What stimulus increases the likelihood of a desired behavior?

The correct answer is a reinforcer because it is a fundamental concept in behavioral psychology that refers to any stimulus that strengthens or increases the probability of a desired behavior being repeated in the future. Reinforcers can come in various forms, such as rewards, praise, treats, or other positive outcomes that follow a behavior. When a particular behavior is followed by a reinforcer, the likelihood of that behavior occurring again in similar circumstances is enhanced. This process is a key element in establishing positive behavioral patterns, both in animals and humans.

Other terms like motivator or encourager may relate to the overall context of driving behavior, but they do not specifically denote the mechanism of increasing the likelihood of a behavior in the same direct way that reinforcers do. A stabilizer does not apply in this context, as it does not have a defined role in altering behavior likelihood. Reinforcement is the precise term used to describe this motivational aspect in behavior modification.