Nov. 6, 2013 -- Boomer the dog has a bone to pick with the world. He wants to be accepted for his doggie lifestyle.

Born Gary Matthews, the retired technology worker and a self-confessed "nerd" thinks he is a dog. The 48-year-old wears a dog collar, eats dog food from a bowl — his favorite is Pedigree – and loves milk bones and dog cookies.

"I don't eat dog food every day," Matthews told ABCNews.com "It's a special thing for me to do once in awhile to get closer to feeling like a canine. I eat the canned kind. It's not bad -- it tastes OK. I eat regular human food, too, like pizza."

But he has the most fun wearing his dog suit, code-named "Papey," because he made it from shredded paper. He wanders around the streets of his hometown Pittsburgh, barking at cars and digging holes in the backyard.

"When I go out, I get the feeling and I wave to people as a dog," he said. "I go to local festivals because kids like the costume. That's my way of reaching out to people and spreading the word that I can be myself in life. They see that you can have fun in adulthood. But I am kind of a loner dog."

"Sometimes I sleep in my dog house, which is up in the attic -- I built it myself," said Matthews. "It's made out of wood and I can take it apart and move it. I go up there and read a book. It has a little night light and is like a club house."

The mild-mannered and seemingly rational man even has a telephone answering machine that barks. His emails say "pawed" instead of, "said." and he runs a website Boomer the Dog, and a podcast.

Listen to Boomer's bark.

Matthews said he got the name from the television series "Here's Boomer," which ran from 1979 to 1982 about a stray dog.

But his obsession started long before that, with a dog named Pongo from Disney's "101 Dalmatians" and a series of Disney movies that began in 1959 called "The Shaggy Dog."

"Sometimes, I would bark or maybe get into a big box and peek out with my paws over the side of it like a dog would do." -- Gary Matthews

"It's been a long process," he said. "It started when I saw "The Shaggy DA" in 1976 when I was 11 years old. I went with my Dad to see it. I was already a dog freak and collecting pictures of dogs. I saw this movie and there was something different about it -- the dad transforms into a big sheep dog. I had never seen that idea played out anywhere."

Grown-up man wears diapers, sleeps in crib.

"I started playing dog and getting into it," said Matthews. "It was like a kid thing. Sometimes, I would bark or maybe get into a big box and peek out with my paws over the side of it like a dog would do. In a couple of years, I really got into it. ... Maybe I was looking for a personality to have."

He would draw dogs and watch every TV show about dogs. His father, a pharmacist, became less supportive of Matthew's growing canine identity and worried about his future.

As Matthews grew older and was "getting out in the world," he said he was drawn to the furry white television mutt, Boomer – a "nerd type of dog" -- and took his name.

Matthews was featured in a June National Geographic special, "Extreme Anthromorphism: Boomer the Dog."

The word anthropomorphism comes from the Greek words "anthros" for human and "morph" for form and refers to the attributing human qualities and emotions to nonhumans.

Matthews said he has never been in trouble with the law and is not seeing a psychiatrist or taking any kind of medications for mental illness. Money is not a problem. When his parents died, he inherited their house and they left him a trust fund to live on.

"My only direct relative is a half-sister who lives in California," he said. "She is opposed to me being a dog and hates the concept. She seems to think I am crazy."

Not all people think he is nuts. Lois Achchammer of Winterville, Ohio, has known Matthews for years as "Boomer." He was a friend of her son, Mike, and they built short-wave radios together.

"He's a real nice guy," said the 68-year-old retiree. "When I first met him I didn't know it was because he was a dog, I thought it was a nickname."

"He's very quiet, very reserved and very polite and well-mannered," said Achhammer. "I couldn't say anything bad about him. They say there is a fine line between insanity and genius and I think he's on that line. He's a very intelligent young man."

Matthews is so dogged about having his name changed to Boomer that in 2010, he petitioned the court, but was denied. Today, he hopes to try again and tells his story to prove to the judge that he is not doing it for fraudulent reasons.

"Going public with being a dog isn't just about the name change," said Matthews. "That's only the most recent thing that I'm focusing on, because really, being a dog is about everything -- it's the way that I live."

Matthews said he has no idea why he is so drawn to being a dog and admits it was hard being different as he was growing up. "I got flak for it," he said. "My parents didn't like it. Earlier on, they saw it as a kid thing and they laughed. But at a certain point in time there are adult expectations and they want you to go off to work and date. Society wants to straighten you out."

In school, the other children teased Matthews and when he was still acting like a dog in high school he was sent to a "special school" for teens who have social and emotional problems.

Matthew has never dated and has no interest in marriage or children. "I have good friends and I substitute friendship for anything closer than that," he said.

He also belongs to a group called "furries" – people who dress like animals and meet at clubs around the world. "I have a group of fans, people who perform as mascots – they are a nerdy group like trekkies and like dog play," he said.

Julia Ramos-Grenier, who practices forensic neuropsychology in Tucson, Ariz., and has not treated Matthews, said she had some concern over what may be a compulsion to behave as a dog.

"This is an unusual kind of thing and there isn't really a lot of research to give you some idea what is going on psychologically in the mind and the brain," she said. "The one thing I worry about is it sounds like he is alone and therefore that starts to affect his personal life."

In compulsive behavior, a person "needs to do it and feels better when they do it," said Ramos-Grenier. "It releases tension or anxiety and is something positive for them. The behavior starts to be a problem when it goes over the line."

Like Matthews, she said she has no idea why he developed this compulsion to be a dog.

"Maybe it was his natural make-up when he was developing his personality or it could have been a traumatic event or an association with something pleasurable," she said. "Maybe he got a lot of reinforcement and a loving kind response from dogs that he didn't get from other people."

But Matthews insists there is nothing wrong with him: "I see it as a lifestyle. I just live differently."

And he was thrilled to be the subject of an interview by ABCNews.com, writing to this reporter, "Woof, woof! Good barking with you today."