According to a Harvard Business School study led by Michael Norton, people optimistically interpret ambiguous information and assume they will get along. As we learn more, our thinking is less forgiving.
The research examined the differences in opinions before and after dates arranged online. Before the date, when participants knew less, prospective dates were rated between 6 and 10 on a 10-point scale, and no one scored below 3. After the date, average scores were lower, and ones weren't uncommon.
Norton says that "people are so motivated to find somebody they like that they read things into the profiles." When a man writes that he loves the opera, his would-be mate imagines dressing to the nines to see the Met but when she learns more, she discovers "opera" refers to singing in the shower. "Once you see one dissimilarity, everything you learn afterward gets colored by that," Norton says.
I'm waiting for the next study on couples to see if instead of communicating better they worked hard to maintain ambiguity.