BASIC (08-00)

A. General

In the adjudication of cases involving alleged intellectual disability, accurate information pertaining to the claimant's daily activities and current behavior is required in order to determine the level of impairment severity. In instances of severe intellectual disability, such information may preclude the need for standardized test results altogether. Standardized test results are not required in cases of intellectual disability which unequivocally meet or equal Listing 12.05A or 112.05A. intellectual disability must be manifested by severe mental and social incapacity as evidenced by marked dependence upon others for personal needs (e.g., toileting, eating, dressing, or bathing) and inability to follow directions such that the use of standardized measures of intellectual functioning is precluded. Standardized intelligence test results are essential to the adjudication of all other cases of alleged intellectual disability.

The specific test administered should be reliable (yield repeatable results), valid (be an accurate measure of what is meant by intellectual ability or intelligence), and be standardized according to accepted psychometric practice and have normative data relating to a recent cross-section of the general population. It is also necessary for the particular test to sample a wide range of the subject's skills and abilities rather than being limited to measuring only one or a few narrow intellectual functions. Tests markedly deficient in one or more of the foregoing qualities should be avoided for purposes of evaluating disability.

Moreover, it should be clearly understood that different tests may not yield identical (or even similar) “IQ” results. The IQ requirements denoting a disabling impairment under the Listing of Impairments are meant for application in conjunction with tests of general intelligence having IQ means of approximately 100 and standard deviations of approximately 15 in the general population at large (e.g., the Wechsler series (WAIS-R, WAIS-III, WISC-R, WISC-III, WPPSI, and WPPSI-R and the revised Stanford-Binet scales.)

NOTE: The Stanford-Binet IV is preferred over the earlier LM edition because of the updated and enlarged normative sample.

Thus, IQ's below 60 would reflect a level of intellectual functioning below that of 99.5 percent of the general population. IQ results of tests with parameters other than the above would obviously require special transformation in order to render them comparable to the requirements stated in the Listings.

If a file contains the results of several versions of the same test, such factor as currency of the evaluation, claimant's age at time of evaluation, adequacy of claimant and evaluator motivation, and completeness of the administration and report must also be weighed in the decision as to which of several IQ's from different revisions of the same measure will be determinative.

It is obviously important to know what test was administered, the date the test was administered, the age of the subject at the time the test was given, whether the results are applicable to the subject's current condition, and the qualifications of the examiner. Adequate resolution of the issues posed by specific cases may require professional consultation with a clinical psychologist or psychiatrist trained in intelligence test administration and interpretation. At the hearing level, the testimony of a medical or psychological advisor or vocational expert may be required.

Inclusion of subtest scores in conjunction with the Wechsler scales is always desirable in the assessment of mental deficiency because it:

1. Provides evidence that the entire battery of subtests was administered rather than a less reliable “short-form;”

2. Provides clues to a possible invalidity of test results or to possible errors in computing IQ scores; and

3. Permits the evaluation of intellectual strengths and weakness that may have a bearing on capacity to work where a determination cannot be made on the basis of medical considerations alone.

Moreover, reporting of subtest scores is essential in cases where cognitive deficits require assessment (e.g., chronic brain syndrome or “organicity” due to injury or disease). Since the pattern of subtest scores is most useful in providing medical evidence (signs and laboratory findings) regarding such alleged deficits, inclusion of subtest scores in such cases is required.

The absence of subtest scores in reports of psychological testing performed independently of social security disability evaluation does not necessarily mean that a proper determination or decision cannot be made without them. However, since it cannot be reliably determined in advance when subtest scores will be required in connection with intellectual evaluation, subtest scores should be requested when arranging to purchase consultative psychological examinations involving the Wechsler scales. In the occasional situation where administration of certain tests, subtests, or subscales may be neither feasible nor valid because of the individual’s background, condition, or circumstances, it should be requested that an explanation for this limitation be included in the report. If test results (including subtest scores) are not included they should be requested, and if unavailable, further testing may be required.

Test results obtained at younger ages are less reliable and valid than test results obtained at older ages. Results obtained below the age of 6 are particularly suspect. The test results should be consistent with the child's behavior and daily activities as reflected in the evidence of record, including reports of disability interviews or observations or testimony at the hearing. When there are inconsistencies further documentation may be required to resolve these differences. While there is obviously no specific age at which test results suddenly become “valid” (i.e., accurate and stable indices of the subject's abilities), IQ's obtained from tests having the desirable qualities described above tend to stabilize by the age of 16.

B. Verbal and Nonverbal Measures of Intelligence

Section 12.00D and 112.00B of the Listing of Impairments describe the circumstances under which one or another of the various standardized measures of intelligence is appropriate. Intellectual abilities can generally be assigned to either of two broad categories: verbal and nonverbal (performance). Certain measures of intellectual functioning are almost exclusively verbal (e.g., the Revised Stanford-Binet Scale). Other acceptable measures of general intellectual functioning are almost exclusively nonverbal (e.g., the Raven Progressive Matrices). The Wechsler scales incorporate both verbal and nonverbal sections and yield separate IQ's for each.

For the majority of persons, scores on verbal measures tend to be highly correlated with scores on nonverbal measures, even though two, somewhat different, broad facets of intellectual functioning are involved. However, both are relevant to the determination of impairment severity.

In tests containing both verbal and performance sections, an individual may attain a marginally higher score (or in rare instances, even an appreciably higher score) on one component than on the other, but this in no way alters the fact that the severity of impaired intellectual functioning is denoted by the lower of the two scores. The full scale IQ, on the other hand, is usually a statistical average of the two, although in rare instances it can be higher (or lower) than either. Accordingly, where appropriate intelligence testing yields verbal, performance and full scale IQ's, the lowest result of the three will be determinative of impairment severity.

C. Validity of Repeated IQ Testing Results

This section discusses the effect of practice which occurs with repeated use of the same intelligence test.

An estimate of the significance of an IQ score which improves on retesting with the same instrument requires knowledge of score variations which may occur due to imperfect test reliability and stability. The reliability of the score can be determined through the statistical concept of standard error of measurement (SEm) as reported in the tests' manual. The SEm is a standard deviation unit defining the degree of chance error for any particular score. It permits as estimation of the true score value based on the actual score obtained on testing. To be considered significant, an improved IQ score obtained at retest must exceed one SEm.

Practice related increments in IQ of 1 SEm are common for retest intervals of 1 year or less. The size of the practice effort decreases as the retest interval lengthens. When an IQ score improves at retest, the score increases must exceed the expected practice effort before a less severe impairment can be validly established. The magnitude of the expected effect is probably most accurately determined by reference to published studies most appropriate to the specific situations (e.g., test administered, age of claimant).

D. Testing of Children

1. Recency of IQ Testing

It is of the utmost importance in evaluating mental deficiency that IQ test results be sufficiently current to give an accurate and realistic picture of mental capacity. As indicated in section 112.00B of Part B of the Listing of Impairments, the necessary evidence in cases involving children with intellectual disability includes, in addition to the results of applicable standardized psychological tests, observations by professional workers and information concerning daily activities and past and present behavior.

In evaluating whether IQ test results obtained before age 16 are sufficiently current to permit adjudication, both the child's age at the time of testing and the test results themselves should be considered. While reliability and validity are in part dependent on age at testing, very low IQ's are less likely to increase to a point in excess of 59 (at which point an individual would have an impairment that no longer meets or equals the Listing on the basis of IQ alone).

In determining whether IQ test results are sufficiently current to permit disability evaluation, the following may be considered as general guides:

In some circumstances, a fully favorable determination can be made in cases of intellectual disability under listing 112.05 with IQ test scores that are not “current” under the general recency guides presented above. See DI 24501.016 for an explanation of these circumstances.

Intelligence test results obtained at age 16 or older may be assumed to apply to the subject's current status provided they are compatible with the individual's current behavior. However, when test results obtained in the past are incompatible with current behavior, current testing will be required. Current testing may also be required where the IQ results at hand fall within the range which requires an assessment of vocational factors. Such current testing (WAIS as well as other appropriate tests) may be needed to determine whether the individual can engage in any substantial gainful activity.

2. Evaluating Developmental Milestone Criteria

Developmental milestone criteria are used for determining disability when a child's young age or condition precludes formal standardized testing. Developmental milestones cannot be applied in as exacting a manner as IQ listing and the results must be considered in combination with professional observations of a child's performance, behavior, and activities.

The scoring of milestone achievements must be recorded by a professional experienced in testing or evaluating children using standardized criteria. Statements of behavior or capabilities by relative or other parties do not substitute for professional observation.

The demonstration that a child has achieved only those milestones typically acquired by a child one-half its age is useful only where those findings are consistent with the child's daily activities and with professional observations of the child's performance and behavior. Should a professional, skilled in the evaluation and testing of children, conclude these to be consistent, then the criteria for disability under 112.05A would be met.

Where the child's achievement of some milestones is somewhat greater than expected or a child one-half the subject child's age, greater weight is to be given to daily activities and to direct observations by professionals in deriving conclusions concerning the overall impairment. In such situations, where a professional concludes that observations or activities reflect a developmental deficiency below that suggested by the recorded milestone achievements, the conclusions may be drawn that the criteria of 112.05A are met or equaled.