When I was in my teen years, I also tended to asociate with adults more than with my peers. This was easy, because I was growing up in local authority care and of course, there were adults running the places I stayed in.
Even in the community home where I stayed apart from one person I hung around with - we were both mad on Science Fiction, the Paranormal, etc - I used to either be on my own a lot or associate mostly with the members of staff.
I tend to find that the 'peer group' are, or at least seem to be, the most threatening of all the possible groups, because that is the benchmark against which you can be measured.
Staff and other adults are less judgemental, as someone said earlier, so it means there is no need to put on an act. Also, the quality of conversation tended to be far higher with adults than with peers.
Imagine my amazement when, upon becoming an adult, I noticed that the quality of conversation was not that high (ie, it wasn't about things that interested me) because at this point the adults would not indulge me in my subjects of interest.
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"The power of accurate observation is called cynicism by those who have not got it." - George Bernard Shaw (Taken from someone on comp.programming)