Staring into space is a form of dissociation, a state between being asleep and awake. Individuals go into a dissociative state because the nervous system is overly stimulated. Dissociation is a survival mechanism that gives the body a temporary sense of numbness to decrease feelings of distress.
A small amount of stimulation, such as heavy traffic, can put some people into a dissociative state. An individual in such a state may stare ahead blankly without processing what he sees. Being in a dissociative state while driving is known as "highway hypnosis."
To achieve a dissociative state, the body releases opiates into the brain. Chronic dissociation limits perceptions and the ability to interact with others.