Don’t Say Can’t: How Word Play Drives Behavioral Change

Word choice does matter, as this study reveals

By Peter M. Vishton, PhDWilliam & Mary
Edited by Kate Findley and proofread by Angela Shoemaker, Wondrium Daily

If you want to change a behavior or quit an unhealthy habit, your word choices make a bigger difference than you might think. Professor Vishton explains.

Man looking in mirror exploring self talk
When you say “can’t,” your brain activates associations involving external controls that affect your behavior, but if you say “don’t,” your brain activates associations with internal controls, within yourself, that affect behavior. Photo By Dean Drobot / Shutterstock

“Don’t” Versus “Can’t” Study

Specifically, using the word “don’t” rather than “can’t” can greatly increase your chances of succeeding. University of Houston Marketing Professor Vanessa Patrick and her colleagues explored this idea with the task of promoting healthy eating, but related studies suggest that the results can apply to many types of behavioral change.

Imagine you are at a dinner with someone. You’ve decided to cut down on desserts. It is, however, time for dessert, and you feel tempted. 

Perhaps someone offers you a delicious slice of cheesecake. How would you respond? 

Many people would say something like, “No thank you. I can’t eat desserts anymore.” However, we also phrase this as, “No thank you. I don’t eat desserts anymore.”

The key words here are “can’t” and “don’t.” Most English speakers know the difference between the definition of those two words, but we use them almost interchangeably in regular conversation about changing our behaviors.

Does External Motivation Work?

Patrick and her colleagues drew from a range of research on the nature of how people respond to different types of motivation. In some cases, our behaviors are influenced by external controls. 

If your boss tells you to be at work at 8:00 a.m. or else, then your early morning behaviors will be influenced by this external control. In other cases, our behaviors are motivated by internal controls. 

Maybe you decide to be more productive during the day, so you start work by 8:00 a.m. The behavior here is the same in both cases—you get to work by 8:00 a.m.—but the causes are different.

When people are motivated by external controls, they tend to be less consistent in their behaviors over the long term—especially if the external controller is absent. If you know your boss is on vacation one week, the external control will be weakened, whereas, the internal control won’t be affected. 

When you say you can’t do something, your brain activates things associated with that word “can’t.” One of those associations involves external controls. If you instead say “don’t,” your brain is more likely to activate associations with internal controls.

Word Choice and Behavior Study

To test whether the differential use of these words affects actual behavior, Patrick recruited a large group of participants who were interested in improving their eating habits. They were asked to rate some instructions about a new method that would be used in a future study to improve other people’s eating behaviors. 

Note that in this study, the participants weren’t being enrolled in the program at all. The experimenters were just asking them to rate how they felt about this new technique. 

The experimenters randomly assigned half of the participants to a “can’t” condition and the other half to a “don’t” condition. The “don’t” condition participants read about a program in which participants would be asked to say the following sentence whenever they felt a temptation to eat something unhealthy: “I don’t eat X.” They would fill in the tempting food for “X.” For the “can’t” condition, participants read about a program that worked in almost exactly the same way, but with a slightly different temptation response sentence: “I can’t eat X.”

At the end of the study, all participants were offered a snack as a reward for participating. Two options were available—less healthy chocolate candy bars or healthier looking granola bars. 

Study Results

Of the participants who chose a snack, 64% in the “can’t” condition picked a less healthy chocolate bar; the others picked the granola bars. For the “don’t” condition, only 39% of the participants who took a snack chose the candy bar. Just having people thinking about using the word “don’t,” seems to spur them to make healthier eating choices.

Other studies have confirmed this effect. Perhaps the best-known study was conducted with a group of participants who were already engaged in a healthy eating plan. 

The participants were asked to stick to their plan for 10 days at a time. Whenever they felt like eating something outside their plan, they were instructed to think or say a particular sentence to help them resist. 

The experimenters randomly assigned the participants to one of three groups. The “don’t” group used the sentence “I don’t eat X.” The “can’t” group used the same sentence, but replaced “don’t” with “can’t.” A third group, the control group, used an alternative sentence, “Just say no.”

The participants carefully recorded their eating for 10 days at a time. The measure of effectiveness used here was the number of days out of 10 that the participants managed to resist their problematic eating behaviors. 

The effects were very clear and statistically significant. The “don’t” group persisted for an average of 9.2 out of 10 days, while the “can’t” group only managed 2.9 out of 10 days. The “just say no” group persisted for an average of 5.2 days. Therefore, this study demonstrates the power of using language to tap into intrinsic motivation. 

Image of Professor Peter Vishton

Peter M. Vishton is an Associate Professor of Psychology at William & Mary. He earned his PhD in Psychology and Cognitive Science from Cornell University. Before joining the faculty of William & Mary, he taught at Northwestern University and served as the program director for developmental and learning sciences at the National Science Foundation.

This article was edited by Kate Findley, Writer for Wondrium Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for Wondrium Daily.