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Choosing Assessment Instruments

When the professional determines that testing or retesting is necessary, that person is usually limited to using whatever instruments are readily available. The most typical intellectual battery is the Wechsler scales' verbal subtests. Performance items are usually not administered, and if they are, should be used as a way of observing the process of problem solving rather than to obtain an actual IQ score. Keeping in mind that success on intelligence tests is highly dependent on language and experience, and that 70- 80% of all learning takes place through the visual mode, careful interpretation of test results is warranted.

Interpreting Results

Analysis of Weschler subtest results may yield the following:

  • Information - Scores may be depressed because of lack of visual experience or reliance on sighted persons' interpretations of the environment.
  • Similarities - Telling likenesses and differences between two concrete items may be a skill that is over taught to visually impaired students, which could artificially inflate scores. Abstract items are more difficult conceptually to grasp because of lack of vision and experience.
  • Vocabulary - For children who are very verbal, a large vocabulary of memorized, rote definitions alone is not an indication of superior intellectual functioning. Some children exhibit certain degrees of echolalia, or use speech without meaningful experiences to support them.
  • Comprehension - Social experiences and social skills are largely learned by experience and imitation. The visually impaired child cannot "size up" a situation visually as sighted children do and must be specifically taught what to do in certain situations.
  • Arithmetic - The ability to remember and manipulate mathematical operations without a visual image or special tools may put the child with a visual impairment at a disadvantage. Timing requirement is usually eliminated from this subtest for the visually impaired.
  • Digit Span - Scores may be inflated if the visually impaired child has highly developed auditory memory skills for unrelated items. On the WAIS III, verbal IQ score may be inflated or reflect a pseudo- increase since the digit span score is calculated into the verbal IQ where It is not on the Children's scales (WISC III). Conversely, if there is a problem with short term auditory memory, scores will be lower.

Adaptive Behavior

Although adaptive behavior assessments are not required, except in cases where other handicapping conditions are being considered or reassessed, the particular areas of adaptive behavior are often those that need remediation and intervention with the visually impaired child. Functioning levels in the areas of daily living skills, communication, and socialization are frequently ones which are depressed in this population. A measure of adaptive behavior such as the Vineland Adaptive Behavior Scales can be helpful in identifying areas in need of IEP goals. This particular instrument does include some norms for visually impaired children (ages 6- 12 in residential settings). Since the Vineland is in an interview format, input from the parent AND the teacher or primary care giver is important. Consultation with the VI teacher is also helpful in interpreting results.

Another interview format adaptive behavior assessment instrument which is used by TDMHMR (Texas Department of Mental Health and Mental Retardation) Is the Inventory for Client and Agency Planning (ICAP) 1988, available from Riverside Publishing. Skill areas measured include: Motor, Social and Communication, Personal Living, and Community Living.

Criterion Referenced Assessments

When standardized assessment instruments cannot be used, the evaluator is allowed to use whatever instruments are necessary in order to determine the student's level of functioning. In using developmental checklists, the evaluator is reminded to interpret results with caution, as the development of visually impaired children, especially those who are totally blind, is different from sighted children. One Instrument, the Developmental Activities Screening Inventory (DASD, has suggestions for adapting assessment items for visually impaired, although it does not include this population in the normative data.

Bulla, 2002

Interpreting Test Results And Observations

In analysis and interpretation of both test results and clinical observations, keep the following in mind as you review these with a teacher of the visually impaired:

  • Don't assume that a large vocabulary alone is an indicator of giftedness. Be alert to use of verbalisms and echolalia and consult with a speech/language therapist when in doubt.
  • Don't assume that confusion of pronouns and presence of self- stimulatory behaviors are indicative of a pervasive developmental disorder.
  • Don't assume that a learning disability or motivational problem exists when a discrepancy in level of Intelligence and achievement are noted. Similarly, poor spelling skills and poor penmanship are not indicative of a learning disability, or just plain "laziness".
  • Don't assume that emotional problems can always be diagnosed separately or apart from the visual impairment.
  • Don't assume that efficient performance in the general environment (playground, hallways, etc.) implies similarly efficient performance in the classroom.

Loftin, 2002