Commonalities may be comfortable, but they also create blind spots. You want lieutenants who provoke feuds and dissent.
Couples tend to look like each other. Some people seem to look a lot like their pets. Such observations are a common source of jokes and jibes but inside them lie an important truth: Our brains prefer the familiar.
Statistically you are most likely to choose partners who look a lot like you. They’ll also share your tastes and values. However much you may pride yourself on being wild and eclectic, each of us represents a pattern that some other people quite closely approximate, and these are the people we tend to like. Our brains are very similar to Amazon’s recommendation engine or eHarmony’s dating profiler.
The reason for this is familiar information is prioritized by our brains. Known information doesn’t need to be considered or scrutinized so it reaches our consciousness more quickly. This is highly efficient, a form of load balancing. We deal with the easy stuff first.