If your dog looks pleased to see you – it is probably because it loves the particular way you smell.

如果你的狗一见到你就显得很开心的话，有可能是因为它喜欢你散发出的独特气味。

The odour of a familiar human apparently lingers like perfume in the animal's brain – where it triggers an instinctive emotional response, research published yesterday reveals.

Our scent acts on a part of the canine brain associated with reward and the strongest reactions are produced by humans that pets know best, say scientists in America.

Gregory Berns, of Emory University in Atlanta, said: ‘While we might expect that dogs should be highly tuned to the smell of other dogs, it seems that the "reward response" is reserved for their humans.

'When humans smell the perfume or cologne（古龙香水） of someone they love, they may have an immediate, emotional reaction that's not necessarily cognitive.

'Our experiment may be showing the same process in dogs. But since dogs are so much more olfactory than humans, their responses would likely be even more powerful than the ones we might have.

'It's one thing when you come home and your dog sees you and jumps on you and licks you and knows that good things are about to happen.

'In our experiment, however, the scent donors were not physically present.

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'That means the canine brain responses were being triggered by something distant in space and time. It shows that dogs' brains have these mental representations of us that persist when we're not there.'