From this day on, he avoids driving alone, out of fear that he will be subjected to the same sensation and will lose control, without anyone near him to help him out. Then, this fear may expand to and cover other situations where he might feel ill and the escape from it is difficult, such as in a movie theather. In another example, a woman had a traumatic experience in a car crash. From this day on, she is panick-stricken everytime she is required to board a vehicle and develops a specific phobia to cars. In the first case, what the patient is avoiding is any situation where help might be difficult or complicated, while in the second case, what the patient is avoiding is the object in itself, i.e., the car.
Many neuroscientists believe that there is a clear involvement of biological factors.
For example, functional brain imaging studies have shown that there is an increased blood flow and cell metabolic actiity on the right side of the brain in phobic patients. It has also been demonstrated that identical twins may develop the same type of phobia, even when they were reared separately soon after birth, and educated in different places. It may be also true that human beings are biologically prone to acquire fear of certain noxious animals or situations, sich as rats, poisonous animals, animals with a disgusting appearance, such as frogs, slugs or cockroaches, etc. Two to four shocks were enough to establish a phobia to pictures of spiders or snakes, while a much larger series of shocks was needed to cause phobia to pictures of flowers, for example. One possible explanation is that those fears where originally important for the survival of the human species thousands of years ago and that they lie dormant inside our brains, just waiting to be awaken at any time.