resources would soon be depleted and consequently the incentives would be lost. One advantage of tokens is they can be used to divide larger rewards into parts: clients can save tokens to buy more expensive rewards later. This implies they shouldn't immediately spend all earned tokens on attractive smaller rewards, and instead learn to plan ahead. This way they can acquire self-control. (See Delayed gratification.) Individual and group contingencies Many token economies are designed for groups. The system is running for a whole ward or class. Within this group contingency specific individual goals and reinforcers can be added, though sometimes a token economy is designed for only one specific individual. Consistent application The power of a token economy largely depends on the consistency of its application. To achieve this thorough staff training is essential. Some token economies failed exactly on this point. Token economies imply rights and duties for clients as well as for staff. When, according to the system, a client deserves tokens, he or she should get them, even when a staff member judges he or she doesn't deserve them because he has been impolite the day before. Family education and involvement is also an aspect. They can support the system or they can undermine it, for instance by secretly giving undeserved rewards. Leveled system Often, token economies are leveled programs. Clients can pass through different levels until they reach the highest level. At that point, behaviors are performed without token reinforcement. Higher levels require more complex behaviors. The incentive to progress from one level to the next is the availability of increasingly desirable reinforcers. History In the early 19th century, long before there was any knowledge about operant learning, there were some precursors of token economies in schools and prisons. In those systems points could be earned and exchanged for many different items and privileges. Only in the 1960s the first real token economies arose in psychiatric hospitals. Teodoro Ayllon, Nathan Azrin and Leonard Krasner were important pioneers in these early years. The very first token economy bearing that name was founded by Ayllon and Azrin in 1961 at Anna State Hospital in Illinois. In the 1970s the token economies came to a peak and became widespread. In 1977 a major study (a randomized controlled trial), still considered a landmark, was published. This study showed the superiority of a token economy compared to standard treatment and specialized