Clicker is used to link a behaviour with the real reinforcement

In order for consequences to have an impact on a behavior, they have to be immediate; otherwise, it is impossible to associate those consequences with that particular behavior. The ability to speak allows people may to explain event distant consequenes behaviors. However, in case of animals the only option to mark a behavior is to use reinforcement or punishment.

In case of simple, not quick behaviors, it is possible to reinforce during the activity (e.g., a sitting dog, a bowing horse). However, many behaviors cannot be reinforced immediately(i.e., in middle of doing), because it is impossible to do so. Those behaviors may be either too quick (e.g., pecking a target), or they may be simply impossible to reinforce (e.g., a jumping horse).

Such problems may be solved with use of a marker. Marker is a neutral stimulus, which we are able to elicit at any moment (a whistle, a click, a flash of light), and that was previously associated with a reinforcement. With use of a marker we are able to provide a precise information to an regarding which behavior is being reinforced. Moreover, we are creating a bridge between a behavior and a real reinforcement (that may be provided a little bit later),

It is not important what kind of a marker we are using, optical, sound, or touch marker. Surely, some markers will be better than the others in certain situations (e.g., a clicker for a deaf dog or a fish makes no sense at all). Use of a sound marker (a clicker, a whistle) is much more convenient due to the fact that the eye conctact with the trained animal is not needed. A clicker is the most frequently used marker, mainly because of its simple construction and comfortable use. Clickers may vary from the simplest ‘boxes with a thin piece of metal’ to electronic devices which are able to produce various kinds of sounds.

Theoretically, even a word such as: ‘Good!’ may become a marker. However, research show that such markers are far from perfect. They are not as precise as clicker (Try to say ‘Good!’ excaly when chicken’s peck hits the table). In order for marker to become a conditional stimulus (such stimulus is not processed by cerebral cortext so it is quicker) it has to be always indentical and neutral. Unfortunately, human speech is neither neutral – we use it by definition to convey messages, nor identical – it is always interpeted by cerebral cortex. Of course, such marker will work; nonetheless, the achieved results will be significantly worse.