(CNN) Whether you call them gray hairs or stress highlights, world-renowned animal scientist and autism advocate Temple Grandin wants you to know that dogs may get them prematurely, too -- possibly when stressed, such as being left at home alone.

Premature graying in dogs may be an indicator of anxiety and impulsivity, according to a study published in this month's edition of the journal Applied Animal Behaviour Science , in which Grandin served as a co-author.

Camille King, an animal behaviorist and owner of the Canine Education Center in Denver, noticed a few years ago that many impulsive and anxious dogs seemed to be prematurely turning gray. When King told Grandin about her observations, Grandin said she encouraged King to lead the research.

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"The first thing I thought of when she told me that were the presidents, and how they age and get prematurely gray," said Grandin, professor of animal science at Colorado State University, referring to American commanders in chief

"The fact that presidents turn prematurely gray was one of the things that made me encourage her to do the study," Grandin said. "Basically, (the study findings) validated what she had seen in years of doing dog behavior work."

'I was surprised'

The study, conducted at Northern Illinois University , involved 400 dogs, 4 years old or younger, with non-white-colored hair so the researchers could adequately determine degrees of graying.

"Normally, dogs wouldn't be gray at age 4," Grandin said.

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The researchers took two photos of each dog and asked each dog's owner to complete a 21-question survey, which included questions about the dog's anxious or impulsive behaviors. Both behaviors hold clues to how stressed the dog might be, sort of like how emotional instability and anxiety are associated with stress in humans.

Anxious behaviors include whether the dog whines or barks when left home alone or cringes or cowers in groups of people, and impulsivity can be seen in whether the dog jumps on people when greeting them or excessively tugs on the leash when going on walks.

The dog owners were unaware of the true purpose of the study when they completed the questionnaires.

Next, the researchers compared the survey responses with how much gray hair appeared on the dogs' muzzles in their photos.

Grandin helped the researchers build a scoring system to measure the degrees of grayness: A score of 0 is "no gray;" 1 is for gray on the front of the nose only; 2 is for gray hair halfway up the muzzle; and 3 is "full gray."

It turned out that a high grayness score was significantly and positively predicted by survey responses that indicated both high anxiety and impulsivity.

"Essentially, the results indicate that for each standard deviation increase in the measured trait, either anxiety or impulsiveness, the odds of being in a higher rating category of muzzle grayness increase 40% to 65%," said Thomas Smith, a professor at Northern Illinois University's Department of Educational Technology, Research and Assessment, who was a co-author of the study.

Smith added that he was initially skeptical that a dog's premature muzzle grayness might be linked to anxiety and impulsiveness.

"However, when we analyzed the data, the results actually were striking," he said. "I was surprised."

A similar association between stress and premature graying possibly could be found in other mammals, outside of humans and dogs, but more research is needed, Grandin said.

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The new study appears to extend what has been previously seen in people -- the relationship between stress and gray hair -- to dogs, said Matt Kaeberlein, a professor and co-director of the University of Washington's Dog Aging Project, who was not involved in the new study.

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"There are a few things about this study that I really like. One is that it nicely illustrates another way in which dogs and humans are similar, specifically in this case, the way we interact with our environment to experience stress. I like the innovative approach of applying facial image recognition to dogs," Kaeberlein said.

"I do think it's important to keep in mind that while hair graying is a useful 'biomarker' of aging and experienced stress, it is not particularly precise. We should avoid interpreting causation from correlation," he said about the study. "Many dogs and people get gray hair for reasons unrelated to their perception of stress or anxiety, so while anxiety (or) stress appears to cause hair graying, gray hair is not necessarily caused by anxiety or stress. In other words, just because your dog gets gray hair doesn't mean she or he is stressed out."

For instance, more research is needed to determine how much genetics might play a role not only in premature graying in young dogs but also how a dog might respond to stress, Grandin said. She added that additional research could also determine how much of the study results were influenced by anxiety and impulsivity, respectively.

"There's probably some genetic influence where some dogs that are impulsive and anxious don't turn gray. You see, that would be your genetic interaction, but when you take a big population of dogs, it statistically comes out that anxious and impulsive dogs are more likely to start turning gray before age 4," Grandin said.

"Genetic factors are important, but genetic factors also can be modified by experience, so you can't just say an animal's hard-wired genetics, it's not. It's both. Both genetics and the environment are important," she said.

What to do if your dog is stressed

If pet owners notice that their dog is prematurely graying, they should make an appointment with their veterinarian or an applied animal behaviorist, said King, the lead author of the study.

"A medical workup could be completed along with a screening for anxiety or stress," King said.

"Once a dog is screened, and if found to be anxious or impulsive, there are many treatment options, such as behavior modification programming, medication, alternative techniques such as a pressure wrap," she said. "It is very important to have the dog professionally examined to get to the root of the problem, and not assume that because the dog is prematurely gray, it is related to stress."

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If the dog is stressed, what might be a common cause? Being left home alone, Grandin said.

"I've been very concerned about all these dogs spending so much time home alone all day. I walk through the streets where I live at 3 o'clock in the afternoon and I can hear dogs barking and whining in houses," Grandin said.

"We have bred dogs to be social beings, and then you leave them home all day and they don't get to do much socializing," she said. "I think the home alone problem is a big factor. This is just my opinion."

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Grandin said one of her colleagues tends to leave his dogs with a friend when he is away from home, and she encourages others to do the same.

"Some people take their dogs to doggy day care. Some of those are good. Some of them are run poorly," she said. "If you have a dog that does not handle being home alone well, maybe you need to be making arrangements to drop him off at the next door neighbor's on your way to work."