Some preventers only stop an effect when it is being produced by certain causes. For example, nasal spray prevents headaches caused by a cold but not headaches caused by dehydration or stress. Thus, preventers differ in preventative scope: the range of circumstances across which a preventer operates. An experiment indicated that people are sensitive to differences in preventative scope and that participants are more likely to generalize prevention when the preventer has a broad preventative scope. Additional evidence suggested that people take preventative scope into account when attempting to explain how prevention operates.