When a teacher rewards a student with a pencil for good performance, which reinforcement is being demonstrated?

The scenario presented illustrates positive reinforcement. This occurs when a desirable stimulus, in this case, a pencil, is presented following a specific behavior, such as a student's good performance. The purpose of the reward is to encourage the student to continue exhibiting the desired behavior in the future. Positive reinforcement enhances the likelihood of the behavior being repeated because it adds a positive consequence that the student values.

In contrast, negative reinforcement involves the removal of an unpleasant stimulus to strengthen a behavior, which is not applicable here as the teacher is providing a reward rather than removing something undesirable. Punishment refers to introducing an adverse consequence to decrease the likelihood of a behavior reoccurring, which does not align with rewarding good performance. Extinction involves the cessation of reinforcement for a behavior, which would lead to a decrease in that behavior over time; this is also not relevant in the context given, as a reward is being provided. Hence, the action of rewarding the student with a pencil exemplifies positive reinforcement effectively.