The other group, however, met the kind of doctor all too many of us have encountered: glued to the computer screen throughout the exam, the provider didn’t bother introducing herself and asked questions only to gather practical information. She also stumbled through some of the procedures in the messy exam room and sounded rather unsure of herself.

In both groups, the provider gave patients a cream that she said was an antihistamine to reduce the allergic reaction and decrease itching. The cream was merely unscented hand lotion: a placebo. (A benefit of doing this research in the lab is that for the purposes of the study, we can temporarily lead patients to believe something that is untrue, something doctors could never do in a real clinic visit.)

Decades of robust literature on placebo effects demonstrate that, even without any active ingredients, this cream should reduce the allergic reaction. But no one had examined how the doctor’s demeanor might influence the effects of a placebo treatment.

Our study revealed that the placebo cream reduced participants’ allergic reactions only when the provider projected warmth and competence. When the provider acted colder and less competent, the placebo cream had no effect. It seems that it’s not just what the doctor says about a treatment that matters. It matters how the doctor who says it engages with patients. Doctors who are warmer and more competent are able to set more powerful expectations about medical treatments. Those positive expectations, in turn, have a measurable impact on health.

So, we saw that when the provider projected both desirable qualities of warmth and competence, her words had an effect. When she projected neither, they did not.

What about a provider who seems competent, but not warm? One other group of patients met a provider who seemed highly competent but remained businesslike and distant throughout the interaction, and they did not respond to the placebo cream as much as when the provider acted warm and competent.

Patients of even the most accomplished and skillful doctors may benefit more when that doctor also connects with them.