Psychology MCAT Practice Exam

A primary reinforcer is a stimulus that naturally reinforces behavior without prior learning or conditioning. It satisfies a biological need or drive. In this case, food exemplifies a primary reinforcer because it fulfills a basic necessity for survival. When an organism receives food, it experiences a direct, immediate benefit, which often encourages the behavior that led to obtaining the food.

The other options do not fit the definition of primary reinforcers as they require some form of learning or societal agreement to gain their reinforcing properties. Money, for instance, serves as a secondary reinforcer that acquires its value through its association with the ability to purchase primary reinforcers like food. Similarly, grades in school and tokens are also secondary reinforcers; they derive their reinforcing qualities from the benefits they can provide, such as rewards or privileges, but do not satisfy any inherent biological need directly.