Coke or Pepsi? Partner's choices can make you miserable

"People think compatibility in relationships comes from having similar backgrounds, religion or education," said Gavan Fitzsimons, a marketing professor at Duke University's Fuqua School of Business. "But we find those things don't explain how happy you are in life nearly as much as this notion of brand compatibility."

The findings, "Coke vs. Pepsi: Brand Compatibility, Relationship Power, and Life Satisfaction," were recently published in the Journal of Consumer Research. Fitzsimons worked with Fuqua colleagues Tanya Chartrand and Grainne Fitzsimons, plus lead author and former Fuqua PhD student Danielle Brick, now at the University of New Hampshire.

The researchers found that partners who had low power in their relationships -- those who don't feel they can shape their partner's behavior -- tend to find themselves stuck with their partner's preferred brands.

"If you are lower in relationship power and have different brand preferences than your partner, you're probably going to find yourself stuck with your partner's favorite brands, over and over again. This could lead to a death-by-a-thousand-cuts feeling," Brick said. "Most couples won't break up over brand incompatibility, but it leads to the low power partner becoming less and less happy."

Studies in several settings produced the same result. The researchers used brand preferences in soda, coffee, chocolate, beer and automobiles to study individuals and couples, some of whom were tracked over two years. These results were combined with findings on relationship power and happiness.

"It's an extremely robust effect, we found it over and over and over again," Fitzsimons said.

Brick said it's likely these brand compatibility effects have steadily gained strength as brands have evolved to play a bigger role in the daily lives of consumers. But they aren't given the same weight as other relationship-influencing factors because they're not seen as significant.

"If you are a different religion than your romantic partner, you know that if this is an issue you can't work through, then the relationship isn't going to last," Brick said. "Conversely, if you like Coke and your partner likes Pepsi, you're probably not going to break up over it -- but 11 years into a relationship, when he or she keeps coming home with Pepsi, day in and day out, it might start to cause a little conflict. And if you're the low-power person in the relationship, who continually loses out on brands and is stuck with your partner's preferences, you are going to be less happy."

The results have implications for individuals and firms.

"People who are looking for love should maybe consider including brand preferences on their dating profiles," Fitzsimons said. "There's also an opportunity for marketers to seek to be the family brand. Even if two partners have slightly different brand preferences, if they can adopt a joint brand that both are happy about, that might increase happiness for a partner who would otherwise feel unsatisfied."

Fitzsimons said that family branding isn't currently commonplace.

"Some brands are marketed as family-oriented, but that's not the same as reaching out to everyone in the family," he said. "It's tricky, but firms that get it right can have their brand associated with happiness and harmony -- and there's nothing better than that."