Katherine L. Milkman

Jose A. Cervantez and Katherine L. Milkman (2024), Can Nudges Be Leveraged to Enhance Diversity in Organizations? A Systematic Review, Current Opinion in Psychology. https://doi.org/10.1016/j.copsyc.2024.101874

Abstract: In this article, we review and summarize key findings from a growing literature exploring how nudges can facilitate efforts to diversify organizations. Nudges are psychologically-informed interventions that change behavior without restricting choice or altering incentives. We focus on two types of nudges to enhance organizational diversity: (1) nudges that target organizational processes directly or the decision makers who oversee them to increase the diversity of those hired and promoted and (2) nudges that target the underrepresented candidates themselves to increase the diversity of those applying for organizational roles. We categorize nudges designed to enhance organizational diversity, both by their target and based on the psychology they leverage to improve outcomes for women and racial minorities.

Linda W. Chang, Erika Kirgios, Sendhil Mullainathan, Katherine L. Milkman (2024), Does Counting Change What Counts? Quantification Fixation Biases Decision Making, Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.2400215121

Abstract: People often rely on numeric metrics to make decisions and form judgments. Numbers can be difficult to process, leading to their underutilization, but they are also uniquely suited to making comparisons. Do people decide differently when some dimensions of a choice are quantified and others are not? We explore this question across 21 preregistered experiments (8 in the main text, N = 9,303; 13 in supplement, N = 13,936) involving managerial, policy, and consumer decisions. Participants face choices that involve tradeoffs (e.g., choosing between employees, one of whom has a higher likelihood of advancement but lower likelihood of retention), and we randomize which dimension of each tradeoff is presented numerically and which is presented qualitatively (using verbal estimates, discrete visualizations, or continuous visualizations). We show that people systematically shift their preferences toward options that dominate on tradeoff dimensions conveyed numerically—a pattern we dub “quantification fixation.” Further, we show that quantification fixation has financial consequences—it emerges in incentive-compatible hiring tasks and in charitable donation decisions. We identify one key mechanism that underlies quantification fixation and moderates its strength: When making comparative judgments, which are essential to tradeoff decisions, numeric information is more fluent than non-numeric information. Our findings suggest that when we count, we change what counts.

Katherine L. Milkman, Sean F. Ellis, Dena Gromet, Alex S. Luscher, Rayyan S. Mobarak, Madeline K. Paxson, Ramon A. Silvera Zumaran, Robert Kuan, Ron Berman, Neil A. Lewis Jr. John A. List, Mitesh S. Patel, Christophe Van den Bulte, Kevin G. Volpp, Maryann V. Beauvais, Jonathan K. Bellows, Cheryl A. Marandola, Angela Duckworth (2024), Megastudy Shows That Reminders Boost Vaccination But Adding Free Rides Does Not, Nature. https://doi.org/10.1038/s41586-024-07591-x

Abstract: 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 vaccines. One approach to encouraging vaccination is to eliminate the friction of transportation hurdles. Previous research has shown that friction can hinder follow-through and that individuals who live farther from COVID-19 vaccination sites are less likely to get vaccinated. 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.

Aneesh Rai, Edward Chang, Erika Kirgios, Katherine L. Milkman (2024), Group Size and Its Impact on Diversity-Related Perceptions and Hiring Decisions in Homogeneous Groups, Organizational Science. https://doi.org/10.1287/orsc.2020.14705

Abstract: Why do some homogeneous groups face backlash for lacking diversity, whereas others escape censure? We show that a homogeneous group’s size changes how it is perceived and whether decision makers pursue greater diversity in its ranks. We theorize that people make different inferences about larger groups than smaller ones—with consequences for diversity management—due to Bayesian reasoning. This can produce sensitivity to a lack of diversity in large groups and limited sensitivity to a lack of diversity in small groups. Because each group member represents the outcome of a hiring decision, larger homogeneous groups signal a diversity problem more strongly than smaller homogeneous groups. Across three preregistered experiments (n = 4,283), we show that decision makers are more likely to diversify larger homogeneous groups than smaller ones and view larger homogeneous groups as (i) more likely to have resulted from an unfair selection process; (ii) less diverse; (iii) more likely to face diversity-related impression management concerns; and (iv) less open to the influence of newly added underrepresented members. Further, (i)–(iii) mediate the relationship between homogeneous group size and decisions to diversify. We extend our findings to S&P 1500 corporate boards, showing that larger homogeneous boards are more likely to add women or racial minorities as directors. Larger homogeneous boards are also rarer than expected, whereas smaller homogeneous boards are surprisingly abundant. This suggests that decision makers neglect homogeneity in smaller groups, while investing extra effort toward diversifying larger homogeneous groups. Our findings highlight how group size shapes diversity-related perceptions and decisions and identify mechanisms that kickstart diversification efforts.

Rachel Gershon, Cynthia Cryder, Katherine L. Milkman (2024), Friends with Health Benefits: A Field Experiment, Management Science. https://doi.org/10.1287/mnsc.2022.01401

Abstract: When pursuing goals, we commonly choose between going it alone versus teaming up together. In a field experiment (n = 774), we tested the benefits of rewarding individual versus tandem goal pursuit. In a standard-reward condition, we experimentally offered gym members an individual cash reward each day they visited the gym for four weeks. Participants in a tandem-reward condition could earn the same reward but only if they surmounted an extra logistical hurdle: they had to visit the gym with a friend. Although this additional requirement made it more difficult for participants in the tandem-reward condition to earn equivalent incentives, participants with this extra hurdle visited the gym about 35% more frequently than those earning a standard reward. A follow-up survey suggests that tandem rewards provide nonmonetary incentives that change behavior, including increased accountability and enjoyment. Our findings illustrate the advantages of making desired behaviors social to promote follow-through.

Kai Ruggeri, Friederike Stock, S. Alexander Haslam, Valerio Capraro, Paulo Boggio, Naomi Ellemers, Aleksandra Cichoka, Karen M. Douglas, David Rand, Sander van der Linden, Mina Cikara, Eli J. Finkel, James N. Druckman, Michael J.A. Wohl, Richard E. Petty, Joshua A. Tucker, Azim Shariff, Michele Gelfand, Dominic Packer, Jolanda Jetten, Paul A.M. Van Lange, Gordon Pennycook, Ellen Peters, Katherine Biacker, Alia Crum, Kim A. Weeden, Lucy Napper, Nassim Tabri, Jamil Zaki, Linda Skitka, Shinobu Kitayama, Dean Mobbs, Cass R. Sunstein, Sarah Ashcroft-Jones, Anna L. Todsen, Ali Hajian, Sanne Verra, Vanessa Buehler, Maja Friedemann, Marlene Hecht, Rayyan S. Mobarak, Ralitsa Karakasheva, Markus R. Tunte, Siu Kit Yeung, R. Shayna Rosenbaum, Zan Lep, Yuki Yamada, Sa-kiera T.J. Hudson, Lucia Macchia, Irina Soboleva, Eugen Dimant, Sandra J. Geiger, Hannes Jarke, Tobias Wingen, Jana B. Berkessel, Silvana Mareva, Lucy McGill, Francesca Papa, Bojana Veckalov, Zeina Afif, Eike K. Buabang, Marna Landman, Felice Tavera, Jack L. Andrews, Asli Burgalioglu, Zorana Zupan, Lisa Wagner, Joaquin Navajas, Marek Vranka, David Kasdan, Patricia Chen, Kathleen R. Hudson, Lindsay M. Novak, Paul Teas, Nikolay R. Rachev, Matteo M. Galizzi, Marija Petrovic, Katherine L. Milkman, Jay J. Van Bavel, Robb Willer (2023), A Synthesis of Evidence for Policy From Behavioural Science During COVID-19, Nature. https://doi.org/10.1038/s41586-023-06840-9

Abstract: Scientific evidence regularly guides policy decisions, with behavioural science increasingly part of this process. In April 2020, an influential paper proposed 19 policy recommendations (‘claims’) detailing how evidence from behavioural science could contribute to efforts to reduce impacts and end the COVID-19 pandemic. Here we assess 747 pandemic-related research articles that empirically investigated those claims. We report the scale of evidence and whether evidence supports them to indicate applicability for policymaking. Two independent teams, involving 72 reviewers, found evidence for 18 of 19 claims, with both teams finding evidence supporting 16 (89%) of those 18 claims. The strongest evidence supported claims that anticipated culture, polarization and misinformation would be associated with policy effectiveness. Claims suggesting trusted leaders and positive social norms increased adherence to behavioural interventions also had strong empirical support, as did appealing to social consensus or bipartisan agreement. Targeted language in messaging yielded mixed effects and there were no effects for highlighting individual benefits or protecting others. No available evidence existed to assess any distinct differences in effects between using the terms ‘physical distancing’ and ‘social distancing’. Analysis of 463 papers containing data showed generally large samples; 418 involved human participants with a mean of 16,848 (median of 1,699). That statistical power underscored improved suitability of behavioural science research for informing policy decisions. Furthermore, by implementing a standardized approach to evidence selection and synthesis, we amplify broader implications for advancing scientific evidence in policy formulation and prioritization.

Anastasia Buyalskaya, Hung Ho, Katherine L. Milkman, Xiaomen Li, Angela Duckworth, Colin Camerer (2023), What Can Machine Learning Teach Us about Habit Formation? Evidence from Exercise and Hygiene, Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.2216115120

Abstract: 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.

Joseph Reiff, Hengchen Dai, John Beshears, Katherine L. Milkman, Shlomo Benartzi (2023), Save More Today or Tomorrow: The Role of Urgency in Precommitment Design, Journal of Marketing Research. https://doi.org/10.1177/00222437231153396

Abstract: To encourage farsighted behaviors, previous research suggests that marketers should invite consumers to precommit to adopting these behaviors “later.” However, the authors propose that people will draw different inferences from different types of precommitment offers, and that these inferences can help explain when precommitment is (and is not) effective at increasing adoption of farsighted behaviors. Specifically, the authors theorize that simultaneously offering consumers the opportunity to adopt a farsighted behavior now or later (i.e., offering “simultaneous precommitment”) may signal that the behavior is not urgently recommended; however, offering consumers the opportunity to adopt that behavior immediately and then, only if they decline, inviting them to adopt it later (i.e., offering “sequential precommitment”) may signal just the opposite. In a multisite field experiment (N = 5,196), the authors find that simultaneously giving consumers the chance to increase their savings now or later reduced retirement savings. Two preregistered lab studies (N = 5,080) show that simultaneous precommitment leads people to infer that taking action is not urgently recommended, and such inferences predict less adoption of recommended behaviors. Importantly, offering sequential precommitment increases inferred urgency, predicting greater adoption. Together, this research advances knowledge about the limits and potential of precommitment.

Angela Duckworth and Katherine L. Milkman (2022), A Guide to Megastudies, Proceedings of the National Academy of Sciences Nexus. https://doi.org/10.1093/pnasnexus/pgac214

Abstract: 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.

Aneesh Rai, Marissa A. Sharif, Edward H. Chang, Katherine L. Milkman, Angela Duckworth (2022), A Field Experiment on Subgoal Framing to Boost Volunteering: The Trade- Off Between Goal Granularity and Flexibility, Journal of Applied Psychology. https://doi.org/10.1037/apl0001040

Abstract: 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.