Players always determine a RCM’s reaction to a social situation.

If the social situation can be role-played, that is always preferable to rolling dice.

The cast are almost always strangers in strange lands, and sometimes the reactions of people to teenage superheroes from another time isn't obvious. If you need a tie-breaker, have the player roll dice+CH. The higher the roll, the better impression he just made on the local.

If the characters involved have opposing interests, this is a contested check. Very often, this is one character (the RCM) trying to convince someone of something. Both roll their dice. If one character beats the other’s roll by the losing character's base dice or more, he gets his way. Short of that, the conflict continues.

A few considerations:

• Arguments about logic can use IQ instead of CH. We should note that these sorts of arguments are by far the exception among human society.
• Arguments based on anything else (which is most of them) use CH.vs CH
• For an attempt to bamboozle, trick, con or other dishonesty, use CH vs IQ.
• For a bribe, use CH vs WP.
• For attempts to threaten or intimidate, use CH vs CO. Size may matter as well.