Exams and Tests

A psychologist is able to diagnose a cognitive deficit by conducting series of tests that assess the cognitive development of the child.

• IQ (intelligence quotient) test: IQ tests typically include an assessment of memory, language development, problem solving, spatial ability, visual-motor skills, and mathematic reasoning. A test of intelligence does not produce a stable result until a child is six to eight years of age; cognitive tests can be administered prior to this time, but the scores should be interpreted with caution as the scores may change with age.

• Bayley Scales of Infant Development: This test might be used to assess development in infants.

• Stanford-Binet Intelligence Scale or the revised Wechsler Preschool and Primary Scale of Intelligence (WPPSI-R): These tests may be used to assess cognitive ability in preschoolers.

• Wechsler Intelligence Scale for Children (WISC-IV): This intelligence test is most commonly used to assess cognitive development in school-aged children.

In addition to cognitive testing, an assessment of adaptive function is necessary. The Vineland Adaptive Behavior Scales measure a child's level of independent functioning, providing a percentile score that compares the child to other children of similar age.

In addition to cognitive and adaptive function tests, a doctor might recommend a medical evaluation. This may include hearing and vision tests and lab tests, such as a blood lead level test, a screening for thyroid function, a high-resolution chromosome analysis, a DNA probe for fragile X syndrome, or all of the above. An MRI of the brain may be necessary to look for differences in the brain that might help explain a cognitive deficit. Sometimes, a consultation with a geneticist might be helpful to determine if the child has a genetic syndrome and, if so, to help in family planning.