What type of reinforcers are inherently rewarding stimuli, such as food and shelter?

Primary reinforcers are intrinsically rewarding stimuli that directly satisfy biological needs and drives, making them essential for survival. Examples include food, water, and shelter; these items fulfill basic human needs and have a natural value due to their role in sustaining life. Because they do not require any learning or conditioning to be seen as rewarding, they are fundamental in the context of operant conditioning and behavior modification.

In contrast, secondary reinforcers acquire their value through association with primary reinforcers; they are not inherently rewarding but become so due to learning (such as money or praise). Vicarious reinforcers involve observing the reinforcement of others' behavior, leading to a change in one's own behavior. Social reinforcers include verbal approval or affection from others and, like secondary reinforcers, derive their value from social contexts rather than biological necessity.