We, as humans, are very quick to take one bad incident/event, and put it into our heads that every event/incident that comes after that will be just as bad. This is a process called generalization, which is a conditioning process, where we evoke the same or similar response to a conditioned stimulus after the response has been conditioned. The CR will occur in response to a similar stimulus, not just the CS. This is how a lot of fears and phobias can become bigger and worse. If someone had a scary incident involving a specific dog they may develop a fear of all different kinds of dogs, pictures of dogs, or can spiral into developing a fear of animals altogether.