Today on Nudge, Professor Katie Slocombe shares how chimpanzees handle power, build alliances, and jostle for status in their troop.

It’s the first time on Nudge that we’ve looked at the primate roots of leadership and influence, with plenty of insight into how we humans behave at work (and everywhere else). Don’t miss it. 

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Today’s sources: 

Slocombe, K. E., & Zuberbühler, K. (2007). Chimpanzees modify recruitment screams as a function of audience composition. Proceedings of the National Academy of Sciences of the United States of America, 104(43), 17228–17233.
Slocombe, K. E., Waller, B. M., & Liebal, K. (2011). The language void: The need for multimodality in primate communication research. Animal Behaviour, 81(5), 919–924.

16 years ago a chain of Chinese restaurants wanted to increase sales without changing the price. 

They didn’t change the product. 

The service. 

The chef. 

The food. 

Instead, they changed two words on their menu and increased sales by 18%. 

The restaurants used the advice of today’s guest on Nudge, Robert Cialdini. 

Today, Cialdini explains the social proof principle, sharing how changing just two words could increase your sales.

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Today’s sources: 

Aune, R. K., & Basil, M. D. (1994). A relational-obligations approach to fund-raising: The effects of guilt and credibility appeals on compliance. Communication Research, 21(4), 486–498.

Binning, K. R., Kaufmann, N., McGreevy, E. M., Fotuhi, O., Chen, S., Marshman, E., Kalender, Z. Y., Limeri, L. B., Betancur, L., & Singh, C. (2020). Changing social contexts to foster equity in college science courses: An ecological-belonging intervention. Psychological Science, 31(9), 1059–1070.

Boh, W. F., & Wong, S.-S. (2015). Managers versus co-workers as referents: Comparing social influence effects on within- and outside-subsidiary knowledge sharing. Organizational Behavior and Human Decision Processes, 126, 1–17.

Borman, G. D., Rozek, C. S., Hanselman, P., & Destin, M. (2019). Reappraising academic and social adversity improves middle school students’ academic achievement, behavior, and well-being. Proceedings of the National Academy of Sciences of the United States of America, 116(33), 16286–16291.

Cai, H., Chen, Y., & Fang, H. (2009). Observational learning: Evidence from a randomized natural field experiment. American Economic Review, 99(3), 864–882.

Frank, R. H. (2020). Under the influence: Putting peer pressure to work. Princeton University Press.

Goldstein, N. J., Cialdini, R. B., & Griskevicius, V. (2008). A room with a viewpoint: Using social norms to motivate environmental conservation in hotels. Journal of Consumer Research, 35(3), 472–482.

Hallsworth, M., List, J. A., Metcalfe, R. D., & Vlaev, I. (2017). The behavioralist as tax collector: Using natural field experiments to enhance tax compliance. Journal of Public Economics, 148, 14–31.

Jung, J., Busching, R., & Krahé, B. (2019). Catching aggression from one’s peers: A longitudinal and multilevel analysis. Social and Personality Psychology Compass, 13(4), e12440.

Linder, J. A., Meeker, D., Fox, C. R., Friedberg, M. W., Persell, S. D., Goldstein, N. J., Knight, T. K., Hay, J. W., & Doctor, J. N. (2017). Durability of benefits of behavioral interventions on inappropriate antibiotic prescribing in primary care: Follow-up from a cluster randomized clinical trial. JAMA, 318(14), 1391–1392.

Meeker, D., Linder, J. A., Fox, C. R., Friedberg, M. W., Persell, S. D., Goldstein, N. J., Knight, T. K., Hay, J. W., & Doctor, J. N. (2016). Effect of behavioral interventions on inappropriate antibiotic prescribing among primary care practices: A randomized clinical trial. JAMA, 315(6), 562–570.

Murrar, S., Campbell, M. R., & Brauer, M. (2020). Exposure to peers’ pro-diversity attitudes increases inclusion and reduces the achievement gap. Nature Human Behaviour, 4(9), 889–897.

Nolan, J. M. (2021). Social norm interventions as a tool for pro-climate change. Current Opinion in Psychology, 42, 120–125.

Peterson, R. A., Kim, Y., & Jeong, J. (2020). Out-of-stock, sold out, or unavailable? Framing a product outage in online retailing. Psychology & Marketing, 37(4), 535–547.

I watched Home Alone and suddenly started hearing the theme tune everywhere. 

I thought I was going insane. 

But Tom Bowden-Green and Luan Wise explained that I actually fell for a fairly well-known bias. 

A bias you’ve almost certainly experienced as well. 

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Come to Uplift Live: https://uplift-live.com/

(Use code NUDGE to get £50 off) 

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Today’s sources: 

Costello, J. P., Garvey, A. M., Germann, F., & Wilkie, J. E. B. (2024). The Uptrend Effect: Encouraging healthy behaviors through greater inferred normativity. Journal of Marketing Research, 61(1), 110–127.

Cruz, R. E., Leonhardt, J. M., & Pezzuti, T. (2017). Second person pronouns enhance consumer involvement and brand attitude. Journal of Interactive Marketing, 39(1), 104–116.

Khan, U., & Dhar, R. (2006). Licensing effect in consumer choice. Journal of Marketing Research, 43(2), 259–266.

Lim, S., van Osselaer, S. M., Goodman, J. K., Fuchs, C., & Schreier, M. (2024). The Starbucks effect: When name-based order identification increases customers’ store preference and service satisfaction. Journal of Retailing, 100(2), 316–329.

Sahni, N. S., Wheeler, S. C., & Chintagunta, P. (2018). Personalization in email marketing: The role of noninformative advertising content. Marketing Science, 37(2), 236–258.

Van Boven, L., Dunning, D., & Loewenstein, G. (2000). Egocentric empathy gaps between owners and buyers: Misperceptions of the endowment effect. Journal of Personality and Social Psychology, 79(1), 66–76.

van der Meulen, M. (2022). Are we indeed so illuded? Recency and frequency illusions in Dutch prescriptivism. Languages, 7(1), 42.

Zwicky, A. (2006). Why are we so illuded. Retrieved from https://web.stanford.edu/~zwicky/LSA07illude.abst.pdf

HelloFresh is one of the fastest-growing companies of the past 20 years. 

And it’s down to one, relatively simple behavioural science tactic. 

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Here's Medhi's website: https://tinyurl.com/ymnu6jty

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Today’s sources:

Buechel, E., & Li, R. (2022). Mysterious consumption: Preference for horizontal (vs. vertical) uncertainty and the role of surprise. Journal of Consumer Research, 49(6), 987–1004.

Norton, M. I., Mochon, D., & Ariely, D. (2012). The IKEA effect: When labor leads to love. Journal of Consumer Psychology, 22(3), 453–460.

Skinner, B. F. (1948). “Superstition” in the pigeon. Journal of Experimental Psychology, 38(2), 168–172.

BBC News. (2015, August 12). The man who discovered Harry Potter [Video]. YouTube

Melanie Wass. (2019, September 16). J.K. Rowling – Insights on creating Harry Potter world [Video]. YouTube.

Most of us are completely oblivious to the cognitive biases that dictate how we live our lives. 

Today, with Tom Bowden-Green and Luan Wise, we cover seven cognitive biases that all of us fall for. 

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Today’s sources: 

Chambers, J. R. (2008). Explaining false uniqueness: Why we are both better and worse than others. Social and Personality Psychology Compass, 2(2), 878–894.

Dunning, D. (2011). The Dunning–Kruger effect: On being ignorant of one’s own ignorance. In Advances in experimental social psychology (Vol. 44, pp. 247–296). Academic Press.

Einhorn, H. J., & Hogarth, R. M. (1978). Confidence in judgment: Persistence of the illusion of validity. Psychological Review, 85(5), 395–416.

Helmreich, R., Aronson, E., & LeFan, J. (1970). To err is humanizing sometimes: Effects of self-esteem, competence, and a pratfall on interpersonal attraction. Journal of Personality and Social Psychology, 16(2), 259–264.

Koskie, M. M., & Locander, W. B. (2023). Cool brands and hot attachments: Their effect on consumers’ willingness to pay more. European Journal of Marketing, 57(4), 905–929.

Pronin, E., Lin, D. Y., & Ross, L. (2002). The bias blind spot: Perceptions of bias in self versus others. Personality and Social Psychology Bulletin, 28(3), 369–381.

Van Hoorens, V. (1993). Self-enhancement and superiority biases in social comparison. European Review of Social Psychology, 4, 113–139.

White, G. L., Fishbein, M., & Rutstein, R. C. (1981). Passionate love and the misattribution of arousal. Journal of Personality and Social Psychology, 41(1), 56–62.

“Say you’ve calculated your price and it comes out at £120,121. 

Most would round it down to £120,000. 

That’s completely wrong.” 

That’s what Robert Cialdini told me on the latest episode of Nudge. 

He also explained why the Prime energy drink first succeeded and then flopped. 

How Disney kept us hooked on classic movies. 

And how he applies the authority bias to sell his own products. 

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Read the new and expanded Influence: https://amzn.to/43TY0jI

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Today’s sources: 

Cialdini, R. B. (2021). Influence: The psychology of persuasion (New & expanded ed.). Harper Business.

Dunn, E. W., & Norton, M. I. (2013). Happy money: The science of happier spending. Simon & Schuster.

Nelissen, R. M. A., & Meijers, M. H. C. (2011). Social benefits of luxury brands as costly signals of wealth and status. Evolution and Human Behavior, 32(5), 343–355.

West, S. G. (1975). Increasing the attractiveness of college cafeteria food: A reactance theory perspective. Journal of Applied Psychology, 60(5), 656–658.

Wilson, P. R. (1968). Perceptual distortion of height as a function of ascribed academic status. Journal of Social Psychology, 74(1), 97–102.

Worchel, S., Lee, J., & Adewole, A. (1975). Effects of scarcity on value perception: The cookie-jar study. Journal of Personality and Social Psychology, 31(5), 791–799.

This study analysed 6,700 websites in an unprecedented A/B test. 

The results proved something that Dr Robert Cialdini had been preaching for years. 

Today, on Nudge, Robert Cialdini joins me again, covering another of his seven principles of persuasion. 

And I share a marketing lesson that (I think) every business needs to know.

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Today’s sources: 

Bell, T. [Taylor Bell]. (2025, February 13). Inside Trader Joe’s: The genius strategy behind its cult following (and low prices) [Video]. YouTube.

Bornstein, R. F., Leone, D. R., & Galley, D. J. (1987). The generalizability of subliminal mere exposure effects: Influence of stimuli perceived without awareness on social behavior. Journal of Personality and Social Psychology, 53(6), 1070–1079.

Browne, D., & Swarbrick-Jones, A. (2017). The science of persuasion in e-commerce: An analysis of 6,700 online A/B tests. Conversion Rate Experts.

Danziger, S., Levav, J., & Avnaim-Pesso, L. (2011). Extraneous factors in judicial decisions. Proceedings of the National Academy of Sciences of the United States of America, 108(17), 6889–6892.

Drachman, D., deCarufel, A., & Insko, C. A. (1978). The extra credit effect in interpersonal attraction. Journal of Experimental Social Psychology, 14(5), 458–465.

Fang, X., Singh, S. N., & Ahluwalia, R. (2007). An examination of different explanations for the mere exposure effect. Journal of Consumer Research, 34(1), 97–103.

Gladka, A., & Żemła, M. (2016). Effectiveness of reciprocal rule in tourism: Evidence from a city tourist restaurant. European Journal of Service Management, 17(1), 57–63.

Mita, T. H., Dermer, M., & Knight, J. (1977). Reversed facial images and the mere-exposure hypothesis. Journal of Personality and Social Psychology, 35(8), 597–601.

Nicholson, C. Y., Compeau, L. D., & Sethi, R. (2001). The role of interpersonal liking in building trust in long-term channel relationships. Journal of the Academy of Marketing Science, 29(1), 3–15.

Razran, G. (1940). Conditioned response changes in rating and appraisal. Psychological Bulletin, 37(6), 481–493.

Shotton, R. (2023). The illusion of choice: 16½ psychological biases that influence what we buy. Harriman House.

Strohmetz, D. B., Rind, B., Fisher, R., & Lynn, M. (2002). Sweetening the till: The use of candy to increase restaurant tipping. Journal of Applied Social Psychology, 32(2), 300–309.

Zajonc, R. B., & Rajecki, D. W. (1969). Exposure and affect: A field experiment. Psychonomic Science, 17(4), 216–217.

KFC keeps its recipe secret. 

It’s stored in a vault in an unknown location. 

Only two KFC executives know the ingredients. 

Neither are allowed to fly on the same plane. 

But this secrecy is illogical. The recipe isn’t important. 

Today on Nudge, Richard Shotton explains how the secrecy makes customers more loyal. 

He shares his favourite ad of all time, and we run one of his experiments on you. 

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Today’s sources: 

Heimbach, J. T., & Jacoby, J. (1972). The Zeigarnik effect in advertising. Advances in Consumer Research: Proceedings of the 3rd Annual Conference of the Association for Consumer Research, 746–757.

Loewenstein, G. (1994). The psychology of curiosity: A review and reinterpretation. Psychological Bulletin, 116(1), 75–98.
Zeigarnik, B. (1927). Über das Behalten von erledigten und unerledigten Handlungen. Psychologische Forschung, 9(1), 1–85.

In 1963, the Milgram experiments revealed something unsettling. 

Most people kept administering what they believed were painful electric shocks, not because they wanted to, but because they couldn’t bring themselves to say no. 

In this episode, my guest shares why we agree to extra projects, unpaid favours and unreasonable requests even when we know we shouldn’t. 

I’m joined by behavioural scientist and physician Dr Sunita Sah of Cornell University. She studies how social pressure and conflict-of-interest disclosures can quietly steer us toward yes.

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Today’s sources: 

Milgram, S. (1963). Behavioral study of obedience. Journal of Abnormal and Social Psychology, 67(4), 371–378.

Sah, S. (2025). Defy: The power of no in a world that demands yes. One World.

Sah, S., Loewenstein, G. F., & Cain, D. M. (2013). The burden of disclosure: Increased compliance with distrusted advice. Journal of Personality and Social Psychology, 104(2), 289–304.

Sah, S., Loewenstein, G. F., & Cain, D. M. (2019). Insinuation anxiety: Concern that advice rejection will signal distrust after conflict of interest disclosures. Personality and Social Psychology Bulletin, 45(7), 1099–1112.

Woodzicka, J. A., & LaFrance, M. (2001). Real versus imagined gender harassment. Journal of Social Issues, 57(1), 15–30.

In today’s special end-of-year episode, you’ll hear the best insights from Nudge in 2025.

Hear from Prof. Gerd Gigerenzer, Richard Shotton, Bas Wouters, Philip Graves, Prof. Matt Johnson and a Behavioural Insights Team director. 

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Today’s Sources: 

Beilock, S. L., Bertenthal, B. I., McCoy, A. M., & Carr, T. H. (2004). Haste does not always make waste: Expertise, direction of attention, and speed versus accuracy in performing sensorimotor skills. Psychonomic Bulletin & Review, 11(2), 373–379.

Bellaiche, L., Shahi, R., Turpin, M. H., Ragnhildstveit, A., Sprockett, S., Barr, N., & Seli, P. (2023). Humans versus AI: Whether and why we prefer human-created compared to AI-created artwork. Cognitive Research: Principles and Implications, 8(1), 42.

Groen, J., & Wouters, B. (2020). Online Influence: Boost your results with proven behavioral science. Amazon Digital Services LLC.

Milkman, K. L., Patel, M. S., Gandhi, L., Graci, H. N., Gromet, D. M., Ho, H., Kay, J. S., Lee, T. W., Akinola, M., Beshears, J., Bogard, J. E., Buttenheim, A. M., Chabris, C. F., Chapman, G. B., Duckworth, A. L., Goldstein, N. J., Goren, A., Halpern, S. D., John, L. K., ... & Van den Bulte, C. (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), e2101165118.

Nisbett, R. E., & Wilson, T. D. (1977). Telling more than we can know: Verbal reports on mental processes. Psychological Review, 84(3), 231–259.

van den Broek, E., & den Heijer, T. (2024). The Housefly Effect. Bedford Square Publishers.

Vennard, D., Park, T., & Attwood, S. (2019). Encouraging Sustainable Food Consumption By Using More-Appetizing Language.