Although no one knows for sure how phobia develop, some researchers believe that phobia are passed from parents to children in one of two ways: either by inheriting the gene for a phobia, or by observing a parent's phobic reaction to something and learning to react in the same way. Another possibility is that phobia are a reaction to something frightening a person may have previously experienced. For example, John Dickson could have develpoed his fear of dog (cynophobia) when , as a child, he saw a dog bite another child.