It’s pretty typical to just accept guilt as something we feel as humans, but it’s actually a very complex emotion. It’s a something children don’t develop until between 3-6 years of age, and they tend to have a pretty wobbly grasp of the concept until closer to 5 or 6. Many dog owners will swear that their dogs “look guilty” and therefore know when they’ve done something wrong while their owner was absent, but when guilt in dogs is studied, the conclusion seems to be that we’re giving dogs too much credit. In this case, that extra credit is actually pretty harmful to them. If their owners believe they know what they’ve done wrong and they’re clueless, that very seriously impacts training and sets dogs and owners up for failure.
First, lets take a look at guilt. This is how Merriam-Webster defines “guilt”:
feelings of culpability especially for imagined offenses or from a sense of inadequacy : morbid self-reproach often manifest in marked preoccupation with the moral correctness of one’s behavior <aggressive responses originating in inner guilt and uncertainty>
Almost any definition will imply that a person feeling guilt has a moral code and that it’s been broken. It’s also a secondary emotion, meaning that it’s an emotion we feel in response to other more basic emotions, such as fear, and depends on being able to remember and mentally recreate a past deed or event and its context and ramifications. Guilt seems to take more cognitive ability for soul-searching than most people would credit their dogs with if they really think about it, but the myth of doggy guilt is pervasive.
Anecdotally, many people involved in professional dog training have lots of stories that support that dogs don’t quite “get” why their owners are angry when they’ve done something wrong while they were gone. A great example given in Decoding Your Dog, a book written collectively by American College of Veterinary Behavior members, is a dog who was brought in for a behavioral evaluation because his owners were unable to house train him. He would hide and cower when his owners came home and find he had pooped in the house. Because he hid before they found the poop, they assumed he knew he was doing something wrong. What he actually seems to have learned is that if both he and poop are present when his owners get home, he’ll be punished. This is really brought home when his owners later get a puppy, and their older dog hides and cowers when the puppy poops in the house, even though the poop is much too small for it to be his. Dogs don’t seem to be able to connect their past misdeeds, such as actually pooping in the house, with the punishment. They’re astute observers of human body language and behavior, so they will connect things such as a disordered room or poor and pee when their owners come home with anger or punishment, but they’re not able to make the leap to understanding that you’re angry because they made the mess.
A study from The Dog Cognition Lab testing whether dogs display guilt is described in detail in Dog Sense, a book by Dr. John Bradshaw. The study finds that the behaviors most owners associate with “looking guilty” are more accurately appeasement behaviors and displays for fearfulness. The dogs in the study were taught not to take a food treat when their owners instructed them not to. A treat was placed on a table and their owners instructed their dogs not to eat it, and then left the room. After their owners left the researchers either encouraged the dogs to eat the treat or removed them so the dog was unable to eat the treat. Before their owners returned they were randomly told that their dogs had or had not disobeyed, and their behavior when greeting their owners was evaluated. Dogs “looked guilty” when their owners believed they were guilty, and dogs which were most often punished for things they had done while their owners were gone were the most likely to show behaviors indicating “guilt.” These dogs have figured out that fearful and appeasing behaviors actually result in less scolding or anger, so they continue to display these body postures, but that doesn’t actually mean that they know what they’ve done.
Even if you’ve never punished your dog for something they’ve done while you were gone, you may get some seemingly “guilty” looks if your dog can find a pattern where you’re consistently angry about something when you come home. Dogs have evolved to pay serious attention to human body language, and that focus allows them to read your feelings pretty accurately, even if you think you’re keeping your anger to yourself. In the case of dogs that have been rehomed, they may also have expectations of punishment from their last home. Your dog’s “guilty looks” are a plea for you to please be happy with them, not an admission that they know exactly what they’ve done wrong.
As humans we want to be able to go back and fix things that happened in the past, but that’s just not how dogs learn. If you come home to find your dog has made a horrible mess, that’s already done, and there’s no training or learning to be gained from it, except for on the human side of the equation. Try to set your dog up for success if he has accidents while you’re gone. Keep him in a relatively dog-proof area with a baby gate or exercise pen, with toys and food puzzles to entertain him. Have reasonable expectations for how well your dog tolerates being alone and how long he can go without a bathroom break or something to do. Treat potential separation anxiety immediately before it has a chance to become worse, and consult your vet for antianxiety medications to help with training if necessary. The only scientifically sound way to prevent misbehavior while you’re gone is to prevent it before it happens.