04 June 2007

Dolphins get the point


You may recall from The Dolphin Pod episode titled “Herman’s Dolphin Prodigies” that dolphins have proven themselves to be capable of understanding the human pointing gesture. Dr. Louis Herman and his research team have shown that dolphins, when given a pointing arm and finger gesture to indicate an object, understand that this gesture is a cue to the location of an object. This might sound like a very boring, elementary skill, but the ability to follow a pointing gesture is very rare in the animal kingdom. Even super smart animals like chimpanzees have a very hard time with pointing comprehension.

If you have ever tried to train a dog, you likely noticed that a pointing gesture often results in the dog looking at the end of your finger, and not necessarily in the direction your finger is pointing. This is the typical kind of response that most animals will have to a point. In experiments where researchers try to use a pointing gesture to indicate an object for monkeys and apes, the point usually only works if the object is placed very close to the finger tip – not exactly the same thing as understanding the true human ‘meaning’ of a point. The animal may also just follow the direction of movement of the reaching arm and finger and so find their way to the object by accident.

Dogs, unlike most animals, can be taught to reliably use the pointing gesture as an indication of the location of far away objects. This rare ability has been attributed to their long history of domestication – researchers think that humans might have selectively bred dogs to understand pointing. Dolphins, on the other hand, are not domesticated animals, so their ability to understand pointing must then be attributed to some other cause. Concerning pointing comprehension in dolphins, researchers have made the following startling discoveries:

  1. Dolphins are able to understand pointing without being explicitly trained
  2. Dolphins can understand the pointing gesture even if they don’t see the arm move – the form of the point by itself is enough information, not the motion
  3. Dolphins can understand a variety of pointing forms, including pointing straight out to the side, and across the opposite side of the body
  4. Dolphins understand how to use the pointing gesture the very first time they are tested

Why are they able to do this? And how on earth is a dolphin able to understand a human point when they don’t even have hands or arms themselves?

Researchers Dr. Adam Pack and Dr. Lou Herman provided a variety of possible explanations for this striking ability, including the idea that dolphins must be keenly aware of the social cues of other dolphins because of a need to navigate the complex social situations that are found in dolphin society. Being able to read the behavior of other animals - sensitivity to their focus of attention – may be a common dolphin ability. By figuring out what the other guys is looking at, and guessing as to what he is intending to do, you have a better chance of getting a leg up in the dolphin social hierarchy (or maybe I mean a fin up). Human pointing may be easy for a dolphin to figure out because of their sensitivity to these cues for attention among their peers.

But there is one other explanation that is even stranger and may explain exactly why a dolphin is able to work out that a pointing arm is a reliable indicator of where an object is located. It all has to do with echolocation. The idea works likes this: if a dolphin is able to perceive the outgoing echolocation beam of another dolphin, it will know exactly where that dolphin is ‘looking’ with her echolocation. The outgoing beam then forms a kind of analogy to the human pointing arm. And, since dolphins are used to perceiving the echolocation beam of other dolphins as they go about their daily lives, they may be able to automatically understand the human point as something equivalent to an outgoing beam.

What makes this an even stronger association is what happens to the echolocation beam after it hits an object. There is evidence that a dolphin who is listening to the echolocation clicks of another dolphin and to the echoes from those clicks as the bounce off an object will be able to get an ‘image’ of that object. This can all be done just by listening; the ‘eavesdropping’ dolphin will not even need to echolocate themselves. In one experiment conducted by dolphin researchers Dr. Mark Xitco and Dr. Herbert Roitblat, it was found that dolphins could do just that. For their experiment, one dolphin was allowed to echolocate on an object placed behind a visually opaque screen. A second dolphin was then positioned so that he could not echolocate himself, but so that he could still hear the returning echoes from the other dolphin. When the listening dolphin was then asked what object the first dolphin was echolocating on, he had no problem in telling which one it was. Without seeing the object, or even using his own echolocation, the listening dolphin was still getting a mental ‘image’ of the object by listening to the click echoes created by the other dolphin.

When this eavesdropping ability is combined with a dolphin’s ability to determine the direction that another dolphin’s beam is pointing, you have the recipe for an animal that is very sensitive to the relationship between an object and potential directional cues. In the case of the pointing experiments, the dolphins, sensitive to these cues, may have figured out instantaneously that the human point was a cue that could be reliably followed to an object. These ideas still remain to be tested, but whatever the reason; it appears that dolphins are pretty darned good at understanding pointing. For an animal without arms, this certainly is a mystery that requires some kind of explanation.

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