My sim doesn't currently any levels of the charisma skill. I didn't even know that was a possible skill until I happened to read about it here in the skill guides (started playing recently). I've been playing for several sim weeks now, and I socialize with other sims on a regular basis. I don't understand why I haven't attained at least a few levels from these numerous conversations. I'm aware of the acquaintance/friend thresholds, and I think I have plenty to satisfy the first few levels. Probably have at least a dozen acquaintances and 3-4 friends.
Since I didn't know this was a skill, I wasn't going out of my way to learn it. Do I have to get the skill started by reading or talking to a mirror before talking to other sims will count?