its own reward, and with some activities the environment may provide reinforcement such as when the response from dog next door encourages barking. Clicker training Clicker training is a nickname given to a particular type of positive reinforcement training system, based on operant conditioning, that uses a clicker device as a marker and bridge. Clicker training can also be referred to as marker training. The system uses secondary reinforcer (the clicker) as both a marker/signal and a bridge, to let the animal know that s/he performed the desired behavior correctly and therefore a reward is coming, and to avoid inadvertently reinforcing (rewarding) another behavior that may occur after the desired behavior occurs but before the reinforcer is delivered. Primary reinforcers are reinforcers that are required for life, such as food. Secondary reinforcers are things the animal being trained enjoys but that are not required for life, such as toys, praise, etc. The term 'clicker' comes from a small metal cricket adapted from a child's toy that the trainer uses to precisely mark the desired behavior; however, some trainers use a whistle, a word, or even a light as the secondary reinforcer, which becomes "conditioned" once the animal learns that its arrival signals the chance to earn a primary reinforcer. The trainer delivers a primary reinforcer, such as treat, after the noise or signal. A common critique of clicker training is that it is prone to the overjustification effect. Electronic training Electronic training involves the use of an electronic device as an aversive. Common forms are collars which can be triggered remotely at the trainers discretion, or that are triggered by barking, fencing that activates when a dog crosses a buried wire, or mats that can be placed on furniture for example. There are 4 main types of stimulus. Some aids deliver a spray of liquid, typically citronella when triggered. Others emit a siren or vibration or shock of differing intensities. The use of electric shock aversives for training dogs is the subject of considerable controversy. Supporters claim that the use of electronic devices allows training at a distance and the potential to eliminate self-rewarding behavior, and point out that properly used, they have less risk of stress and injury than mechanical devices, such as choke leashes or prong chains. Opponents cite the risks of physical and psychological trauma associated with incorrect or abusive use. In one study laboratory-bred Beagles were