Barking is a primary form of communication for dogs and as already illustrated, can be extremely useful, yet left unchecked, owners (and their neighbors) can be driven to distraction by a dog who refuses to quiet.
Dogs often bark because they have been reinforced for doing so. Whether the reinforcement has been intentional or inadvertent makes no difference -- behavior that is reinforced tends to be repeated. This maxim is also true of your behavior, your spouse’s behavior and, as most parents know, the behavior of every toddler and teen walking the planet. Puppies sometimes bark in their crates, and in order to stop the noise, owners let them out. Dogs may bark when they’re sitting near the dinner table, and an owner may respond by giving them food. If you’ve been paying attention, you can easily predict the future behavior of these two dogs. This unintentional reinforcement tells the dog that their behavior is effective, and they learn to use it repeatedly to get what they want.