I'd appreciate it if you could tell me the meaning of "common interests" in the following sentences.
"In addition to social mobility, social mobility also plays a role in differences in friendship patterns between Germany and the United States. Americans tend to form friendships on the basis of common interests, and because Americans tend to define their identities mere in terms of occupation than do Germans, work-related interests often determine whom Americans socialize with. As a person's job or position changes, so do that person's interests, and consequently, social circle. In the U.S. friendships tend to form in "large, loose networks of people. Phrases such as "my friend from work," or "my bowling friends" describe these wide, relaxed networks of friends."
"Interests" can mean "things that you enjoy doing" or "things that bring advantages to someone or something." I first thought "social interests" in the first sentence has the former meaning, because it says "my bowling friends" and "these wide, relaxed networks of friends" in the last sentence. However,
the second sentence says "work-related interests," and the third sentence says that a person's interests change when his/her job or position changes (It seems to me that changing jobs does not always change what a person likes to do, which makes me feel that "interest" here has the latter meaning or something like "involvement."
But then, the third sentence may simply mean that when people change jobs, they tend to like what their new coworkers enjoy doing. If this is correct, "interests" means "things that you enjoy doing."
Could you tell me which interpretation is correct? Could you also tell me how to paraphrase the expression "common interests" in the passage?
Thank you very much.
Takashi