Humans are able to collaborate on projects to accomplish their goals. What about chimpanzees? Do chimpanzees know when they need to recruit help in order to solve a problem and when they are able to solve it on their own? Researchers placed a food platform outside of the chimpanzee’s cage. They threaded a rope through metal loops at either end of the platform with the rope ends extending into the cage. If the chimp pulled on only one rope, it would unthread through the platform and the chimp would not be able to get the food. If both ends of the rope were pulled simultaneously, the food platform would move toward the cage and eventually the chimp could reach it. Two different conditions were presented to eight chimpanzees. In the collaboration condition, the food platform was wide enough that one chimp couldn’t reach both ends of the rope at the same time to successfully pull the food platform toward them. They needed to recruit another chimp to pull one end while they pulled the other. In the solo condition the food platform width was such that a single chimp could reach both ends of the rope and unassisted successfully pull the food platform to the cage. For both of these conditions there was an adjacent cage containing another chimp available to help solve the problem. The test chimp had the ability to unlock a sliding door to let the other chimp into their cage to assist them in the retrieval of the food platform. Each of the eight chimps performed several trials of each condition. Data were gathered as the percentage of trials the test chimp opened the door to the adjacent cage for each of the two conditions. Are chimps more likely to recruit a collaborator in the collaboration condition than in the solo condition? (Use data Chimps.)
a. State the null and alternative hypotheses.
b. If you compared the average percent of trials the cage was opened in the collaborative condition to the average percent of trials the cage was opened in the solo condition, what piece of information are you ignoring? How would this affect your analysis?
c. Carry out a randomization analysis of these data to see if chimps are more likely to collaborate in the collaboration condition than in the solo condition. Remember, the same chimp is performing in each of these different conditions.