Neuropsychology is a science that studies how the brain and nervous system (the body's electrical wiring) affect a person's behavior, thoughts, and feelings. It looks at how physical changes in the brain, such as injury or illness, can cause problems in thinking, feeling, and behaving. Neuropsychologists do tests and studies to learn more about the way the brain works, and figure out what might be causing difficulties with thinking, feeling, and behavior. They also look for ways to help people with these difficulties.