I'm not sure Extroversion/Introversion is related to prosocial behavior in any direct way. Prosocial always refers to cooperation, fairness, and acting on behal

I'm not sure Extroversion/Introversion is related to prosocial behavior in any direct way. Prosocial always refers to cooperation, fairness, and acting on behalf of society as a whole. IOW prosocial is the opposite of self-interested, not the opposite of shy. We know that psychopathic, anti-social people (ie the dark triad types) score very high on extroversion. They direct their energy outwards to manipulate others - the polar opposite of "prosocial". Shy introverted people low on the extroversion scale also demonstrate lower prosocial behavior on average, mostly through avoidance. The most introverted and the most extroverted people are thus equally likely to engage in anti-social behavior (though qualitatively different, both ends of the spectrum are looking out for #1)