So what is the purpose for the clicker? How well does it work?
Clicker training is fun for both owner and dog and is based on classical conditioning, one of two main components in scientific learning. The other being operant conditioning. It is how we all learn. Operant conditioning simply means you do this and this happens. There is a consequence for every behavior. For a wanted response, there is a primary reinforcer, the reward. Classical conditioning makes use of a secondary reinforcer....the clicker. You do this......(a desireable behavior) and you hear the click to mark that behavior and get a treat following. (primary reinforcer) All behavior must be reinforced in order to increase the probability of its recurrence. Reinforcement is what drives behavior.
Clicker training or its concepts is what is being used widely today all over the world with modern trainers on account of a lot of scientific advancement and a lot of studies. It is used in many, many venues of dog training. (along with other mammals) Its used in movie actor dog training, service dog training, S&R, dog sports, obedience, rehabilitation of behavior problems including but not limited to severe aggression problems. Its wonderful for that because so many aggressive behaviors are fear based as well as brain chemistry being a culprit, improper cortisol response etc. It is counterproductive to punish aggressive behavior and this has been used with extreme success in that arena. A lot of aggressive displays don't always look like they're fear based, but they are and aversives only exasperate the problem, supress it and the underlying catalyst is still there.
Anyhow, clicker training also teaches a dog better HOW to learn better than forced or compulsive methods or with the use of a lot of aversives. I think it makes for a more thinking dog. And I like my dogs to be participants in their training, not marienettes. Force, choke collar yanking, too much physical manipulation of the dog does not give a dog a choice. Choice is a thinking process.
Anyhow Cindr, if you're intested, may I recommend a few books? *Culture Clash by Jean Donaldson, Don't Shoot the Dog by Karen Pryor, The Power of Positive Training by Pat Miller. These are excellent books which highlight what is best for the dog, their behavior, our understanding of their behavior and how they learn.... and well worth the money spent.