Intelligence test (IQ)

Testing and assessment

Intelligence testing was introduced by Alfred Binet and Théodore Simoni in 1905 and this testing has, more recently, been further developed by experts such as Raymond Cattell and Howard Gardner. 

Originally used to assess children who struggled in school, intelligence testing has since been used with young adults and adults, applied to examine individuals of all ages in various contexts. While intelligence testing is still conducted to assess the need for educational support, such testing is now also used in parent competency evaluations, recruitment processes and as part of an assessment for autism or ADHD for children, young adults or adults.

The G-Factor

Extensive statistical analysis has pinpointed the aspects of human functioning most accurately described as expressions of intelligence. In intelligence testing, the aim is to calculate the so-called ‘g-factor’, which represents one’s overall intelligence quotient. The g-factor is based on a factor analysis – or statistical comparison – of a number of different human competencies and functional abilities. Overall, a range of diverse competencies is considered in calculating the g-factor. Examples of competencies include linguistic comprehension and the ability to visually assemble three-dimensional patterns. 

There is a consensus that these and other skills can be quantified, exhibit relative stability over time and represent intelligence when testing children, young adults or adults.

In the most recognized assessment tools, the ones we employ during intelligence testing, the g-factor is calculated based on a person’s abilities in language, working memory, processing speed and visuospatial skills. In each subtest, a raw score is obtained which is then converted into a scaled score. This scaled score can further be transformed into an index score, reflecting an individual’s abilities in a particular area or overall, supporting an assessment of their needs.

The Normal Range for Intelligence

The overall IQ can be used to determine whether a person falls within the normal range, typically with an index score of 85-115, or if the person has special needs or abilities that place them outside this range. In other words, the most common score is 100 and, when testing variability and accepted deviation are considered, the result is a range or index score referred to as “normal”. Even so, deviating from this range is not inherently problematic. A score should be interpreted in the context of a person’s environment and the roles they fulfill.

For us, it is important to utilize both the WISC-V and WAIS-IV during an assessment, since these are the most valid and reliable IQ tests available to determine the need for interventions, assistance or support based on a low or exceptionally high IQ. The specific test used for children, young adults and adults will vary.

WISC – Wechsler Intelligence Scale for Children

The WISC test is used to assess children between the ages of six and 16. It has undergone multiple revisions, culminating in its latest iteration, the 5th edition. Unlike the WISC-IV, the WISC-V also offers a digital version, allowing both the test administrator and the test taker to complete the assessment digitally. The test is available in English and consists of five indexes: Verbal Comprehension Index, Visuo-Spatial Index, Reasoning Index, Working Memory Index and Processing Speed Index. The Reasoning Index is a new addition compared to the previous version of the test. Additionally, the new WISC-V test includes two subtests that have been replaced, as the updated normative data suggests that this enhances the test’s precision in assessing children’s IQ. In addition, beyond a general measure of intelligence, the revised version introduces new indexes, making it easier to analyze an individual’s strengths and weaknesses during an assessment. This is particularly valuable for providing feedback to the test taker, as well as to the family and the school.

>>Learn more about WISC testing for children and adults here

WAIS – Wechsler Adult Intelligence Scale

The WAIS test, also available in English, is used to assess young adults and adults aged 16-90. Like the WISC test for children, the WAIS test comprises different indexes that collectively reflect an individual’s intelligence quotient. The WAIS test is widely used as part of a comprehensive assessment and has recently been released in its 4th edition. Unlike the WISC-V test, the WAIS test does not have a digital version. Furthermore, the WAIS test consists of four indexes: Verbal Comprehension Index, Visuo-Spatial Index, Working Memory Index and Processing Speed Index.

However, the WAIS test remains the best and most recognized tool for measuring intelligence in young adults and adults. It is primarily used in various assessment contexts but can also be employed for Mensa membership evaluations.

Schedule an IQ Testing Appointment

If you are considering having your or a loved one’s intelligence quotient tested and believe it would be beneficial, please feel free to reach out to us. We are always available for a non-binding conversation.