Final answer:
Punishment in operant conditioning is used to decrease a behavior by either adding an unpleasant stimulus (positive punishment) or removing a pleasant one (negative punishment). The correct definition is an attempt to weaken a response with something unpleasant.
Step-by-step explanation:
In operant conditioning, punishment refers to the implementation of a consequence in order to decrease a behavior. This can take two forms: positive punishment and negative punishment. Positive punishment involves adding an unpleasant stimulus to decrease a behavior (e.g., scolding a student for texting in class). On the other hand, negative punishment involves removing a pleasant stimulus to decrease a behavior (e.g., taking away a child's favorite toy for misbehavior).
In the context of your question, the correct definition of punishment would be option (C): An attempt to weaken a response by following it with something unpleasant. This is because punishment, whether positive or negative, always aims to reduce the likelihood of a behavior's occurrence. Punishment is different from reinforcement, as all forms of reinforcement seek to increase a behavior rather than decrease it.