There's a reason why we bond with some dogs more than others

If you've ever wondered why some dogs seem eager to make eye contact with people and others don't, a new study offers some clues. Dogs that are snub-nosed, young or playful, and those that have been bred to respond to visual cues, such as shepherd breeds, are the most likely to look directly into the human eye, researchers have found.

And it's that loving eye contact with a dog that can help build a close bond with humans.

"Eye contact is a very important signal for us humans," said the study's lead author, Zsófia Bognár, a Ph.D. student in the department of ethology and a research member of the Senior Family Dog Project at Eötvös Loránd University in Hungary. "It can enhance communication, cooperation and the relationship between dog and owner." The study was published Thursday in the Nature journal Scientific Reports.

While some dogs might naturally seek eye contact, that doesn't mean others can't learn, Bognár said in an email. "Although dog-human eye contact can be affected by at least four independent traits on the dogs' side, it does not mean that these are the only things which determine your relationship with your dog."

Other studies have shown that humans and dogs benefit from locking eyes: Levels of oxytocin, the bonding hormone, rise for both species when they make and hold eye contact.

To explore what factors might make eye contact more likely, Bognár and her colleagues rounded up 125 family dogs for the behavior experiment. All the dogs were run through a battery of tests, which started with the dogs' meeting an unfamiliar experimenter. In a later part of the series, the dogs were invited to play with the experimenter.

The 10th test evaluated the dogs' willingness to make eye contact with their new human friends.

A person stood in the middle of a room in the lab with a food pouch attached to her belt, called the dog to her and threw a piece of sausage on the ground when the dog arrived. The experimenter then stood still and waited until the dog made eye contact with her and then rewarded the dog with another bit of sausage.

The researchers counted up how many times each dog made eye contact within five minutes.

Shorter-headed dogs, such as boxers, bulldogs, French bulldogs, Boston terriers and pugs, have that earnest gaze because their eyes are structured differently from those of other dogs; they have more retinal ganglion cells, which are responsible for initial processing visual information in the center of their visual fields, the researchers said. That means they can more easily focus on what's in front of them, such as human owners.

Dogs with long snouts have eyes more geared to peripheral vision; that is, seeing what is beside them, rather than what is in front of them, Bognár said.

Puppies and playful canines were also most likely to stare into their owners' eyes. The working or herding dogs are a natural, because they are bred to "perform their tasks alongside humans," Bognár said. "They are in continuous visual contact with their owner or handler."

Pet dogs that don't naturally seek eye contact can be trained to do it.

"You can improve your dog's willingness to form eye contact, which could improve your relationship, too," she said.

Dr. Katherine Houpt, an emeritus professor of animal behavior medicine at Cornell University College of Veterinary Medicine, in Ithaca, New York, said it's a good idea to train a dog to make eye contact.

"Because if you say 'look' and the dog looks into your eyes, he's not focused on the car going by or another dog he wants to chase," Houpt said. "You'll have more control over him, as well as a better relationship."

Related: To dogs, the sight of another dog is much more exciting than the sight of a human.

"It's really easy to train a dog to do it," Houpt said. "You hold a piece of food away from you. Most, if they can't get what they want, will look up at you. As soon as they do, you say 'look' and give the food. After about 20 times, it becomes a command."

Eye contact is important to humans, said Anne Burrows, a specialist in evolutionary anatomy and a professor at Duquesne University in Pittsburgh.

"I volunteer at a dog shelter, and those that do not make eye contact don't go very fast," she said.