Over the course of the last decade, many games have shifted from single player to shared social experiences. Yet, most research examining antisocial behavior has focused on coded content and ignored the influence of other players. This paper examines the influence of the behavior of another player on strategy selection, and the formation of expectations, enjoyment, frustration, and state aggression. It reports an experiment examining antisocial griefing behavior in the multiplayer game Neverwinter Nights, where observational learning, revenge seeking, and expectation formation are tested. The results show that (a) the first encounter that a player has in a game shapes both behavior and expectations; (b) environments that facilitate expectation of cooperation will lead to retaliation against players who grief, whereas environments that facilitate expectations of griefing will increase the frequency of griefing, but not the frequency of retaliation against players who grief; and (c) griefing decreases enjoyment, increases frustration, and increases state aggression for the recipient.