Clicker training is the process of training an animal using a conitioned reinforcer, which indicates to the animal ("marks") the precise behavior that was correct. It was originally discovered and used with laboratory rats and pigeons, and later was used in training animals such as dolphins and pigeons. It is a technology derived from the study of operant conditioning in behavior analysis. The name "clicker training" is used because the primary tool is a small mechanical noisemaker called a clicker. Clicker training has also been successfully used in the training of a huge variety of species including many marine animals, livestock, household companion animals, equines, etc. It is used in the training of service animals, police K-9's, search and rescue animals, animals used in military activities, and many more. Even common house cats are easily trained using clickers and treats.