Learning disabilities are traditionally diagnosed by conducting two tests and noticing a significant discrepancy between their scores. These tests are an intelligence (or IQ) test and a standardized achievement (reading, writing, arithmetic) test. Most children found to have a learning disability have normal or above-normal intelligence but do not fully demonstrate that potential on achievement tests. For example, a youngster might score 112 on the full-scale IQ test, but her math score might be 90; this discrepancy of 22 points between her potential ability (IQ) and actual achievement (in math) might qualify her for special services at her school. Some states, for example, define a learning disability as a difference of 15 points, but the criteria for services vary from one part of the country to another. As a result, state-mandated definitions sometimes exclude a range of learning difficulties that do not produce wide discrepancies.
When a learning disability is not detected early, diagnosed correctly, and treated effectively, it can cause a number of other problems. These additional difficulties may be emotional, and a child can show signs of sadness, frustration, or disappointment. Behavior problems like acting out might occur. Or the learning problems may show up within the family, causing, for example, misunderstandings, increased stress, or blaming others. Studies show that among children whose families seek professional help for emotional or behavioral problems, 30 to 50 percent of them have learning disabilities.