|This article relies largely or entirely on a single source. (April 2012)|
Convergence suggest that when people get along with each other for a long enough time, their act, thinking, and even appearance will becoming more alike as the relationship progresses.
However, as regards certain personality traits, like the degree of introversion or of sourness, there was research carried out by psychologists at Michigan State University and the University of Minnesota, based on a relatively huge data base of 1,296 couples who have been married for an average of 19.8 years, suggesting that only the degree of aggressivity actually tended to converge.
What they found is that couples who had been married for a long time -- up to 39 years -- were no more alike in fundamental personality traits than newlyweds, leading the researchers to conclude that personalities do not grow more similar as the years pass. More likely, the couples were looking for specific traits during the courtship and they ended up with someone who was very much like themselves.
(Features such as the acts, thinking, and appearances of the spouses were not directly investigated.)