Over our long shared history, dogs have developed a range of skills for bonding with human beings. Their ability to make sense of human instructions like "lay down" is just one such skill. But whether dogs understand human intentions, or merely respond to outcomes, remains unclear. The ability to recognize others' intentions is a basic part of Theory of Mind, long regarded as uniquely human. Can dogs also distinguish between something done on purpose and something done by accident?
To answer this question, a team of researchers in Germany conducted an experiment that examined how dogs reacted when food rewards were held back. They found that dogs responded differently depending on whether the actions of the experimenter were intentional or unintentional.
The experiment was conducted under three conditions. In each condition, the dog was separated from the human tester by a transparent (透明的) barrier. Then the experimenter fed the dog pieces of dog food through a gap in the barrier. In the "unwilling" condition, the experimenter suddenly withdrew the reward through the gap in the barrier. In the "unable-clumsy" condition, the experimenter brought the reward to the gap in the barrier and "tried" to pass it through the gap but then "accidentally" dropped it. In the "unable-blocked" condition, the experimenter again tried to give the dog a reward, but was unable to because the gap in the barrier was blocked. In all conditions, the reward remained on the tester's side of the barrier.
Not only did the dogs wait longer in the unwilling condition than in the unable conditions, they were also more likely to sit or lie down-actions often interpreted as being uninterested-and stop wagging their tails.
The team acknowledges that their findings may be met with challenges and that further study is needed to deal with alternative explanations, such as behavioral cues (暗示) on the part of experimenters or knowledge transfer from earlier dog training. "Nevertheless," the paper concludes, "the findings present important initial evidence that dogs may have at least one aspect of Theory of Mind: the capacity to recognize intention-in-action."
