Scientists have discovered that there is one thing above all else that determines the lasting power of a friendship. Many people guess that it is the ability to communicate that determines the quality of a friendship. In actuality, studies have shown that friends who have the most fun together are most likely to stay together. Fun is a difficult word to define and yet we know when we are having it. It is a difficult thing to predict and yet there are some friends that we have fun with almost every time we get together. Fun is the key factor in a lasting friendship.