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Director Crum Publishes Intriguing Study on Placebo Effects

November 30, 2016

A Stanford psychology experiment demonstrates that what a bystander says shapes not only what we think about a product, but also how our bodies respond to it. Healthcare providers and patients may use this finding to enhance the effectiveness of medical treatments, suggest the authors of the study, which was published on Nov. 22 in PLOS ONE.

When study participants believed they were drinking a new caffeinated water product, their blood pressure responded as if they had drunk a stimulant. But when a bystander who had also tested the water confided, “I don’t really feel any change; I’m definitely NOT feeling charged up,” participants’ blood pressure fell. Participants who met the unaffected bystander (actually an actor in league with the experimenters) also reported feeling less alert and performed worse on a cognitive test than did participants who did not meet the bystander.

“Many studies have shown that social influence affects people’s thoughts and feelings about a product,” says Alia Crum, an assistant professor of psychology at Stanford and the study’s first author. “But ours is the first study to show that social influence also affects people’s physiological reactions.”

In truth, all participants were drinking un-caffeinated spring water. And so the effects of the beverage arose from participants’ own beliefs and expectations. In other words, the water acted as a placebo. Healthcare providers have long known that pills, surgeries, and other treatments exert placebo effects above and beyond their active ingredients. Yet doctors rarely harness the power of placebos. Meanwhile, enriched water products, called “aquaceuticals,” may very well be using placebo effects to their advantage.

“This paper suggests that healthcare providers may be able amplify placebos by clearly communicating their expectations for success,” says Ted Kaptchuk, a professor of medicine at Harvard Medical School and a placebo expert who was not involved with Crum’s study.

“Patients who are taking the same treatments may also be able to use this finding by confirming to each other, ‘Yes, this drug works well for me,’” says Crum.

In a third experimental condition, participants met a bystander who said, “Wow! This is really waking me up!” Participants who met this affected bystander experienced no reduction in blood pressure. They also felt more alert and performed better on the cognitive test than did participants who met the unaffected bystander.

“Social influence seems to work both ways,” explains Crum. “It can either amplify or dampen the effects of placebos.”

Crum is both principal investigator of the Stanford Mind & Body Lab and the health director of Stanford SPARQ: Social Psychological Answers to Real-world Questions, which are both located in the Stanford Department of Psychology.

The study’s other authors are Damon J. Phillips of Columbia Business School, J. Parker Goyer of Stanford University, Modupe Akinola of Columbia Business School, and E. Tory Higgins of Columbia University.

Download Press Release  Download Study PDF


About the Stanford Mind & Body Lab

Led by Professor Alia Crum, the Stanford Mind & Body Lab studies how subjective mindsets (e.g., thoughts, beliefs, and expectations) can alter objective reality through behavioral, psychological, and physiological pathways. We are interested in how mindsets affect important outcomes both within and beyond the realm of medicine, including the domains of exercise, diet, and stress. 

About Stanford SPARQ: Social Psychological Answers to Real-world Questions

Stanford SPARQ is a do-tank that partners with practitioners to solve real-world problems by applying social science. We conduct, translate, and disseminate research in four action areas: health, criminal justice, education, and economic development. 

Study Citation

Crum AJ, Phillips DJ, Goyer JP, Akinola M, Higgins ET (2016). Transforming Water: Social Influence Moderates Psychological, Physiological, and Functional Response to a Placebo Product. PLoS ONE 11(11): e0167121. doi:10.1371/journal.pone.0167121


Alia Crum

Phone: 970.987.9182