8b609377_Atlas_gestures___Portal_Wiki__How_To_Unlock
[Name] Rock Paper Scissors [Description] Can only be performed when Atlas is near P-body. If one of the bots decides to play a game of Rock Paper Scissors, the other one will take part in it too. Depending on the outcome, the bots will react to it by cheering or showing disappointment. [How To Unlock] 
Complete the fourth chamber of the Team Building Course.
Atlas gestures - Portal Wiki
How To Unlock