CHICAGO (CBS) –  Ever wonder what your dog would do if someone broke in your home? Would your animal attack, or is your pet all bark and no bite?

To find out, CBS 2 put four dogs to the test and asked police K-9 trainer Gary Tippett to pose as an intruder in “full bite” protective gear. Several cameras inside the homes captured the dogs’ reaction.

Reporter Chris Martinez reports on the results.

First up: Ollie, a 12-year-old Shetland Sheepdog. Ollie’s owners admit the dog doesn’t warm up to strangers easily and expected the dog would be anything but inviting to the intruder.

“He’s going to try to keep them from going further into the house,” owner Beth Corso predicted.

Ollie certainly looked ferocious at first, but backed off once Tippett was inside the house. The dog kept a safe distance from the stranger, offering an occasional bark or growl.

Next up: Wrigley, a 2 ½-year-old yellow Labrador retriever. His owners said the dog has a reputation for having a deep, intimidating bark.

Wrigley unleashed that big bark as the intruder approached. But once Tippett got one foot in the door, the dog followed commands and even followed the stranger through the house.

“The guy started talking to him and petting him,” owner Wendy Merkel says.

So what about breeds with a tougher reputation? The owner of REO, a 14-month-old German Shepherd, was convinced the dog would protect his home.

“I expect a lot of barking at first, and then as soon as he actually comes in, she’s probably going to go in and grab his arm,” Stephen Bledsoe says.

REO delivered on the barking as Tippett approached the house, but then made nice with the intruder and even let him leash her up and walk her out the front door.

“To see him walk her out with a leash was definitely, definitely interesting,” Bledsoe says, smiling.

Cameras captured a similar reaction from Cuneo. The owners of the 7-year-old, 100-pound Rottweiler expected the dog would try to keep the intruder from entering.

“I’m hoping he barks and keeps the person out,” owner Gina Sorrentino says.

Cuneo barked as Tippett approached the house, but only twice.  The dog then took treats from the intruder and even followed commands.

“What’s even more surprising is when he told him to get in his kennel and he went and sat in the kennel, and didn’t come out until he told him to come out,” Sorrentino says.

So why did none of the animals attack?

CBS 2’s expert says unless a dog is trained to engage an intruder, there’s little chance it ever will. Tippett says owners should instead condition their dog to bark when intruders or strangers are near.  He believes when it really counts, a good bark is all you need.

“They’ll go somewhere else, and that’s what you want them to do,” Tippett says.