1) As operation--withholding food, water, sexual contact, etc. Any given program establishes a "level" of deprivation.

2) As process--resulting changes in behavior, usually spoken of as an increasing "state" of deprivation. Any given state is a given "level" of deprivation.

3) An establishing operation, the reduction in the availability of a reinforcer, that increases the effectiveness of the reinforcer. With food reinforcers, two criteria for deprivation levels have been a fixed percentage of free feeding body weight or a fixed period of deprivation after free feeding. Deprivation, also effective for such other reinforcers as a rat's opportunity to run in a running wheel, may be a condition for making any positive reinforcer effective.

4) The frequency with which a person has received a particular reinforcer in the recent past the less frequent the reinforcer, the more deprived the person.

5) The absence or reduction of a reinforcer for a period of time. Deprivation is an establishing operation that increases the effectiveness of the reinforcer and the rate of behavior that produced that reinforcer in the past.

6) The reduced availability of a reinforcer. A student who has not been able to talk with other students f or an hour has had an hour' s deprivation of the social reinforcement of talking with peers.

7) Withholding a reinforcer increases relevant learning and performance.