A token economy is a system of contingency management based on the systematic reinforcement of target behavior. The reinforcers are symbols or tokens that can be exchanged for other reinforcers. A token economy is based on the principles of operant conditioning and behavioral economics and can be situated within applied behavior analysis. In applied settings token economies are used with children and adults; however, they have been successfully modeled with pigeons in lab settings. Basic requirements Three requirements are basic for a token economy: tokens, back-up reinforcers, and specified target behaviours. Tokens Tokens must be used as reinforcers to be effective. A token is an object or symbol that can be exchanged for material reinforcers, services, or privileges (back-up reinforcers). In applied settings, a wide range of tokens have been used: coins, checkmarks, images of small suns or stars, points on a counter, and checkmarks on a poster. These symbols and objects are comparably worthless outside of the patient-clinician or teacher-student relationship, but their value lies in the fact that they can be exchanged for other things. Technically speaking, tokens are not primary reinforcers, but secondary or learned reinforcers. Much research has been conducted on token reinforcement, including animal studies. Back-up reinforcers Tokens have no intrinsic value, but can be exchanged for other valued reinforcing events: back-up reinforcers, which act as rewards. Most token economies offer a choice of differing back-up reinforcers that can be virtually anything. Some possible reinforcers might be: Material reinforcers: candy, cigarettes, journals, money Services: breakfast in bed, room cleaned, enjoyable activities Privileges and other extras: passes for leaving a building or area, permission to stay in bed, phone calls, having one's name or picture on a wall. Back-up reinforcers are chosen in function of the individual or group for which the token economy is set up, or depending upon the possibilities available to the staff. Prior to starting the staff decides how many tokens have to be paid for each back-up reinforcer. Often, price lists are exposed or given to the clients. Some back-up reinforcers can be bought anytime, for other exchange times are limited (e.g. opening times of a token shop). Specified target behaviors There is a broad range of possible target behaviors: doing self-care such as washing, attending scheduled activities, having good academic behavior, or avoiding disruptive behavior. A token economy is more than just using exchangeable tokens. For a token economy to