It seems like the recipe for a perfect friendship or relationship: you both buy organic products, you both exercise outdoors, and you both eat mediterranean food. Every day we make decisions about what brands to buy, what clothes to wear, or what entree to order. Often, we'll ask someone else for their opinion - so what would be better than to have a friend or partner who shares your tastes? It turns out that agreement isn't everything. While it is important that you share an opinion with your friend, it turns out that the why you like something might be more important. If you like things for different reasons, rather than reassure you, the agreement might undermine your confidence. If you like organic products because you are concerned about the environment and your friend buys those products because she thinks they are healthy for her, it might be a recipe for self-doubt and changes of opinion.
Researchers Cait Lamberton, Rebecca Naylor, and Kelly Haws, from the University of Pittsburgh, Ohio State University and Texas A&M, recently investigated the importance of sharing the same reasons for opinions in a series of studies published in the Journal of Consumer Psychology. They focused on what is called "choice confidence", which is related to greater satisfaction with a particular choice. They found that when people two people shared an opinion, but for different reasons, their confidence in that opinion is undermined. For example, in one study, students were asked to make a hypothetical choice between two different graduate schools and asked to rank their reasons for their choice. Then, they were told they would be completing a task with a partner, and under the guise of getting to know their partner, were shown their partner's choice and ranking of reasons. In one set of conditions, this fictional partner made the same choice for the same or different reasons. In another set of conditions, the fictional partner made a different choice for the same or different reasons. Then, participants were asked to report their confidence in their original choice.
In the cases where the partner made a different choice, the reasons for that choice did not affect the participant's confidence. Simply put, it didn't matter while people disagreed. In the cases where the partner made the same choice, the reasons for that choice significantly affected the participant's confidence. Participants were most confident of their ideas when the partner made the same choice for the same reasons. However, when the partner made the same choice for different reasons, participants felt reduced confidence. This same effect was found for voting choices and vacation choices.
What does this mean for our relationships? For one thing, it suggests that sometimes finding common ground is easier if we stick to shallow understandings - as long as you and I agree, we'll get along fine. But, when it comes to important decisions, and perhaps decisions where factions are in disagreement, it would be best to probe the reasons behind opinions. Understanding that even those who agree with you are different may make people more likely to compromise and change their opinions. For instance, as Republicans find that some members are elected because of their socially conservative viewpoints and others are elected because of their fiscally conservative viewpoints, the party itself may become able to change and adapt to a changing electorate.