The traditional American breakfast is a high-carb affair, with its heaping dishes of pancakes, waffles, toast, cereal. It may affect not just our waistlines, but also who we are.
In a recent study at the University of Lübeck in Germany, scientists asked participants about what they ate in the morning, then had them play the “ultimatum game” — a common experiment that measures how much people tolerate unfairness. In essence, they were trying to test whether human behavior is subject to a well-known cliché: Are we what we eat?
“We wanted to know whether our decision-making or thoughts might depend on what we’ve eaten,” said So Young Park, a professor of social psychology and neuroscience at the University of Lübeck. “We eat three times a day. And you can imagine that, if we change our behavior depending on our food, that would be quite striking information.”
The ultimatum game puts study participants in an uncomfortable scenario. Players A and B are told that there is $10, but Player A must decide how the money is split between them. Scientists asked their study participants to act as Player B and watched how they reacted to lopsidedly unfair offers, such as being offered $1 out of $10. Study participants were told that, if they decided to reject an offer, neither person would take home any money at all.
In theory, “the respondent should accept any offer greater than zero, no matter how small, because it’s better than nothing,” said Tobias Kalenscher, a professor of comparative psychology at the University of Düsseldorf. “But respondents often would rather have nothing than live with an unfair deal.”
Though even a $2 offer could mean a nice doughnut for the next morning, scientists found that participants with high-carb breakfasts rejected unfair offers 40 percent more often than those with high-protein breakfasts.
“We could see a very tremendous difference in these people,” Park said. In a second experiment, breakfast was fed directly to study participants before they played the ultimatum game. Scientists found similar results, as well as differences in participants’ blood samples.
“High-carb people had lower tyrosine levels. And the lower the tyrosine levels, the higher the rejection rate,” Kalenscher explained. Tyrosine is an amino acid that acts as a precursor for dopamine, a neurotransmitter that plays a significant role in our brain’s reward system. But this connection doesn’t mean that we should clear out our cupboards and start anew with high-protein, low-carb diets.
“You can say that people with high rejection rates are just sensitive to unfair treatment,” Kalenscher said. “It’s absolutely not a bad thing.”
The point is that “food dictates your choices,” Park said. “Depending on what you have eaten, your choice is being dramatically modulated — that is what we’re showing. You should really try to have a balanced diet.”
Kelly Kasulis is a freelance journalist. Follow her on Twitter: @KasulisK.