Which of the following best defines an establishing operation?

An establishing operation is a concept from behavior analysis that refers to any condition that alters the effectiveness of a reinforcer or punisher, typically by increasing the desire for a specific stimulus or outcome. When an individual experiences an increase in the desirability of a particular stimulus, they become more motivated to engage in behaviors that will lead to access to that stimulus.

Option D captures this essence perfectly as it emphasizes the increase in desirability. For example, if someone is deprived of food for a period, food becomes a much more desirable reinforcer, enhancing the likelihood that specific behaviors leading to food acquisition will occur. This process clarifies why certain conditions can significantly influence behavior by modifying how reinforcing a stimulus might be at that moment. Thus, the correct answer accurately reflects the fundamental principles of establishing operations in behavior analysis.