Eureka! Science has discovered the key to a happy marriage. Or, well, something like that. A study published in April's Personality and Social Psychology Bulletin followed couples over four years to track their relationship satisfaction. The results are enlightening, if not exactly a recipe for happiness.Florida State University Professor James K. McNulty surveyed 135 newlywed, mostly white, couples in their 20s, with a combined income of less than $40,000 in Tennessee, according to New York magazine. They were asked to measure the standards for their marriages in categories such as caring, support, and independence, Science Daily reports. They were also asked about their marital problems and level of satisfaction in their relationship while participating in videotaped marital discussions. Then, over the next four years, they answered a questionnaire about their marriage every six months.McNulty's conclusion boils down to this: The couples who had high expectations of their relationships and who fulfilled those expectations were satisfied with their marriage. Those who had high expectations and didn't fulfill them were not satisfied — which seems pretty obvious. Those who had low expectations that were fulfilled were actually pretty satisfied, too. Ergo, the key to being satisfied is to know in advance how much to expect.