Taking a Look at Intellectual Disability

Intellectual disability can be defined by; “significant impairment of intellectual functioning, significant impairment of adaptive/social functioning and age of onset before adulthood” (British Psychological Society, 2000). As explained by Gordon (2010), an individual can be classified as intellectually disabled (ID) if they score below a 70 on a reliable and standardized IQ test. Professionals rely on The Wechsler Adult Intelligence Scale Third Edition (WAIS-III) and the Wechsler Intelligence Scale for Children Fourth Edition (WISC - IV) to measure IQ among adults and children (Gordon 2010) p 197). These two tests are very popular and have been used in the United States for a number of years.

Strengths.

These tests can help assist counselors by looking and comparing IQ scores of students. By having this valuable information, counselors can determine placement and needs of students. IQ tests don’t measure everything, but like Drummond & Jones (2010) state, “these test measure a broad spectrum of cognitive abilities, such as reasoning, comprehension, judgement, memory, and spatial ability” (p 155). An entire section of the ACA (2005) Code of Ethics covers evaluation, assessment, and interpretation. As stated in the code, “the primary purpose of educational, psychological, and career assessments are to provide measurements that are valid and reliable in either comparative or absolute terms.”

Weaknesses.

The WAIS-III and WISC- IV have been labeled reliable and valid, however; according to Gordon (2010) “there have been some concerns about how accurately these tests measure intellectual functioning at the extreme ends.” Nagle & Lazarus (1979) conducted one evaluation with 30 participants, with IQ’s ranging from 55-75 and enrolled in special education classes to compare the WAIS and the WISC. Gordon (2010) informs readers that the study found WAIS scores to be significantly higher. IQ scores on the WAIS were higher by thirteen points, but there were significant correlations suggesting content was related despite nonequivalence of scores (Gordon (2010) p 197). A study was done to analyze the discrepancy between the scores of the two IQ tests. Another research study was done in the UK with students who were sixteen years of age, were selected from four special education schools, and had to speak English (Gordon (2010) p 198). The students tested, according to Gordon, (2010) were seven males and eight females who received informed consent from head teachers at their current school and were administered the WAIS-III UK Edition and the WISC-IV UK Edition. Students were split into two groups, groups one and two, and the group they were assigned to determine which assessment they would take first (Gordon (2010) p 198).