Recently, Mendes, Hanus and Call [1] reported five orangutans repeatedly spitting water into a tube to retrieve a peanut that was floating at the bottom of the tube in a small amount of water. Releasing water from their mouths into the tube raised the water level and brought the peanut within reach. Additionally, control conditions demonstrated that spitting inside the tube was not a general response that subjects displayed upon encountering an out-of-reach reward. In particular, orangutans did not spit water into an empty tube upon encountering a peanut that was out of reach (in front of the tube). These data suggested that their spitting was goal-directed and performed to remove the peanut from the tube.
Peanut Of The Apes Sub Download
Furthermore, two elements suggest that this was a manifestation of insightful behavior [9], [15]: First, the sudden appearance of spitting into the tube after a period of unsuccessful attempts which did not involve spitting in any way and second, the immediate appearance of spitting when needed without reverting to previous unsuccessful behavior. Although the idea of insight has been criticized because prior experiences may have played a role in the solution, Köhler himself [9], [16] recognized that experience with objects preceded their insightful use. It is very likely that orangutans had multiple experiences with liquids in their mouths and even spat them at objects or other individuals. Moreover, orangutans were familiar with shelled peanuts and they might have even seen them floating in water. It is very likely that those experiences were instrumental in allowing subjects to solve the floating peanut task. However, the information gathered from those experiences still had to be cognitively reorganized/re-used to solve a problem that they had never faced before: a peanut at the bottom of a tube.
Nevertheless, orangutans using water to get a peanut from the bottom of a tube is a phenomenon that deserves further examination. From a comparative point of view, it is unknown whether other species of great apes would be able to solve the task. This information is crucial to making inferences about the evolution of cognitive flexibility in nonhuman primates and humans. It is also important to test other ape populations of the same species to see how widespread this ability is among other individuals within the species.
From a cognitive point of view, it is unclear whether apes would have also solved the task if the peanut had not already been floating in the water. It would seem that, encountering a dry tube with a peanut at the bottom is a more demanding task than encountering one with a floating peanut, because it requires thinking about water as a possible solution without having already seen it or its effect. Another aspect that requires further scrutiny is whether or not apes might have a general tendency to add water to the tube regardless of the presence of the reward. Although Mendes et al. [1] ran a series of control conditions to assess whether orangutans spat water indiscriminately into the tube regardless of the position of the peanut, more data would contribute to confirming their results. The aim of our study was to provide some answers to the open questions raised by Mendes et al. 's [1] results.
In Experiment 1, we tested chimpanzees and gorillas housed in the same facility as the orangutans tested by Mendes et al. [1], and used the same method. In Experiment 2, we expanded our sample by including two new populations of chimpanzees and orangutans living in sanctuaries in Uganda and Indonesia, respectively. In addition to the original test condition in which the peanut was floating in a small amount of water, we presented a condition with the peanut lying at the bottom of a completely dry tube. Furthermore, successful subjects were presented with a series of control conditions to investigate whether or not subjects added water only when it was required for solving the task.
In Experiment 4, we tested the ability of 4-, 6-, and 8-year-old children to solve the floating peanut task in an experimental setting analogous to that presented to the apes. We recruited relatively older children because the demanding task requires a great deal of innovation and creativity. Like the apes in Experiment 2, half of the children received the condition in which the tube was quarter filled with water and half of them received the condition in which the tube was empty.
The goal of this experiment was to investigate and compare the performances of chimpanzees and western lowland gorillas with those of the orangutans tested in Mendes et al. 's study [1]. As in the original experiment, the task required subjects to retrieve a peanut from inside a Plexiglas tube by collecting water from a dispenser and then spitting it into the tube in order to make the peanut float and bring it within the subject's reach.
Each subject received a total of eight trials (one trial per day). Each trial had a maximum duration of 20 minutes. The first 10 minutes were standard, meaning that all of the subjects received that exposure time regardless of their motivation or effort. The trial ended if the subjects retrieved the reward earlier. If the subject was still working to get the peanut after 10 minutes, the experimenter (E) allowed an additional 5-minute period. Again, if the subject retrieved the reward or lost interest, the trial was terminated but if the subject remained interested in the task, it continued for additional 5 minutes. Consequently, each subject had a maximum of 20 minutes per trial to solve the problem and obtain the reward, provided that they showed continued interest during the trial (see Figure 1). E provided no specific cues on how to solve the task and was only allowed to knock on the tube or call the subject's name in order to gain its attention.
The discrepancy between the chimpanzees' and gorillas' performance in the current study and the orangutans' in the Mendes et al. study [1] is striking. After eight trials, none of the apes in the current study added water to the tube, whereas all five orangutans solved the task from the first trial onwards. It should be stressed that all three ape species were housed under the same conditions at the same facility (WKPRC, Leipzig), and the apparatus and the procedure were identical for all apes. Given that chimpanzees are thought to be especially skillful and innovative problem solvers (e.g., [9], [23]), the current findings are all the more puzzling. The comparatively small sample size involved in the reported studies may have contributed to these discrepant results. In particular, it is unclear whether the observed differences between orangutans on one side and chimpanzees and gorillas on the other side reflect a genuine interspecific difference in problem-solving abilities or whether they represent a mere sampling artefact. In the next experiment, we took up this question by testing other samples of orangutans and chimpanzees on the floating peanut task.
Another outstanding issue in the original Mendes at al. study [1] is whether or not the presence of water inside the tube influenced the orangutans' behavior. In other words, how crucial is seeing a floating peanut to solving the task? Although Mendes et al. [1] included control conditions that addressed this issue by using an empty tube, these conditions were conducted after the experimental condition. Once subjects had solved the problem with the floating peanut, they also succeeded when the tube was dry, which suggests that seeing water was not necessary for producing a solution or else it could have been due to a carry-over effect of the earlier study. And so, it is unclear whether subjects would be able to solve the task without initially seeing any water inside the tube. We addressed this issue in the next experiment.
The first goal of this experiment was to test one additional sample of sanctuary-housed chimpanzees and orangutans to confirm the observed differences between the chimpanzees and orangutans housed in Leipzig. The second goal of this experiment was to investigate whether apes were able to solve the task when seeing the peanut at the bottom of a dry tube rather than floating in water. Half of the subjects received the original test version with a quarter-filled tube and a floating peanut, whereas the other half was confronted with a dry tube and a peanut lying at its bottom.
The peculiar behavior of two chimpanzees is worth mentioning: One adult female chimpanzee was successful during her first trial and continued to spit water into the tube for one more trial (but without getting the reward). She finally stopped spitting entirely from the third trial onwards. One juvenile male chimpanzee (dry-condition group) solved the problem during the first trial but failed to add enough water to reach the peanut in the following trials. He spat water during two more trials but had severe difficulties in channeling the water into the small opening of the tube and finally lost interest after several (4) unsuccessful attempts. We decided to present him with the wet condition but he still did not manage to add enough water during the first two trials,. However, when the amount of water inside the tube was increased (to half filled) he finally spat enough water (to reach the peanut) and continued to solve the problem from the third trial onwards throughout the five remaining trials. It seemed that even though he had already found the solution during the very first trial, he simply failed to master the appropriate spitting technique, which caused him to give up. Because less water is needed to solve the task in the wet condition, he was once again motivated and succeeded up to the end of the experiment.
In addition to the five successful subjects, four other individuals spat water into the tube but failed to complete the task; in other words, they did not add enough water to bring the peanut within reach. One of them (a male) belonged to the dry-condition group, and three of them (two males, one female) belonged to the wet-condition group. On average, those four unsuccessful subjects spat water (at least once) in 41.8 percent of all trials. 2ff7e9595c
Comments