Linnea Gandhi

• Linnea Gandhi, Anoushka Kiyawat, Colin Camerer, Duncan Watts (2025), Hypothetical nudges provide directional but noisy estimates of real behavior change, . Abstract

  Hypothetical scenarios provide an extremely useful alternative to field experiments for scholars interested in nudging behavior change, comprising a substantial proportion of the literature. Yet the extent to which hypotheticals accurately estimate real-world treatment effects is not well understood. To investigate, we identified five recent field studies of real-world nudges in distinct domains and designed four styles of hypothetical scenarios to approximate each one. This setup allows for clear comparison of old field data with new hypothetical data. Across our 20 experiments (N = 16,114), hypothetical scenarios nearly always estimated the correct direction of treatment effects. However, they varied widely in estimating magnitudes, making them unreliable inputs to real-world policy applications such as cost-benefit analyses. Our findings underscore the promising value of hypotheticals, but also the need for greater investigation into strategies to calibrate their estimates.

• Linnea Gandhi, Benjamin Manning, Angela Duckworth (2024), Effect Size Magnification: No Variable is as Important as the One You’re Thinking About—While You’re Thinking About It, . Abstract

  The goal of psychological science is to discover truths about human nature, and the typical form of empirical insights is a simple statement of the form x relates to y. We suggest that such “one-liners” imply much larger x–y relationships than those we typically study. Given the multitude of factors that compete and interact to influence any human outcome, small effect sizes should not surprise us. And yet they do—as evidenced by the persistent and systematic underpowering of research studies in psychological science. We suggest an explanation. Effect size magnification is the tendency to exaggerate the importance of the variable under investigation because of the momentary neglect of others. Although problematic, this attentional focus serves a purpose akin to that of the eye’s fovea. We see a particular x-y relationship with greater acuity when it is the center of our attention. Debiasing remedies are not straightforward, but we recommend (a) recalibrating expectations about the effect sizes we study, (b) proactively exploring moderators and boundary conditions, and (c) periodically toggling our focus from the x variable we happen to study to the non-x variables we do not.

• Linnea Gandhi and Duncan Watts (Work In Progress), Predicting the generalizability of choice architecture interventions.
• Katherine L. Milkman, Linnea Gandhi, Sean F. Ellis, Heather N. Graci, Dena Gromet, Rayyan S. Mobarak, Alison Buttenheim, Angela Duckworth, Devin Pope, Ala Stanford, Richard H Thaler, Kevin Volpp (2022), A Citywide Experiment Testing the Impact of Geographically Targeted, High-Pay-Off Vaccine Lotteries, Nature Human Behaviour. https://doi.org/10.1038/s41562-022-01437-0 Abstract

  Lotteries have been shown to motivate behaviour change in many settings, but their value as a policy tool is relatively untested. We implemented a pre-registered, citywide experiment to test the effects of three high-pay-off, geographically targeted lotteries designed to motivate adult Philadelphians to get their COVID-19 vaccine. In each drawing, the residents of a randomly selected ‘treatment’ zip code received half the lottery prizes, boosting their chances of winning to 50×–100× those of other Philadelphians. The first treated zip code, which drew considerable media attention, may have experienced a small bump in vaccinations compared with the control zip codes: average weekly vaccinations rose by an estimated 61 per 100,000 people per week (+11%). After pooling the results from all three zip codes treated during our six-week experiment, however, we do not detect evidence of any overall benefits. Furthermore, our 95% confidence interval provides a 9% upper bound on the net benefits of treatment in our study.

• Mitesh Patel, Katherine L. Milkman, Linnea Gandhi, Heather N. Graci, Dena Gromet, Hung Ho, Joseph S. Kay, Timothy W. Lee, Jake Rothschild, Modupe Akinola, John Beshears, Jonathan E. Bogard, Alison Buttenheim, Christopher F. Chabris, Gretchen B. Chapman, James J. Choi, Hengchen Dai, Craig R. Fox, Amir Goren, Matthew D. Hilchey, Jillian Hmurovic, Leslie K. John, Dean Karlan, Melanie Kim, David Laibson, Cait Lamberton, Brigitte C. Madrian, M. Meyer, Maria Modanu, Jimin Nam, Todd Rogers, Renante Rondina, Silvia Saccardo, Maheen Shermohammed, Dilip Soman, Jehan Sparks, Caleb Warren, Megan Weber, Ron Berman, Chalanda N. Evans, Seung Hyeong Lee, Christopher K. Snider, Eli Tsukayama, Christophe Van den Bulte, Kevin Volpp, Angela Duckworth (2022), A Randomized Trial of Behavioral Nudges Delivered through Text Messages to Increase Influenza Vaccination Among Patients with an Upcoming Primary Care Visit, American Journal of Health Promotion, 37 (3), pp. 324-332. Abstract

  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.

  Related
  Links
• Katherine L. Milkman, Linnea Gandhi, Mitesh Patel, Heather N. Graci, Dena Gromet, Hung Ho, Joseph S. Kay, Timothy W. Lee, Jake Rothschild, Jonathan E. Bogard, Ilana Brody, Christopher F. Chabris, Edward Chang, Gretchen B. Chapman, Jennifer E. Dannals, Noah J. Goldstein, Amir Goren, Hal E. Hershfield, Alexander Hirsch, Jillian Hmurovic, Samantha Horn, Dean Karlan, Ariella Kristal, Cait Lamberton, M. Meyer, Allison H. Oakes, Maurice Schweitzer, Maheen Shermohammed, Joachim H. Talloen, Caleb Warren, Ashley Whillans, Kuldeep N. Yadav, Julian J. Zlatev, Ron Berman, Chalanda N. Evans, Rahul Ladhania, Jens Ludwig, Nina Mazar, Sendhil Mullainathan, Christopher K. Snider, Jann Spiess, Eli Tsukayama, Lyle Ungar, Christophe Van den Bulte, Kevin Volpp, Angela Duckworth (2022), A 680,000-Person Megastudy of Nudges to Encourage Vaccination in Pharmacies, Proceedings of the National Academy of Sciences, 119 (6). 10.1073/pnas.211512611 Abstract

  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.

• Katherine L. Milkman, Mitesh Patel, Linnea Gandhi, Heather N. Graci, Dena Gromet, Hung Ho, Joseph S. Kay, Timothy W. Lee, Modupe Akinola, John Beshears, Jonathan E. Bogard, Alison Buttenheim, Christopher F. Chabris, Gretchen B. Chapman, James J. Choi, Hengchen Dai, Craig R. Fox, Amir Goren, Matthew D. Hilchey, Jillian Hmurovic, Leslie K. John, Dean Karlan, Melanie Kim, David Laibson, Cait Lamberton, Brigitte C. Madrian, M. Meyer, Maria Modanu, Jimin Nam, Todd Rogers, Renante Rondina, Silvia Saccardo, Maheen Shermohammed, Dilip Soman, Jehan Sparks, Caleb Warren, Megan Weber, Ron Berman, Chalanda N. Evans, Christopher K. Snider, Eli Tsukayama, Christophe Van den Bulte, Kevin Volpp, Angela Duckworth (2021), A Megastudy of Text-Based Nudges Encouraging Patients to Get Vaccinated at an Upcoming Doctor’s Appointment, Proceedings of the National Academy of Sciences, 118 (20). 10.1073/pnas.2101165118 Abstract

  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.

• Linnea Gandhi, “The Integrated Model”. In Building Behavioral Science in an Organization, edited by Zarak Khan & Laurel Newman, (2021)
• Linnea Gandhi and Erik Johnson, 8 Things to Do Before You Run a Business Experiment in Harvard Business Review Online,.
• Daniel Kahneman, Andrew Rosenfield, Linnea Gandhi, Tom Blaser, Noise: How to Overcome the High, Hidden Cost of Inconsistent Decision Making in Harvard Business Review Magazine,.
• All Research from Linnea Gandhi »

Past Courses

• BDS5991 - Independent Study

  The Independent Study is only open to MBDS students.

• BDS5999 - Behavioral Science Ind Cap

  Behavioral Science Individual Capstone for cohorts before 2022.

• OIDD2900 - Decision Processes

  This course is an intensive introduction to various scientific perspectives on the processes through which people make decisions. Perspectives covered include cognitive psychology of human problem-solving, judgment and choice, theories of rational judgment and decision, and the mathematical theory of games. Much of the material is technically rigorous. Prior or current enrollment in STAT 1010 or the equivalent, although not required, is strongly recommended.

• OIDD6590 - Advanced Topics: Supply Chain

  OIDD 6590 enables students to develop modeling skills and a problem-solving toolkit applicable to the design and planning of supply chains. The course is comprised of case studies written by recent MBA students tackling real supply chain analytics problems. Some of the cases covered describe work at Gillette, Google, HP, a franchise fitness studio, and a steel importer. The course covers capacity problems including machine scheduling, strategic sourcing in the presence of tariffs, and network design. The course covers inventory problems including postponement center sizing, multiechelon inventory optimization, and supply chain configuration.

• AOM MOC Best Paper with Practical Implications Award, 2022
• The University of Chicago Booth School of Business, Executive MBA Outstanding TA Award, 2022
• Society for Judgment and Decision Making, Honorable Mention for Conference Poster, 2022
• Penn Presidential PhD Fellow, 2021
• Wharton Risk Center Russell Ackoff Doctoral Fellowship Award, 2021
• Marjorie Weiler Prize for Excellence in Writing, 1970
• Wharton Risk Center Russell Ackoff Doctoral Fellowship Award, 1970
• Analytics at Wharton Grant for “Building a Nudge Map”, 1970
• Analytics at Wharton Grant for “Building a Nudge Map”, 1970

• Nudge Cartography: Building a map to navigate behavioral research, Penn Today - 08/02/2023
• Interview with Linnea Gandhi, Money on the Mind - 07/16/2023
• Presidential Ph.D. Fellows are making their mark, Penn Today - 07/05/2023
• Why Vaccine Lotteries Didn’t Move the Needle on Inoculations, Bloomberg - 10/15/2021
• What We Learned From the Philly Vax Sweepstakes, The Center for Health Incentives and Behavioral Economics - 09/02/2021
• The results of Philadelphia’s COVID-19 vaccine lottery? ‘Discouraging’, WHYY - 08/25/2021
• Penn sponsors 'Philly Vax Sweepstakes' to incentivize Phila. residents to get vaccinated, The Daily Pennsylvanian - 06/17/2021

Knowledge @ Wharton

• The Fed Chair Transition and the Future of Central Bank Independence, Knowledge @ Wharton - 01/09/2026
• Special Report: The AI Skills Gap, Knowledge @ Wharton - 01/09/2026
• Six AI Trends Shaping Business, Education, and Markets in 2026, Knowledge @ Wharton - 01/07/2026
• Data-Driven NFL Playoffs and College Football’s Shifting Power, Knowledge @ Wharton - 01/07/2026
• The Psychology of New Year’s Resolutions | Katy Milkman, Knowledge @ Wharton - 01/06/2026
• How AI and Bayesian Models Are Reshaping Sports Analytics, Knowledge @ Wharton - 12/31/2025
• What to Expect for Real Estate in 2026, Knowledge @ Wharton - 12/31/2025
• What’s Ahead for the U.S. Economy?, Knowledge @ Wharton - 12/26/2025
• What Advanced Metrics Reveal About the 2025 NFL Season, Knowledge @ Wharton - 12/24/2025
• How the Job Market Is Shaping Up for 2026, Knowledge @ Wharton - 12/24/2025