If your dog destroys the furniture when you are away, it could be a pessimist, researchers have concluded.

A study has found that some dogs are natural gloom-mongers while others have sunnier dispositions.

"We know that people's emotional states affect their judgments and that happy people are more likely to judge an ambiguous situation positively," said professor Mike Mendl, an author of the study and head of animal welfare and behavior at Bristol University.

"What our study has shown is that this applies similarly to dogs."

To measure canine psychology, researchers trained dogs to recognize that bowls on one side of a room contained food, while bowls on the other side were empty. They then placed the bowls in "neutral" locations between the two sides.

Just as happy people tend to see the positive in any situation, so optimistic dogs sprinted toward the bowl, expecting to find food, while pessimistic dogs hesitated or ran more slowly.

The study, published in Current Biology, which looked at 24 dogs at two UK animal centers, found that dogs' temperaments correlated with their behavior when separated from their owners.

Dogs that saw the bowl as half-full were calmer when left alone, sure their owners would return, while pessimistic dogs were more likely to worry, bark and misbehave.

About half of the 10 million dogs in the United Kingdom show "separation-related behavior" at some point, Mendl said.

Instead of getting rid of anxious dogs or ignoring them, owners should recognize that their dogs may have emotional issues and seek treatment for them, he said.