 Asakawa-Haas, Schiestl, Bugnyar, and Massen subsequently ran an open-choice experiment with eleven captive ravens in a group setting, using nine ravens from one group and two newcomers.They found that the ravens' decision which partner to cooperate with was based on tolerance of proximity and not on whether they were part of the group or not.The ravens in this experiment learned to wait for their partner and inhibit pulling the string too soon.