A secondary reinforcer is a stimulus that becomes reinforcing to an individual through its association with a primary reinforcer. Secondary reinforcers are stimuli that do not have any intrinsic reinforcing value, but that acquire reinforcing value through their association with primary reinforcers. For example, money is a secondary reinforcer because it has no intrinsic value, but it can be exchanged for primary reinforcers such as food, water, and shelter. Secondary reinforcers are often used in operant conditioning, which is a type of learning that occurs through the association of stimuli and responses. Secondary reinforcers can be effective at reinforcing behavior because they can be easily controlled and manipulated, and because they can be used to symbolize and represent primary reinforcers.