In response to an unknown trigger, the immune system may begin producing antibodies that instead of fighting infections, attack the body's own tissues. Treatment for autoimmune diseases generally focuses on reducing immune system activity.
What's taught in school. Some of the items in standardized achievement tests measure the knowledge or skills that students learn in school. In certain subject areas, such as mathematics, children learn in school most of what they know about a subject.
Standardized IQ tests (such as the WAIS and the Stanford-Binet Intelligence Scales) do meet these stringent standards of reliability. To the greatest extent possible, the tests endeavor to control for mitigating variables, but it's an imperfect science and results can be somewhat skewed by individual factors.