Tests and Measurements
There are several different tests that may be used to evaluate your child. They are not necessarily specific to dyslexia, but when combined they help provide a good picture of your child's development.
Weschler Intelligence Scale
An evaluator will often start with an IQ test to determine your child's overall ability level. One of the most common tests used is the Wechsler Intelligence Scale for Children (WISC III or WISC IV). This test is favored because it breaks down scores into two scales, Verbal and Performance, which in turn each consist of various subtests.
The Verbal Scale measures language expression, comprehension, listening, and the ability to apply these skills to solving problems. The Performance Scale assesses nonverbal problem solving, perceptual organization, speed, and visual-motor proficiency. It includes tasks like puzzles, picture analysis, imitating designs with blocks, and copying. This test is given orally, by an evaluator working individually with your child, so your child does not have to know how to read to score well on the test.
By looking at the scores on various subtests, the evaluator will see a pattern of strengths and weaknesses. This sort of testing is extremely valuable for all children and can be used to indicate a wide variety of learning disabilities. Dyslexia is indicated as a possible diagnosis if the subtests show that a child has particular weaknesses in areas normally associated with dyslexia — such as verbal fluency, short-term auditory memory (digit span), or speed of processing information.
ALERT!
You may be told that dyslexia is a medical term and that you will need a medical doctor to diagnose it. This is not true. Your child's pediatrician may be able to make recommendations and refer you to appropriate specialists, but she will not be able to make a determination as to whether or not your child has dyslexia.
WISC testing will also provide a “full-scale” IQ — the number that results from combining the results of the Verbal and Performance scales. This is useful in evaluating overall cognitive ability and making recommendations for education and therapy. However, caution should be used in interpreting these results as a measure of your child's intellectual capacity.
A very bright child may have a lower-than-expected IQ result due to poor performance on some of the subtests. If a child with a WISC IQ score in the average range scores particularly high on some of the subtests, further testing with other IQ tests is needed to assess for possible giftedness. Your child's emotional state and attitude toward testing could also result in poor performance on this test.
Achievement Tests
Your child will also be given achievement tests to measure reading performance. The specific tests will vary depending on the preferences of the evaluator and the age of your child. Younger children will be given tests that measure pre-reading and early reading skills, such as simple word recognition tests. Older children may be given tests that measure sentence reading, oral fluency, and reading comprehension.
These tests are not the same as the standardized tests that are used in schools to assess classroom performance. Group standardized tests are not valid for measuring individual ability levels because they are designed for purposes of comparing the overall achievement of large groups of children. Although your child's scores on standardized tests may be a relevant piece of information to include in an evaluation, these tests are not a reliable way to diagnose learning disabilities.
Specialized Tests for Dyslexia
There are also some specialized tests geared toward measuring problems commonly associated with dyslexia. For example, a child's ability to parse out the sounds of language can be measured with tests of phonemic awareness. Your child may be asked to read a set of “nonwords” — that is, invented words with no real meaning such as SLIMP or HIFE. He may also be asked to say whether certain words rhyme, or to break apart words by their sounds, such as to say the word “bent” without the “n” sound.
There are also tests given that assess word retrieval skills and auditory and verbal processing speed, that may include tests of rapid automatic naming, which requires the child to quickly read aloud the names of letters or numbers presented on a chart or graph. Short-term memory, or digit span, might also be tested. These tests ask children to remember and repeat a short sequence of letters or numbers or to identify a sequence of letters, numbers, or pictures after briefly viewing a picture or card with such sequence.
