range-frequency effects can explain and eliminate prevalence-induced concept change. Cognition, Volume 226. [read] [data/materials/code]

Why would concepts seem to grow when their instances become rare? Human observers can respond to decreases in stimulus prevalence by expanding their conceptual boundaries of those stimuli. This prevalence-induced concept change may have serious social consequences, since many real-world detection tasks demand consistent judgments over time. The current work aims to identify the computational process that produces prevalence-induced concept change. I review some plausible models from the cognitive and social sciences that could account for this phenomenon, and then use trial-level computational modeling to see how well each model predicts actual human data, finding that they are best explained as a range-frequency compromise in judgment. Finally, I test an intervention that successfully eliminates prevalence-induced concept change by making stimuli more intense as they become rare.

Prevalence-induced concept change in human judgment

Levari, D.E., Gilbert, D.T., Wilson, T.D., Sievers, B., Amodio, D.M., & Wheatley, T. (2018). Prevalence-induced concept change in human judgment. Science, 360(6396), 1465–1467. [read] [data/materials/code] [text and ratings of the ethical vignettes]

Why do some social problems seem so intractable? In a series of experiments, we show that people often respond to decreases in the prevalence of a stimulus by expanding their concept of it. When blue dots became rare, participants began to see purple dots as blue; when threatening faces became rare, participants began to see neutral faces as threatening; and when unethical requests became rare, participants began to see innocuous requests as unethical. This “prevalence-induced concept change” occurred even when participants were forewarned about it and even when they were instructed and paid to resist it. Social problems may seem intractable in part because reductions in their prevalence lead people to see more of them.