Apes prove to have unique human quality

Photo credit: The NY Times

Photo credit: The NY Times

By Emma Gruner, Staff Writer

The family of great apes, which includes chimpanzees, orangutans, bonobos, and gorillas, has long been a source of great fascination to evolutionary scientists. As humankind’s closest relatives in the animal kingdom, they have served as a bridge between the world of man and beast. Psychological studies conducted on these creatures have gradually revealed their remarkable intellectual abilities, and they have made scientists constantly reevaluate their answer to this question: what separates humans from animals? The most recent study was published on October 6 in Science, and it suggests that apes may possess what psychologists call “theory of mind”.

Theory of mind is defined as the ability to attribute desires, intentions and knowledge to others. A classic experiment to test this ability in young children is to have them watch an actor hide a chocolate bar in a box. After the actor leaves, a second actor arrives and hides the chocolate bar elsewhere, and the children are asked where the first actor would look for the bar. A child who answers “in the original box” is shown to possess theory of mind; they understand what is going on in the first actor’s mind, even though it does not match reality.

Over the past several decades, many studies have been conducted to investigate whether great apes possess theory of mind or not. In these studies, the apes have shown remarkable powers of perception; they can deceive, they can recognize the motives of others, and they can remember helpful partners from collaborative exercises. However, these apes have consistently failed to detect false beliefs, and this leads scientists to conclude that theory of mind was a unique human ability. According to Brian Hare, an evolutionary anthropologist at Duke University, “Testing the idea that nonhuman [animals] can have minds has been the Rubicon that skeptics have again and again said no nonhuman has ever, or will ever, cross.”

Yet these non-humans did cross it, according to the most recent Science study, evolutionary anthropologists Christopher Krupenye of Duke University and Fumihiro Kano of Japan’s Kyoto University co-led the study. The study used eye-tracking technology to study the reactions of thirty great apes – fourteen chimpanzees, nine bonobos, and seven orangutans – as they watched a dramatic confrontation play out before them. In the scene, an actor in an apelike costume, nicknamed King Kong, steals a rock from another actor, hides the rock in a box and scares the man away. While the man is gone, King Kong moves the rock to a new box. King Kong changes his mind and carries it out of sight. The man then returns to search for the rock. At this point in the video, twenty-two of the thirty apes looked directly at the two boxes, and seventeen of the apes stared at the box where the rock was originally hidden. Similar data was obtained when a group of forty apes watched another, slightly different scene. These results suggest that the apes knew that the man would search for the rock in its original location, even though they themselves knew that the rock was no longer there.

These findings came as a great surprise to many in the scientific community, especially since great apes have never shown such sophisticated abilities in prior studies.  This discrepancy may be attributed to certain aspects of the experimental design, in which Krupenye and Kanyo were careful to eliminate as many distractions as they could. For example, the King Kong actor was careful to carry the rock off the scene after removing it so that the apes would not be tempted to convey their own beliefs about the rock’s location. Similarly, the researchers deliberately designed an experiment that did not involve food, so the ape’s perception would not be affected by their self-control. As Kuprenye states, “they only have to remember something that just happened; they aren’t weighed down by other cognitive demands.” These precautions suggests that the study’s results may be more accurate than those obtained by other, less straightforward experiments.

However, animal psychology is a complicated field, and many are still hesitant to accept these findings as definitive proof that apes have theory of mind. Laurie Santos, a cognitive psychologist at Yale University, is still inclined to trust the myriad of past studies that have indicated the lack of this ability in chimps and other primates. She claims that even if the apes in this study were aware of the man’s ignorance of the rock’s location, they were not necessarily aware of his false expectations on where to find it. Amanda Seed, psychologist at Scotland’s University of St. Andrews, says that the experiment’s findings were unclear about whether the apes truly understood that the rock was gone from the first box.

She suggests a follow-up experiment that would test whether the apes were surprised at finding the object in its original location. And according to Valerie Kuhlmeier,  a developmental psychologist at Canada’s Queen’s University, the apes may have been relying not on true theory of mind but simply the knowledge of abstract rules – in this case, the tendency of people to look for objects in the places they last saw them. The fact that the apes understood this general behavioral trait does not mean they genuinely grasped the concept of false belief; this ability, many believe, is still restricted to humans.

Ultimately, this study has still sparked the interest of the scientific community, and further research and development opportunities are already being discussed. For Kuprenye, this will likely involve an experiment to test whether apes are capable of acting on their knowledge of false beliefs. An ape’s ability to, say, hide food from others by relying on their comrades’ mistaken impressions would reveal an entirely new level of sophistication to their communities. Furthermore, the eye-tracking technology utilized by the experiment could be altered to observe the reactions of other species like birds, cats, and dogs. Such developments would take the research of animal psychology to an entirely new level. In the words of Brian Hare, “Now the fun begins!”

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