 In a later study with a mix of novices and experts, Suchak, Watzek, Quarles, and de Waal found that novices learned rapidly in the presence of experts, although likely with limited understanding of the task.Greenberg, Hamann, Warneken, and Tomasello used a modified apparatus that required two captive chimpanzees to pull, but delivered food to one ape first.They found that in many trials the apes who already had received a reward from joint effort kept pulling to help their partner obtain their food.