A clicker, sometimes called a cricket, is any device that makes a clicking sound, usually when deliberately activated by its user.
They usually consist of a piece of thin metal or plastic held in a casing so that the metal is slightly torqued; depressing one end of the metal causes it to pop out of alignment and releasing it causes it to pop back into alignment, each time making a sharp click.
With some clickers, the user depresses the metal directly with thumb or finger; with others, a button extends above the surface of the casing so that depressing the button makes the metal click.
Clickers were first used by marine mammal trainer Karen Pryor as a way of communicating with their animals. Dolphins and whales communicate underwater through a series of clicks and whistles known as echolocation, and the clicker allowed a trainer to produce signals they were more likely to understand.
Nowadays, clickers are used to train all kinds of animals, most commonly dogs. When associated with a treat, a click allows the owner to mark the precise moment the desired behavior is executed.