Final answer:
Negative reinforcers and primary reinforcers both increase behaviors, but through different mechanisms. Negative reinforcers remove something aversive, while primary reinforcers satisfy basic biological needs.
Step-by-step explanation:
The question asks about which type of reinforcer works to increase the likelihood that a behavior will be strengthened. In the field of operant conditioning, all reinforcers are designed to increase the likelihood of a behavior occurring. Among the options provided, negative reinforcers and primary reinforcers both function to increase behaviors, but their mechanisms differ.
A negative reinforcer is the removal of an aversive stimulus to increase the likelihood of a behavior repeating, which can strengthen the behavior. A primary reinforcer is inherently valuable and satisfies a basic biological need, such as food or water, which can also increase the likelihood of a behavior being repeated. Since primary reinforcers address innate needs, they are typically more immediately effective at strengthening a behavior compared to secondary or delayed reinforcers.