Can You Tell the Difference Between Regular Coffee and Decaf?

There’s a Cosmo article from 2014 that haunts me to this day. It wasn’t the one where Miley Cyrus offers sex advice or even the one about the notorious doughnut tip. It was an interview with an anonymous Starbucks barista, who revealed—boasted, really—that if a customer rubbed her the wrong way, she would let herself get confused between the decaf and the caffeinated buttons on the espresso machine and intentionally mess up their order.

I’d far rather skip my morning cereal than go without (two cups of) (caffeinated) coffee. I’m not alone: For many Americans, breakfast is as much about coffee as it is about pancakes or Pop-Tarts. Coffee may have even played a role in making breakfast into a socially acceptable meal. In the Middle Ages, eating before midday was seen as gluttonous and indulgent, according to Heather Arndt Anderson’s Breakfast: A History. It was only when coffee arrived in Europe in the 17th century, allowing breakfasters to swap ale for a productivity-enhancing beverage, that the Church finally came around on the idea.

Today, nearly two-thirds of adults in the U.S. rely on coffee to get them going, according to a recent Gallup poll. But what would happen if they were duped into drinking decaf? If the Cosmo barista’s hapless victim were unaware that she were getting decaf, could she actually derive the same psychological and cognitive benefits as she would from her usual morning coffee?

Research suggests that she might.

In 2007, Laura Juliano, a researcher at American University, discovered that decaf could effectively offset the symptoms of caffeine withdrawal—at least for a while. Juliano invited about 90 people into her lab for a cup of coffee. Afterward, she instructed them not to consume any caffeinated beverages or foods until she gave them permission. The next morning, the volunteers returned to the lab, where they were divided into four groups. One group was given a cup of caffeinated coffee; another group was given decaf; a third group was told they were getting caffeinated coffee, but really received decaf; and a fourth believed they got decaf, but actually received caffeinated coffee. Forty-five minutes later, everyone answered questions about their caffeine-withdrawal symptoms—headaches, fatigue, irritability. Unsurprisingly, the group that knew they’d had coffee felt fine, and the people who knew they were drinking decaf felt lousy. But the surprise came when Juliano analyzed the data on the other two groups. The people who falsely believed they were drinking decaf reported more severe caffeine-withdrawal symptoms than those who drank real coffee but thought they’d had decaf. The placebo effect had its limits, though. Juliano invited her subjects back to the lab that evening for a final visit. By this point, biology had overtaken psychology: Everyone’s symptoms were more or less appropriate to the amount of caffeine they had actually consumed.

Another study, this one from psychologists in China, looked at whether a placebo pill could prolong the benefits of caffeine—or, in real world terms, whether you could replace a second cup of coffee with decaf. On five separate occasions, ten men were deprived of sleep for 28 hours and then given a caffeine pill. Four hours later, they received a second caffeine pill, a placebo or nothing. It turned out that the sugar pill could extend the cognitive benefits of the first dose almost as effectively as a second caffeine pill.

The most persuasive research comes to us from a 2011 study in the journal Appetite. A team of psychologists at the University of East London recruited 88 regular coffee drinkers to come to the lab. Some were given regular coffee; others got decaf but were told it was caffeinated; some knowingly drank decaf; and some thought they were drinking decaf, but actually received caffeinated coffee. About an hour later, the volunteers filled out a survey on their mood and did tasks—like sorting cards—to test their reaction times. The group that falsely believed they had consumed caffeine showed almost as much improvement in their performance as the ones who had actually had coffee, and rated their emotional state as less “dejected/depressed” than the ones who knew they had been given decaf. (They were even in a better mood than their peers who were told they were getting decaf but actually received caffeine.) The findings “add to the growing body of evidence that highlights the importance of psychological variables over pharmacology,” the authors wrote.

Thanks, science: I'm now marginally less disturbed by Cosmo’s “Confessions of a Starbucks Barista.”