Intelligence testing for the visually impaired

 
A variety of IQ tests are available for the visually impaired. Many tests are adaptations of instruments that are in use for the sighted while others are designed specifically for the visually impaired. There are tests that examine verbal IQ or performance IQ or both. Many of these tests are regarded as accurate predictors of success in the workplace and indicators of academic abilities.

Testing conditions

The following conditions are necessary for establishing a successful testing environment
  • An appropriate testing environment is one where there are few distractions and adequate lighting.
  • The examinee should be allowed time to become comfortable and familiar with the room setting.
  • The examiner must take some time in order to describe any testing materials that are part of the test.
  • Examinees should be given the opportunity to experience touching the materials before the test starts.
  • Wherever there is typed material it should be represented in large print.
  • Felt-tip pens are preferred to pencils if writing instruments are necessary.
  • If some of the test questions are in Braille then the examiner should enquire about the examinee's Braille reading ability.
  • For verbal sections of the test, an audio tape or a reader who enunciates are required.
  • True/false options are preferable to multiple choice. Multiple choice questions require the test taker to keep all the options in mind continuously.
  • Speed tests and time limits are not appropriate especially when the test involves extensive use of Braille and testing materials.
  • Breaks should be allowed whenever the examinee feels fatigue.

Norms

Normative samples based on the visually impaired are available, however they are sometimes dated. It is important that norms should be random and representative of the general population of the visually impaired. Whatever the case, norms should specify details about the selected group such as amount of vision, age, career and lifestyle.

The predictive ability of a test that uses norms based on a sighted population is questionable. However these tests can still be used by psychologists for qualitative evaluations. In fact there is a trend to use this informal qualitative approach to IQ testing for the visually impaired.

 

 
Tests

- Haptic intelligence test for adult blind

The Haptic intelligence test is is a performance-based intelligence measure for blind and partially sighted adults and can be completed in up to an hour and a half. It is a tactile performance test and was designed to be used with, or independently of, the verbal scale of the WAIS. It can therefore be used as a replacement of the performance subtests of the WAIS for people who have no usable vision. In fact Wechsler's procedures were followed in the statistical treatment of the data and in establishing age categories.

It consists of the following subtests

  • Dot symbol: analyzing dot patterns
  • Object assembly: assembling puzzle parts such as cubes
  • Pattern board: examining and reproducing peg board patterns
  • Bead arithmetic: solving arithmetic problems on an abacus
  • Object completion: identification of the missing part of an object, for example, a comb with a missing tooth.
  • Block design: blocks with different sides of varying textures are rearranged to resemble patterns on plates.
  • Digital symbol: Numbers, represented by raised dots, are associated with 6 different geometric forms

 

- Wechsler Adult Intelligence Scale (WAIS)

The verbal WAIS is administered to the visually impaired in the same way that it is administered to the sighted, and mean scores have been show to be equivalent. In addition, no significant differences have been found between the scores of the partially blind and the totally blind, or between congenital and adventitious blindness.

 

- Wechsler Intelligence Scale for Children (WISC)

Verbal scale tests are usually the only ones to be administered from the WISC. In cases when the child has little or no useful vision, the WISC performance tests may underestimate the child's true potential. If necessary, performance IQ can be evaluated qualitatively by observing manipulative tasks such as Braille reading.

Visually impaired children have been shown to score high on digit span, which is regarded as a compensatory skill. Their scores are underestimated in similarities and comprehension, due to the abstract concepts contained in these sections. As with the WAIS, the mean scores of the visually impaired and the sighted are equivalent.

 

- Stanford - Ohwaki - Koh's block design scale test

The Stanford-Ohwaki-Koh's block design scale, developed in 1923, is a modification of the Koh's block design scale. It involves the use of touch in order to differentiate between objects, and takes 1-2 hours to administer. The Stanford-Ohwaki-Koh was normed on a visually handicapped population and results are reported as percentiles and quotient scores. It is a performance IQ measure and one of it's sections can also be found in the WAIS-R. However since the WAIS-R is normed in a different way to the Standord-Ohwaki-Koh, scores should not be compared to each other.

 

- The Blind Learning Aptitude Test (BLAT)

The Blind Learning aptitude test is designed for children of all school grades. It was normed on students enrolled in residential schools 30 years ago, and therefore the norming is considered to be inflated.

The test consists of raised-line symbols, similar to Braille. There are various behavioral tasks and the main theme is being able to differentiate between symbols and make deductions. Many of the tasks are adaptations of items on the culture fair intelligence test, and Raven's progressive matrices.

There have been some issues with the testing materials such as durability and structure. However, the test can be helpful in discovering strengths and weaknesses and can be a useful complement to other tests of intelligence. Qualitative feedback can also be provided by observing a child performing the tasks. Studies have shown that the BLAT is correlated to comprehension and Braille reading speed.

 

- Cognitive test for the blind (CTB)

The CTB assesses cognitive functions including measures of abstract reasoning, auditory language functions, memory and spatial abilities.

Verbal subtests: auditory analysis, immediate digit recall, language comprehension and memory, letter number learning, vocabulary.

Non visual performance subtests: haptic category learning, haptic category memory, haptic memory recognition, pattern recall, spatial analysis

The CTB is an integral component of the comprehensive vocational evaluation system (CVES). The CVES includes an assessment of three major constructs of behavior: verbal-spatial-cognitive, sensorimotor, and emotional-coping.

 

- Interim Hayes-Binet intelligence scale.

Published in 1942, this test makes use of items in the Stanford-Binet intelligence scale that do not require the use of vision. The scales created for both children and adults show high correlations with measures of academic achievement.

 

- The Perkins-Binet

Considered a successor to the Interim Hayes-Binet, the Perkins-Binet contains both verbal IQ and performance IQ items. It was standardized on low vision and blind school children but the norms are now considered to be dated since it was first published in 1980. The test has correlated low with the WISC-R and has been shown to lack reliability. The Perkins-Binet has had issues with confusing test items and has been withdrawn from the market.

 

- Raven's progressive matrices.

Rich and Anderson developed a tactual form of the Raven's colored progressive matrices. High reliability and moderate validity coefficients were reported.

 

- D-48

The tactual version of the D-48 was developed in 1968 by G.Domino. It consists of ordinary three dimensional dominoes and follows the same sequence as the original test. Even though there is no time limit the tasks frustrated some of the examinees. However the results were quite encouraging and correlated significantly with the WAIS verbal tests.

 

- Haptic sensory discrimination test (HSDT)

The HSDT measures functional tactual discrimination and short-term tactual memory.

 

- Slosson Intelligence Test - Revised

The Slosson intelligence test is a verbal intelligence screening test. This test can be administered and scored within 20 minutes and is norm-referenced for ages 4-65

 

- Intelligence test for visually impaired children.

This test examines both verbal and tactile abilities and is published in English, Dutch and German by the Bartimeus Center in Holland.

 

- The Vithoba Paknikars performance test for the blind.

This test measures cognitive behavior through various performance measures.

 

- Haptic Memory Matching Test (HMMT).

The HMMT is used to assess haptic memory and spatial location.

 

-Detroit Test of Learning Aptitude

Scores have been shown to correlate well with the verbal subtests of the Wechsler scales.

 

- Hill performance test of selected positional concepts

The Hill performance test measures the development of spatial concepts in visually-impaired children.

 

- Curriculum guide for deaf-blind and severely multi-handicapped students.

This guide meets the need of those individuals with multiple sensory, mental, orthopedic, neurological and behavior handicapping conditions.

 

- Tactile TONI.

The tactile TONI is a raised-line form of the TONI, graphic performance test. Not yet published.

 

Achievement tests

- Woodcock-Johnson® III Tests of achievement

Woodcock-Johnson® is a diagnostic test used to assess academic and language achievement. It is available in large print through the American printing house for the blind (APH). Braille/tactile editions are also developed by the APH. There is a limited amount of low-level items and therefore the test is not suitable for young students.

 

- SAT and GRE

The SAT and the GRE are college entrance tests and are available in large print and Braille editions. Studies have shown that the mean scores of the visually impaired and the sighted are equivalent as long as the tests are not timed.

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