Psychology’s Replication Problem: Challenging Stack’s Study Of Facial Expressions and Emotional Impact

Posted on August 7, 2019


Screengrab credit to Dorothy Snarker

This is what I mentioned earlier during class regarding replication of psychological studies and the questioning of the validity of past work. Classic studies from across the field have come under fire for issues with replication; Stack’s landmark study on how facial muscle manipulation influences emotion is one of them.


In lab experiments, facial feedback seemed to have a real effect. But it wasn’t clear exactly how the feedback system worked. Were people simply guessing what their faces meant, through some conscious or unconscious action of their minds? Or might smiles work directly on the brain to bring about emotions, without the oversight of higher faculties? In 1985, a social psychologist named Robert Zajonc proposed a modern version of an old and out-of-date idea: Maybe movements of the face affected blood flow to the brain, he said. Perhaps contracting certain facial muscles to smile presses nearby veins in such a way that cooler blood is forced adjacent to the cortex, which in turn produces pleasure. Perhaps the act of frowning does the opposite.

Zajonc tried to prove his zany theory in the lab. In one study, he measured the temperature of subjects’ foreheads while they made different vowel sounds, ee and ü, for which their lips had to be in different postures. (The ü sound made their faces hotter, he reported, and put them in a foul mood.) In another, Zajonc put tubes into the noses of 20 undergraduates and pumped in air of different temperatures. (The students said the cool air made them feel the best.)

Around the time that Zajonc was pursuing this idea, Fritz Strack arrived at the University of Illinois and started doing research as a postdoc. He hadn’t planned to look at facial feedback, but he had some time to dabble. One day in a research meeting, in the spring of 1985, he and another postdoc, Leonard Martin, heard a presentation on the topic. Lots of studies found that if you asked someone to smile, she’d say she felt more happy or amused, and her body would react in kind. It appeared to be a small but reliable effect. But Strack realized that all this prior research shared a fundamental problem: The subjects either knew or could have guessed the point of the experiments. When a psychologist tells you to smile, you sort of know how you’re expected to feel.