FRIDAY, Feb. 15 (HealthDay News) -- Ever think your dog knows exactly when to misbehave?

You may well be right, according to a neat study out of the United Kingdom.

The recent research showed that dogs seem to understand that humans can't see in the dark -- and they'll take advantage of that fact to sneak a forbidden treat.

For the study, United Kingdom researchers watched 84 dogs under varying light conditions. In each case, the animals were in a room with a person and a tempting piece of food they were verbally commanded not to take. The light conditions changed so that the person was sometimes in the dark and sometimes illuminated. The same lighting changes were done with the food.

Overall, the researchers found, the dogs would try to snatch more food when the treat was obscured in the dark. But the animals did not change their behavior based on whether the person with them was illuminated or in a darkened part of the room.

So the dogs were not acting solely on what they, themselves, could see.

"We believe that this may imply that dogs understand what humans can and cannot see," said lead researcher Juliane Kaminski, of the University of Portsmouth in England.

"The question [of] how they come to such an understanding is a very good one," she added, "and it will definitely be a subject of future research."

According to Kaminski, the findings, published recently in the journal Animal Cognition,add to evidence that "we share some of our cognitive skills with other species."

The traditional view of dogs -- and other animals -- was that they can learn from conditioning (like obeying commands), and that's all. But Kaminski said this study joins other ones in showing that canines can understand their environment, including other beings.

An animal behavior expert not involved in the research agreed. The study showed that dogs seemed to grasp the human perspective of things, said Nicholas Dodman, a professor at Tufts Cummings School of Veterinary Medicine in North Grafton, Mass.

"It shows that the dog, when he believes the owner cannot see him, will become a thief in the night," Dodman added.

And that implies a fairly sophisticated level of thought, he said.

A number of studies have suggested that animals have so-called "primary emotions," like anger or joy. But those are relatively simple on the emotional scale. Whether animals have "secondary emotions" -- more complicated feelings like guilt, jealousy and envy -- is controversial.

Secondary emotions require a level of self-awareness and an awareness of others that some believe are lacking in animals -- with primates like chimps and baboons being the possible exception. But recent studies have been turning up evidence that dogs do demonstrate complicated emotions like jealousy.

"This study give us another piece of evidence," Dodman said. "They do appreciate themselves as entities; they do have thoughts and emotions. And it appears they may have secondary emotions."

Of course, people who live with a dog may need no convincing on that, Dodman noted.

Other humans, however, may well be skeptical. Kaminski said more research is needed to uncover the extent to which dogs understand their environment and the humans in it.

For his part, Dodman said he does not think dogs sit around and ponder existential questions. But they may have deeper thoughts than they have traditionally been given credit for.

"That's uncomfortable for some people," Dodman noted. "We have to admit that animals are much more like us than some people want to believe."

More information

Learn more about canine behavior from the Humane Society.