Autism is a developmental disability that comes from a neurological disorder that affects the normal functioning of the brain. It is characterized by the abnormal development of communication skills, social skills, and reasoning. Males are affected four times as often as females. Children may appear normal until around the age of 30 months. Autism Symptoms vary widely in severity; include impairment in social interaction, fixation on inanimate objects, inability to communicate normally, and resistance to changes in daily routine. Characteristic traits include lack of eye contact, repetition of words or phrases, unmotivated tantrums, inability to express needs verbally, and insensitivity to pain. Behaviors may change over time. Autistic children often have other disorders of brain function; about two thirds are mentally retarded; over one quarter develops seizures. It remains unclear, but a psychological one has been ruled out. Neurological studies seem to indicate a primary brain dysfunction, and a genetic component is suggested by a pattern of autism in some families. It is largely believed that autism is a genetic disorder that involves several genes related to gene function. However it is unclear to researchers what causes these genes to turn on.