What characterizes a stimulus as a reinforcer?

A stimulus is characterized as a reinforcer when it increases the likelihood or frequency of a behavior it follows. This effect is central to the principles of reinforcement in behavioral psychology. When a behavior is followed by a stimulus that reinforces it, that behavior becomes more probable to occur in the future.

For instance, if a child receives praise after completing their homework, the child is likely to complete their homework more often in the future because the praise serves as a reinforcing stimulus. This relationship highlights the key concept that the effectiveness of a reinforcer is not based on its inherent qualities but rather on the impact it has on the frequency of a behavior. Reinforcement can take various forms, including positive reinforcement, where a desirable stimulus is presented, or negative reinforcement, where an unpleasant stimulus is removed.

The other choices do not accurately define what constitutes a reinforcer. A reinforcer does not need to provide satisfaction to the provider, nor is it universally accepted by everyone; its effectiveness can vary among individuals. Additionally, while a reinforcer may change the behavior of others, it primarily pertains to the individual whose behavior is being reinforced. Thus, the defining characteristic of a reinforcer is its ability to increase behavioral frequency.