What is sensitization?

Sensitization is indeed characterized by an increase in responsiveness following exposure to a stimulus. This psychological phenomenon occurs when an individual becomes more sensitive to a stimulus after it's presented repeatedly, particularly if the stimulus is intense or noxious. For example, after experiencing a traumatic event, a person might have heightened reactions to stimuli that remind them of the event, leading to increased anxiety or startle responses.

The key aspect of sensitization is that it is a form of non-associative learning, where repeated exposure to a stimulus causes stronger reactions to that particular stimulus or related stimuli. This process is important in understanding how individuals can develop heightened awareness or stress responses, especially in the context of trauma or chronic stress.

In contrast, the other options describe different concepts: a decrease in responsiveness refers to habituation, while learning in natural environments relates to experiential learning, and negative behavior towards a stimulus speaks to aversion, which involves associative learning rather than the non-associative processes involved in sensitization.