The dog bark is essentially an alarm call. They see or hear something and they want to pass that on to the other members of the pack including the human members. Therefore, it is likely that your dog is not barking at nothing but that there is something out there which you have not noticed. This, in turn, is because their senses are sharper than those of humans.
An alternative reason is that your dog has become bored. They bark for “fun”. They might be joining in with a bark that they have heard somewhere else. It is a way of releasing energy.
Someone asked why their dog was barking at the wall! Once again, it appears that your dog has heard something either inside the wall or on the other side of it and he or she is barking a warning. An alternative reason for barking at a wall might be that the dog has a medical problem.
There are alternatives to the reasons I’ve stated. This is because there are alternative reasons for barking such as: territorial barking, alarm barking (this is the one which I have referred to as being the original reason), attention-seeking barking, greeting barking, socially facilitated barking, frustration-induced barking (I have mentioned this above), illness or injury barking and separation-anxiety barking.
I guess you’ll have to put on your detective hat and work out which one applies. They’ll be a reason and that reason will be connected to a human and human behaviour.
Some dogs bark excessively. The reasons listed above and combined would result in a dog barking excessively. There may also be an issue with the early years of the dog’s life and how the dog was raised. John Fisher in his book Think Dog immediately discusses how a dog’s mind develops. He is primarily concerned about the underlying causes of a dog’s behaviour rather than simply treating symptoms.
He says that he frequently sees dogs with behavioural problems, the underlying cause of which is “ignorance on the part of the breeder”. He refers, for example, to a condition called kennelosis also known as kennel syndrome in which dogs are kept in kennels up to and over the age of 14 weeks. They don’t make good pets. They can’t handle stressful situations and cannot identify with people.
There is also a failure sometimes of human socialisation. These dogs are over socialised with other dogs but under socialised with people.
Dogs bred on puppy farms are often taken from their mothers before weaning and much too soon and in some cases at four or five weeks old. These dogs sometimes have never learned how to be a dog and have missed out on the period of canine socialisation. They often become aggressive and are difficult to train. This is because the mother was not around to discipline them during their formative weeks. The Canine Socialisation Period and the Human Socialisation Period are vitally important in respect of how a dog’s temperament is developed and is evident when an adult.
Fisher writes that not enough emphasis is given to environmental factors such as referred to above and how they have a bearing on a dog’s temperament compared to those which are inherited. A dog with temperament problems may, as I understand it, bark too much because of perhaps anxiety and fear. Long-term behaviour problems in dogs and indeed in cats can often be put down to the early weeks of socialisation.