My experience is more that 4-5 is optimal, and groups splinter into 3+3 at 6. It could be because I'm an introvert and tend to hang out with other introverts,

My experience is more that 4-5 is optimal, and groups splinter into 3+3 at 6. It could be because I'm an introvert and tend to hang out with other introverts, though. A group of 5 will usually have 2-3 people actively talking and 2-3 listening and occasionally contributing only if they have something worthwhile to say. 5 extroverts, in my experience, are unmanageably loud and will usually split into 2+3. Note the sample bias in this. If you're studying social gatherings, introverts tend to disproportionately not attend these, because they are energy-draining. If you are an introvert, however, then any gathering you are part of will by definition have at least one introvert in it.