The Batman Effect: Do weird surprises make people nicer?

Description

Nobody expects Batman—but when he shows up in a crowded subway car, are people suddenly more likely to help a passenger in need? This week on Normal Curves, we unpack a recent quasi-experimental field study involving a caped superhero costume, a prosthetic pregnancy belly, and some puzzled Italian commuters. Along the way, we demystify three common ways of describing effects for binary outcomes—risk differences, risk ratios, and odds ratios—and explain what they actually mean in plain language. We also do some statistical sleuthing, uncover a major problem hiding in the paper’s numbers, and debate what really counts as an effective Batman outfit.

Statistical topics

• absolute vs relative effects
• binary outcomes
• coding errors
• data errors and quality control
• effect size interpretation
• field experiments
• odds
• odds ratios
• percentage differences
• quasi-experimental studies
• risk differences
• risk ratios
• statistical sleuthing

Methodological morals

• “We love an uncluttered paper, but when it's missing the basics, it's like an empty fridge. Clean, yes, but dinner is not happening.”
• “Before you make a fancy model, make sure the numbers in the table in the text match.”

References

• Pagnini F, Grosso F, Cavalera C, et al. Unexpected events and prosocial behavior: the Batman effect. Npj Ment Health Res. 2025;4(1):57. Published 2025 Nov 3. doi:10.1038/s44184-025-00171-5
• PubPeer. Comments on “Unexpected events and prosocial behavior: the Batman effect.” Accessed December 2025.
• Sainani KL. Understanding odds ratios. PM R. 2011;3(3):263-267. doi:10.1016/j.pmrj.2011.01.009
• Nuzzo RL. Communicating measures of relative risk in plain English. PM R. 2022;14(2):283-287. doi:10.1002/pmrj.12761
• Sainani KL. How statistics can mislead. Am J Public Health. 2012;102:e3-4.

Kristin and Regina’s online courses: 

Demystifying Data: A Modern Approach to Statistical Understanding  

Clinical Trials: Design, Strategy, and Analysis 

Medical Statistics Certificate Program  

Writing in the Sciences 

Epidemiology and Clinical Research Graduate Certificate Program 

Programs that we teach in:

Epidemiology and Clinical Research Graduate Certificate Program 

Find us on:

Kristin -  LinkedIn & Twitter/X

Regina - LinkedIn & ReginaNuzzo.com

• (00:00) - Intro
• (03:42) - Why would Batman make people nicer?
• (07:33) - How they ran the experiment
• (17:50) - Did Batman save the day? Different ways to answer that
• (23:00) - What are odds and odds ratios?
• (30:00) - Where people get it wrong
• (34:52) - The plot twist: big numerical errors
• (41:20) - Did men or women give up their seat more often?
• (43:49) - Wrap-up and methodological morals