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If your dog gets upset when you walk out of the door, it's probably a pessimist.

If your dog gets upset when you walk out of the door, it’s probably a pessimist.

Scientists have shown that for every dog who believes its water bowl is half full, another is convinced the bowl is half empty.

Those who are naturally optimistic are sure their owners will return, while the pessimists assume they have been abandoned.

While the discovery that dogs have all-too-human personalities won’t surprise owners, the researchers say it sheds light on why some animals are happy to be left, while others suffer separation anxiety.

Professor Mike Mendl, of the animal welfare and behaviour research group at Bristol University who led the study, said: “We can use findings from human psychology research to develop ways of measuring animal emotion. We know happy people are more likely to judge an ambiguous situation positively.

“Our study shows that this applies similarly to dogs - that a ‘glass-half-full’ dog is less likely to be anxious when left alone than one with a more ‘pessimistic’ nature.”

The team studied 24 dogs at two animal shelters. Each was first assessed to see whether it suffered separation anxiety - behaviour such as barking or scratching at the door when left alone.

Each dog was then trained to expect that when a bowl was placed at one location in a room it would contain food, but when it was put in another it would be empty. Once the dogs had learned that only some bowls contained a meal, the researchers placed bowls in “neutral” locations in the room.

Dogs that bounded up to the bowls expecting food were classified as optimists. But those who didn’t bother were deemed pessimists. Animals who suffered separation anxiety were far more likely to be pessimists, the researchers say in the journal Current Biology.

“Around half of dogs in the UK may at some point perform separation-related behaviours - toileting, barking and destroying objects around the home,” said Professor Mendl.

“Our study suggests that dogs showing these types of behaviour also appear to make more pessimistic judgments generally.” - Daily Mail