in my e-mail. I posted it elsewhere on DU yesterday. The gist is that dogs have been bred for traits that helped them fit in human societies. This explains why they are more adept at communicating to humans than chimps are. I think it probably works for horses as well.
http://www.the-scientist.com/2004/12/20/18/1/printerfriendly (requires free registration)
DOGS GET THE POINT
Dogs outperform chimpanzees on several tests that require understanding someone else's point of view – what psychologists call "theory of mind" abilities. Here is a simple and compelling test that any dog owner can easily reproduce. Hide a piece of food in one of two opaque containers. The dog is not permitted to see where the food has been hidden but instead must find the food by following a communicative gesture, such as pointing, by the experimenter.
Brian Hare and colleagues at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, found that dogs, even puppies brought up at a kennel with minimal human contact, were fully competent at this task. On the other hand, of nine chimpanzees tested, only two showed any success. Wolves performed above chance, but not as well as the dogs.
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Dogs also appear to understand what people are thinking far more effectively than do chimpanzees. Daniel Povinelli and colleagues at the New Iberia research center in Louisiana gave chimpanzees the choice between begging for food from somebody who could see them, and someone who could not. Surprisingly, chimps showed little understanding that there was no point in begging for food from somebody with a bucket over her head.4 Zsófia Virányi and colleagues replicated this simple test on some Budapest dogs. The dogs were confronted by two unfamiliar women, each holding a liver sandwich. One person faced the dog while the other looked away. Unlike the chimpanzees in Louisiana, Budapest dogs spontaneously begged from only the person who was looking at them.5