Megastudy shows that reminders boost vaccination but adding free rides does not.

Encouraging routine COVID-19 vaccinations is likely to be a crucial policy challenge for decades to come. To avert hundreds of thousands of unnecessary hospitalizations and deaths, adoption will need to be higher than it was in the autumn of 2022 or 2023, when less than one-fifth of Americans received booster vaccines1,2. One approach to encouraging vaccination is to eliminate the friction of transportation hurdles. Previous research has shown that friction can hinder follow-through3 and that individuals who live farther from COVID-19 vaccination sites are less likely to get vaccinated4. However, the value of providing free round-trip transportation to vaccination sites is unknown. Here we show that offering people free round-trip Lyft rides to pharmacies has no benefit over and above sending them behaviourally informed text messages reminding them to get vaccinated. We determined this by running a megastudy with millions of CVS Pharmacy patients in the United States testing the effects of (1) free round-trip Lyft rides to CVS Pharmacies for vaccination appointments and (2) seven different sets of behaviourally informed vaccine reminder messages. Our results suggest that offering previously vaccinated individuals free rides to vaccination sites is not a good investment in the United States, contrary to the high expectations of both expert and lay forecasters. Instead, people in the United States should be sent behaviourally informed COVID-19 vaccination reminders, which increased the 30-day COVID-19 booster uptake by 21% (1.05 percentage points) and spilled over to increase 30-day influenza vaccinations by 8% (0.34 percentage points) in our megastudy. More rigorous testing of interventions to promote vaccination is needed to ensure that evidence-based solutions are deployed widely and that ineffective but intuitively appealing tools are discontinued.

Megastudies improve the impact of applied behavioural science.

Policy-makers are increasingly turning to behavioural science for insights about how to improve citizens' decisions and outcomes1. Typically, different scientists test different intervention ideas in different samples using different outcomes over different time intervals2. The lack of comparability of such individual investigations limits their potential to inform policy. Here, to address this limitation and accelerate the pace of discovery, we introduce the megastudy-a massive field experiment in which the effects of many different interventions are compared in the same population on the same objectively measured outcome for the same duration. In a megastudy targeting physical exercise among 61,293 members of an American fitness chain, 30 scientists from 15 different US universities worked in small independent teams to design a total of 54 different four-week digital programmes (or interventions) encouraging exercise. We show that 45% of these interventions significantly increased weekly gym visits by 9% to 27%; the top-performing intervention offered microrewards for returning to the gym after a missed workout. Only 8% of interventions induced behaviour change that was significant and measurable after the four-week intervention. Conditioning on the 45% of interventions that increased exercise during the intervention, we detected carry-over effects that were proportionally similar to those measured in previous research3-6. Forecasts by impartial judges failed to predict which interventions would be most effective, underscoring the value of testing many ideas at once and, therefore, the potential for megastudies to improve the evidentiary value of behavioural science.

What can machine learning teach us about habit formation? Evidence from exercise and hygiene.

We apply a machine learning technique to characterize habit formation in two large panel data sets with objective measures of 1) gym attendance (over 12 million observations) and 2) hospital handwashing (over 40 million observations). Our Predicting Context Sensitivity (PCS) approach identifies context variables that best predict behavior for each individual. This approach also creates a time series of overall predictability for each individual. These time series predictability values are used to trace a habit formation curve for each individual, operationalizing the time of habit formation as the asymptotic limit of when behavior becomes highly predictable. Contrary to the popular belief in a "magic number" of days to develop a habit, we find that it typically takes months to form the habit of going to the gym but weeks to develop the habit of handwashing in the hospital. Furthermore, we find that gymgoers who are more predictable are less responsive to an intervention designed to promote more gym attendance, consistent with past experiments showing that habit formation generates insensitivity to reward devaluation.

A 680,000-person megastudy of nudges to encourage vaccination in pharmacies.

Encouraging vaccination is a pressing policy problem. To assess whether text-based reminders can encourage pharmacy vaccination and what kinds of messages work best, we conducted a megastudy. We randomly assigned 689,693 Walmart pharmacy patients to receive one of 22 different text reminders using a variety of different behavioral science principles to nudge flu vaccination or to a business-as-usual control condition that received no messages. We found that the reminder texts that we tested increased pharmacy vaccination rates by an average of 2.0 percentage points, or 6.8%, over a 3-mo follow-up period. The most-effective messages reminded patients that a flu shot was waiting for them and delivered reminders on multiple days. The top-performing intervention included two texts delivered 3 d apart and communicated to patients that a vaccine was "waiting for you." Neither experts nor lay people anticipated that this would be the best-performing treatment, underscoring the value of simultaneously testing many different nudges in a highly powered megastudy.

A megastudy of text-based nudges encouraging patients to get vaccinated at an upcoming doctor's appointment.

Many Americans fail to get life-saving vaccines each year, and the availability of a vaccine for COVID-19 makes the challenge of encouraging vaccination more urgent than ever. We present a large field experiment (N = 47,306) testing 19 nudges delivered to patients via text message and designed to boost adoption of the influenza vaccine. Our findings suggest that text messages sent prior to a primary care visit can boost vaccination rates by an average of 5%. Overall, interventions performed better when they were 1) framed as reminders to get flu shots that were already reserved for the patient and 2) congruent with the sort of communications patients expected to receive from their healthcare provider (i.e., not surprising, casual, or interactive). The best-performing intervention in our study reminded patients twice to get their flu shot at their upcoming doctor's appointment and indicated it was reserved for them. This successful script could be used as a template for campaigns to encourage the adoption of life-saving vaccines, including against COVID-19.

Forgoing earned incentives to signal pure motives.

Policy makers, employers, and insurers often provide financial incentives to encourage citizens, employees, and customers to take actions that are good for them or for society (e.g., energy conservation, healthy living, safe driving). Although financial incentives are often effective at inducing good behavior, they've been shown to have self-image costs: Those who receive incentives view their actions less positively due to the perceived incompatibility between financial incentives and intrinsic motives. We test an intervention that allows organizations and individuals to resolve this tension: We use financial rewards to kick-start good behavior and then offer individuals the opportunity to give up some or all of their earned financial rewards in order to boost their self-image. Two preregistered studies-an incentivized online experiment (n = 763) on prosocial behavior and a large field experiment (n = 17,968) on exercise-provide evidence that emphasizing the intrinsic rewards of a past action leads individuals to forgo or donate earned financial rewards. Our intervention allows individuals to retroactively signal that they acted for the right reason, which we call "motivation laundering." We discuss the implications of motivation laundering for the design of incentive systems and behavioral change.

A large-scale field experiment shows giving advice improves academic outcomes for the advisor.

Common sense suggests that people struggling to achieve their goals benefit from receiving motivational advice. What if the reverse is true? In a preregistered field experiment, we tested whether giving motivational advice raises academic achievement for the advisor. We randomly assigned n = 1,982 high school students to a treatment condition, in which they gave motivational advice (e.g., how to stop procrastinating) to younger students, or to a control condition. Advice givers earned higher report card grades in both math and a self-selected target class over an academic quarter. This psychologically wise advice-giving nudge, which has relevance for policy and practice, suggests a valuable approach to improving achievement: one that puts people in a position to give.

The mixed effects of online diversity training.

We present results from a large (n = 3,016) field experiment at a global organization testing whether a brief science-based online diversity training can change attitudes and behaviors toward women in the workplace. Our preregistered field experiment included an active placebo control and measured participants' attitudes and real workplace decisions up to 20 weeks postintervention. Among groups whose average untreated attitudes-whereas still supportive of women-were relatively less supportive of women than other groups, our diversity training successfully produced attitude change but not behavior change. On the other hand, our diversity training successfully generated some behavior change among groups whose average untreated attitudes were already strongly supportive of women before training. This paper extends our knowledge about the pathways to attitude and behavior change in the context of bias reduction. However, the results suggest that the one-off diversity trainings that are commonplace in organizations are unlikely to be stand-alone solutions for promoting equality in the workplace, particularly given their limited efficacy among those groups whose behaviors policymakers are most eager to influence.

Field study of charitable giving reveals that reciprocity decays over time.

We examine how reciprocity changes over time by studying a large quasiexperiment in the field. Specifically, we analyze administrative data from a university hospital system. The data include information about over 18,000 donation requests made by the hospital system via mail to a set of its former patients in the 4 months after their first hospital visit. We exploit quasiexperimental variation in the timing of solicitation mailings relative to patient hospital visits and find that an extra 30-day delay between the provision of medical care and a donation solicitation decreases the likelihood of a donation by 30%. Our findings have important implications for models of economic behavior, which currently fail to incorporate reciprocity's sensitivity to time. The fact that reciprocal behavior decays rapidly as time passes also suggests the importance of capitalizing quickly on opportunities to benefit from a quid pro quo.

Should Governments Invest More in Nudging?

Governments are increasingly adopting behavioral science techniques for changing individual behavior in pursuit of policy objectives. The types of "nudge" interventions that governments are now adopting alter people's decisions without coercion or significant changes to economic incentives. We calculated ratios of impact to cost for nudge interventions and for traditional policy tools, such as tax incentives and other financial inducements, and we found that nudge interventions often compare favorably with traditional interventions. We conclude that nudging is a valuable approach that should be used more often in conjunction with traditional policies, but more calculations are needed to determine the relative effectiveness of nudging.

The effect of interactive reminders on medication adherence: A randomized trial.

Expanding on evidence that interventions to improve health are more effective when informed by behavioral science, we explore whether reminders designed to harness behavioral science principles can improve medication adherence. We conducted a randomized controlled trial with 46,581 U.S. participants with commercial or Medicare Advantage insurance from Humana. Participants were randomly assigned to one of four experimental conditions. Participants in the usual care condition only received standard mailings that the insurer usually sends. In addition to the standard mailings, participants in the other three conditions also received (1) mailings that reminded them to take a target medication (basic reminder condition), (2) reminders that prompted them to predict their medication adherence in the next 30days (prediction condition), or (3) reminders that prompted them to commit to a self-determined level of adherence for the next 30days (commitment condition). We sent these mailings once a month for three months from November, 2014 through January, 2015, and tracked prescription refills. We find that, during the mailing period, reminders increased adherence by 0.95 percentage points (p<0.05), and this effect was driven by the prediction and commitment conditions; during the three-month post-mailing period, reminders increased adherence by 0.98 percentage points (p<0.05), and this effect was driven by the basic reminder and commitment conditions. The reminders increased medication adherence by 0.7 pills per dollar spent over our 181day study period. Trial registry name: Effect of Reminders on Adherence. Registration identification number: NCT02411006 URL for the registry: https://clinicaltrials.gov/ct2/show/NCT02411006.

The science of sharing and the sharing of science.

Why do members of the public share some scientific findings and not others? What can scientists do to increase the chances that their findings will be shared widely among nonscientists? To address these questions, we integrate past research on the psychological drivers of interpersonal communication with a study examining the sharing of hundreds of recent scientific discoveries. Our findings offer insights into (i) how attributes of a discovery and the way it is described impact sharing, (ii) who generates discoveries that are likely to be shared, and (iii) which types of people are most likely to share scientific discoveries. The results described here, combined with a review of recent research on interpersonal communication, suggest how scientists can frame their work to increase its dissemination. They also provide insights about which audiences may be the best targets for the diffusion of scientific content.

Reminders Through Association.

People often fail to follow through on good intentions. While limited self-control is frequently the culprit, another cause is simply forgetting to enact intentions when opportunities arise. We introduce a novel, potent approach to facilitating follow-through: the reminders-through-association approach. This approach involves associating intentions (e.g., to mail a letter on your desk tomorrow) with distinctive cues that will capture attention when you have opportunities to act on those intentions (e.g., Valentine's Day flowers that arrived late yesterday, which are sitting on your desk). We showed that cue-based reminders are more potent when the cues they employ are distinctive relative to (a) other regularly encountered stimuli and (b) other stimuli encountered concurrently. Further, they can be more effective than written or electronic reminder messages, and they are undervalued and underused. The reminders-through-association approach, developed by integrating and expanding on past research on self-control, reminders, and prospective memory, can be a powerful tool for policymakers and individuals.

Put Your Imperfections Behind You: Temporal Landmarks Spur Goal Initiation When They Signal New Beginnings.

People often fail to muster the motivation needed to initiate goal pursuit. Across five laboratory experiments, we explored occasions when people naturally experience enhanced motivation to take actions that facilitate goal pursuit and why certain dates are more likely to spur goal initiation than others. We present causal evidence that emphasizing a temporal landmark denoting the beginning of a new time period increases people's intentions to initiate goal pursuit. In addition, we propose and show that people's strengthened motivation to begin pursuing their aspirations following such temporal landmarks originates in part from the psychological disassociation these landmarks induce from a person's past, imperfect self.

Using implementation intentions prompts to enhance influenza vaccination rates.

We evaluate the results of a field experiment designed to measure the effect of prompts to form implementation intentions on realized behavioral outcomes. The outcome of interest is influenza vaccination receipt at free on-site clinics offered by a large firm to its employees. All employees eligible for study participation received reminder mailings that listed the times and locations of the relevant vaccination clinics. Mailings to employees randomly assigned to the treatment conditions additionally included a prompt to write down either (i) the date the employee planned to be vaccinated or (ii) the date and time the employee planned to be vaccinated. Vaccination rates increased when these implementation intentions prompts were included in the mailing. The vaccination rate among control condition employees was 33.1%. Employees who received the prompt to write down just a date had a vaccination rate 1.5 percentage points higher than the control group, a difference that is not statistically significant. Employees who received the more specific prompt to write down both a date and a time had a 4.2 percentage point higher vaccination rate, a difference that is both statistically significant and of meaningful magnitude.

A field experiment on subgoal framing to boost volunteering: The trade-off between goal granularity and flexibility.

Research suggests that breaking overarching goals into more granular subgoals is beneficial for goal progress. However, making goals more granular often involves reducing the flexibility provided to complete them, and recent work shows that flexibility can also be beneficial for goal pursuit. We examine this trade-off between granularity and flexibility in subgoals in a preregistered, large-scale field experiment (N = 9,108) conducted over several months with volunteers at a national crisis counseling organization. A preregistered vignette pilot study (N = 900) suggests that the subgoal framing tested in the field could benefit goal seekers by bolstering their self-efficacy and goal commitment, and by discouraging procrastination. Our field experiment finds that reframing an overarching goal of 200 hr of volunteering into more granular subgoals (either 4 hr of volunteering every week or 8 hr every 2 weeks) increased hours volunteered by 8% over a 12-week period. Further, increasing subgoal flexibility by breaking an annual 200-hr volunteering goal into a subgoal of volunteering 8 hr every 2 weeks, rather than 4 hr every week, led to more durable benefits. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

A Randomized Trial of Behavioral Nudges Delivered Through Text Messages to Increase Influenza Vaccination Among Patients With an Upcoming Primary Care Visit.

PURPOSE: To evaluate if nudges delivered by text message prior to an upcoming primary care visit can increase influenza vaccination rates. DESIGN: Randomized, controlled trial. SETTING: Two health systems in the Northeastern US between September 2020 and March 2021. SUBJECTS: 74,811 adults. INTERVENTIONS: Patients in the 19 intervention arms received 1-2 text messages in the 3 days preceding their appointment that varied in their format, interactivity, and content. MEASURES: Influenza vaccination. ANALYSIS: Intention-to-treat. RESULTS: Participants had a mean (SD) age of 50.7 (16.2) years; 55.8% (41,771) were female, 70.6% (52,826) were White, and 19.0% (14,222) were Black. Among the interventions, 5 of 19 (26.3%) had a significantly greater vaccination rate than control. On average, the 19 interventions increased vaccination relative to control by 1.8 percentage points or 6.1% (P = .005). The top performing text message described the vaccine to the patient as "reserved for you" and led to a 3.1 percentage point increase (95% CI, 1.3 to 4.9; P < .001) in vaccination relative to control. Three of the top five performing messages described the vaccine as "reserved for you." None of the interventions performed worse than control. CONCLUSIONS: Text messages encouraging vaccination and delivered prior to an upcoming appointment significantly increased influenza vaccination rates and could be a scalable approach to increase vaccination more broadly.

Temporal distance and discrimination: an audit study in academia.

Through a field experiment set in academia (with a sample of 6,548 professors), we found that decisions about distant-future events were more likely to generate discrimination against women and minorities (relative to Caucasian males) than were decisions about near-future events. In our study, faculty members received e-mails from fictional prospective doctoral students seeking to schedule a meeting either that day or in 1 week; students' names signaled their race (Caucasian, African American, Hispanic, Indian, or Chinese) and gender. When the requests were to meet in 1 week, Caucasian males were granted access to faculty members 26% more often than were women and minorities; also, compared with women and minorities, Caucasian males received more and faster responses. However, these patterns were essentially eliminated when prospective students requested a meeting that same day. Our identification of a temporal discrimination effect is consistent with the predictions of construal-level theory and implies that subtle contextual shifts can alter patterns of race- and gender-based discrimination.

A guide to megastudies.

How can behavioral insights best be leveraged to solve pressing policy challenges? Because research studies are typically designed to test the validity of a particular idea, surprisingly little is known about the relative efficacy of different approaches to changing behavior in any given policy context. We discuss megastudies as a research approach that can surmount this and other obstacles to developing optimal behaviorally informed policy interventions. We define a megastudy as "a massive field experiment in which many different treatments are tested synchronously in one large sample using a common, objectively measured outcome." We summarize this apples-to-apples approach to research and lay out recommendations, limitations, and promising future directions for scholars who might want to conduct or evaluate megastudies.

When seeking help, women and racial/ethnic minorities benefit from explicitly stating their identity.

Receiving help can make or break a career, but women and racial/ethnic minorities do not always receive the support they seek. Across two audit experiments-one with politicians and another with students-as well as an online experiment (total n = 5,145), we test whether women and racial/ethnic minorities benefit from explicitly mentioning their demographic identity in requests for help, for example, by including statements like "As a Black woman…" in their communications. We propose that when a help seeker highlights their marginalized identity, it may activate prospective helpers' motivations to avoid prejudiced reactions and increase their willingness to provide support. Here we show that when women and racial/ethnic minorities explicitly mentioned their demographic identity in help-seeking emails, politicians and students responded 24.4% (7.42 percentage points) and 79.6% (2.73 percentage points) more often, respectively. These findings suggest that deliberately mentioning identity in requests for help can improve outcomes for women and racial/ethnic minorities.