An international pair of researchers, Ulrich Schimmack of the University of Toronto and Richard Lucas of the University of Michigan, have conducted a study on the long-term happiness of married couples that may have profound implications for our understanding of what makes people happy in long-term relationships.

The fundamental debate that exists over happiness is whether it stems from internal factors (e.g., genetics or biological factors) or from external factors (income, social relationships). These researchers followed more than 800 German married couples over a period of 21 year period. An innovative statistical analysis indicated that individuals’ reports of life satisfaction closely matched those of their spouses.

More specifically, they found that spouses were similar across times when there were rapid fluctuations in satisfaction level, as well as when there were gradual changes in satisfaction across time. There was also similarity in the general level of life satisfaction that is generally stable across time.

There is strong support for the presence of a strong genetic component in life satisfaction. However, if one were to assume that all of life satisfaction were genetically determined the finding of similarity in satisfaction, even during times of change, would have profound implications for the genetics of relationship satisfaction. For couples to change consistently on a genetically predisposed behavior couples would not only have to seek out mates who are highly similar to themselves on personality factors underlying life satisfaction, they would also need to find spouses with whom they share a high degree of genetic similarity.

Could it be that the end result of assortative mating is genetic similarity? This largely unexplored territory may be the next logical step in understanding why similarity on personality dimensions is a strong factor in predicting long-term relationship satisfaction. While it is likely there will be some degree of gene environment interaction in the prediction of long term relational satisfaction, evaluating the impact of genes on life satisfaction could be a critical factor in better understanding the complexity of compatibility.

Further Reading:

Schimmack, U., & Lucas, R. E. (2006). Marriage matters. Spousal similarity in life satisfaction. Discussion papers DIW Berlin.

http://www.google.com/search?q=marriage+matter+similarity&hl=en&sourceid=gd&rls=GGLD,GGLD:2006-50,GGLD:en