I'm trying to describe this personality trait/behaviour that someone demonstrates. Consider this situation; while a group of colleagues hangs out at a bar, someone suddenly suggests a lottery group play where everyone puts in a small amount of money. While everyone willingly participates, one person refused and opted out of the play.
What are some ways of describing this particular person's behaviour and/or the personality trait that this person possesses? Obviously he's cheap, but leaving money aside, I'm trying to describe his behaviour/trait with emphasis to the negativity and fact of him not willing to act with the group.
Another example maybe, if the group of colleagues suddenly decides to go bowling and the same individual opted out again because he dislikes it greatly. Not all the rest of the people in the group likes bowling but they go anyways. What quality is this individual lacking? And what are some ways of describing this kind of behaviour and personality trait?