Luis developed a conditioned fear response to a specific breed of dog as a result of having been bitten by one when he was six years old. The fact that Luis is not afraid of all types of dogs can best be explained by which of the following principles?

Negative reinforcement involves the strengthening of behavior through the removal of an unpleasant stimulus. In this scenario, Luis's fear response does not create a situation where he avoids an unpleasant experience; instead, it is a learned response specifically related to the breed of dog that caused him harm. Thus, negative reinforcement does not accurately explain his selective fear.

Successive approximations refer to the gradual shaping of behavior by rewarding closer and closer approximations to a desired behavior. This concept is more relevant in behavior modification techniques and does not apply to Luis's fear response. His fear is not shaped by rewards for specific behaviors but rather is a direct response to a traumatic experience.

Stimulus generalization occurs when a conditioned response is triggered by stimuli that are similar to the original conditioned stimulus. While this might suggest that Luis could fear all dogs, he does not; instead, he only fears a specific breed. Therefore, stimulus generalization does not explain why he differentiates between breeds.