In order to adapt to a life spent paddling around in the ocean, the ancestors of dolphins traded in their nimble terrestrial appendages for sleeker fins and flippers. And yet despite the fact that they have no arms, legs or fingers to speak of, dolphins outclass even the most dexterous primate when it comes to one important test; understanding and producing pointing gestures. Even the cleverest of chimpanzees has difficulty understanding that a pointing finger is meant to direct someone’s attention to an object or event. Like most animals, a chimpanzee typically won’t look any farther than the tip of the outstretched finger, perhaps expecting a food reward to magically emerge from it. Dolphins on the other hand are easily able to follow a point to distant objects. What’s more, they appear to ‘get’ the meaning of a point the very first time they see one. At first glance, this does not make any sense: how can an animal without hands have evolved an ability to spontaneously interpret the meaning behind the human pointing gesture?
Some scientists have offered an intriguing explanation, and it all comes down to dolphins being exceptional listeners. Dolphins are able to produce a kind of biological sonar called echolocation: they can generate click sounds which bounce off of objects, resulting in click echoes. The information contained in these echoes gives the dolphin a mental image of the object. But here’s where things get interesting: if an eavesdropping dolphin happens to be swimming next to one of his friends who is echolocating on a mackerel, the eavesdropper will also be able to ‘hear’ the image of the mackerel emanating from the click echoes. So in a sense, the eavesdropper may be able to follow the echolocation beam of his friend to the mackerel in much the same way humans would follow a pointing finger.
In order to see if dolphins are in fact sensitive to the direction that each other’s echolocation beams are pointing, I have spent the last few years recording the behavior of wild dolphins using a special underwater video camera. By analyzing the dolphins’ behavior frame by frame as they echolocate on objects that they encounter, I’ve been able to track the subtle shifts in behavior that indicate that dolphins may indeed be eavesdropping on each other’s echolocation. Eavesdropping dolphins appear to remain silent and shift their heads to be aligned with their friend’s focus of attention.
The answer to the mystery may well be that dolphins, unlike chimpanzees and other primates, are immersed in a world of points – constantly following each other’s echolocation to find tasty fish, or alerting each other to the presence of dangerous sharks. The ability to understand a pointing gesture is no trivial matter, and is often singled out as a skill exclusive to the human mind; part of the unique arsenal of cognitive aptitudes that makes us the wise ape. One of the criteria used to diagnose autism in young children is to see whether or not they both produce and comprehend pointing gestures. Autism impairs the ability to put yourself in someone else’s shoes – to figure out what someone might be thinking; to mind read. Without a way to recognize someone’s intentions, or realize where they are focusing their attention, pointing is simply a meaningless, confusing signal; a mysterious wave of the hand. Autism makes it difficult to grasp the idea that other people have unique minds of their own that dictate their actions. Scientists believe that animals operate under similar, though not identical, limitations – unable to do anything more than read and interpret the behavior (but not the minds) of other beings. This may explain why, despite impressive intellectual aptitudes in other domains, most animals don’t get what you mean when you point them in the direction of their dinner bowl. As we begin to understand how pointing comprehension, mind reading skills, and echolocation may be interconnected in the dolphin brain, we ultimately learn more about the human brain. Somewhere at the intersection of the dolphins’ pointing skill and the limitations imposed by autism, lurks the answer to a bigger question about what makes us human.
(This essay took third prize in the 2008 Wellcome Trust and New Scientst Science essay competition)
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