A phobia can be described as a persistent and irrational fear that is associated with the presence or anticipation of a specific object or situation. Avoidance, as in agoraphobia, is an important component of the definition of a phobia. AS in the case of OCD, the individual must realize that the fear is uncommon in order to meet diagnostic criteria. Yet, unlike OCD, both personal distress and functional impairment must be present. Social phobias are centered on the persistent fear of social situations that might expose the individual to scrutiny and evaluation by others, such as a fear of public speaking. There are four types of specific phobias: animal, natural/environmental, blood injection-injury type, and situational type. The difference between environmental and natural centers on whether or not the situation is simply encountered as part of nature or whether it is man-made. The age of onset for developing phobias ranges from very young to childhood. The likelihood of women developing phobias is about 75 to 90 percent higher than males in all except for the blood injection-injury type. These gender differences may be accounted for by the sociological consideration that it is more acceptable for women to have phobias than men. To explain the exception in the case of blood injection-injury type phobias, women are usually more often exposed to blood (such as during monthly periods of menstruation) than men, and are therefore less likely to develop a fear of blood. About 10 percent of the population suffers from some type of social or specific phobia.