Which of the following best exemplifies positive reinforcement?

Positive reinforcement is a concept in behavioral psychology that involves the addition of a stimulus to encourage a desired behavior. In this context, giving a gold star for raising hands in class effectively demonstrates positive reinforcement because it provides a reward that acknowledges and encourages the behavior of participation. This approach not only reinforces the act of raising hands but also fosters an environment where students feel motivated to engage more actively in classroom activities.

In contrast, the other options reflect different behavioral strategies. Taking away chores for good grades represents a form of negative reinforcement, where a negative condition is removed to increase a desired behavior (studying or getting good grades). Enforcing a curfew is a form of punishment or control designed to modify behavior rather than reinforce positive behavior. Increasing homework for poor performance is also a punitive measure intended to discourage poor academic performance, rather than promoting positive behavior through encouragement. Therefore, the option that illustrates positive reinforcement most clearly is the one involving the gold star for raising hands in class.