For a reinforcer to be considered positive, it must do what?

A positive reinforcer is defined by the addition of a stimulus following a desired behavior that increases the likelihood of that behavior being repeated in the future. In behavioral terms, the introduction of a pleasant or desirable stimulus after a behavior serves to strengthen that behavior.

When a behavior is followed by a positive reinforcer, it creates a favorable consequence for the individual, enhancing the motivation to engage in that behavior again. For example, if a child receives praise (a positive stimulus) for completing their homework, they are more likely to complete their homework in the future.

Regarding the context of the other options, removing a stimulus pertains to negative reinforcement, which aims to increase behavior by taking away an undesirable stimulus. Additionally, while reducing the occurrence of a behavior might relate to punishment, it does not define a positive reinforcer. Lastly, while individual preference can influence whether a stimulus is indeed reinforcing, the fundamental definition of positive reinforcement centers on the addition of a stimulus to strengthen behavior.