Some see the bowl as half-empty; for other dogs, it's half-full.
At least that's what researchers at The University of Sydney in Australia say. Their new study shows that some dogs are inherently more optimistic than others.
"This research is exciting because it measures positive and negative emotional states in dogs objectively and non-invasively," study leader Dr. Melissa J. Starling, an animal behaviorist at the university, said in a written statement. "It offers researchers and dog owners an insight into the outlook of dogs and how that changes."
For their study, the researchers trained dogs to respond to two different tones, each an octave apart. One tone accompanied a reward of a half-bowl of lactose-free milk, while the second tone resulted in a less-alluring half bowl of water. Once the dogs learned to associate each tone with its reward, the researchers had the dogs listen to "ambiguous cues" -- tones that were unfamiliar to the animals -- and studied their responses.
What did the researchers find?
Some dogs reacted positively to the unfamiliar sounds, indicating that they expected a treat of milk might follow. The "pessimists" of the group, meanwhile, failed to react at all. The researchers concluded that a dog with an optimistic personality expects more good things to happen, and is thus more likely to take risks with the expectation that doing so can lead to rewards. Meanwhile, the researchers described pessimistic dogs as being generally "more cautious and risk averse," and therefore more content with the status quo and less eager to try new things.
"Pessimistic dogs appeared to be much more stressed by failing a task than optimistic dogs," Dr. Starling said in the statement."They would whine and pace and avoid repeating the task while the optimistic dogs would appear unfazed and continue."
But the researchers cautioned that neither doggy disposition was necessarily better than the other. Instead, trainers may be able to take advantage of the dogs' different personalities to find the best role for them as service dogs.
And that's a good thing: No one wants a guide dog that's overoptimistic about its ability to cross a street in time.
"If we knew how optimistic or pessimistic the best candidates for a working role are, we could test dogs' optimism early and identify good candidates for training for that role," Starling said in the statement. "A pessimistic dog that avoids risks would be better as a guide dog while an optimistic, persistent dog would be more suited to detecting drugs or explosives."
The research doesn't have any immediate implications for pets at home, though it could help reshape how we assess animal welfare, says Starling.
The "Canine Sense and Sensibility" study was published in the Sept. 17 issue of the journal PLOS ONE.