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History of Intelligence Tests design

IQ (Intelligence Quoficient) or intelligence tests are meant to measure human intelligence. This obviously requires a clear definition of intelligence. Finding a definition for intelligence has however been the tricky part and seems to differ slightly for many.

However, this score is not the main aim of these assessments. Rather, they have been used for determining strengths and weaknesses and finding areas where support is needed. These tests are now just a quick quiz on the internet providing you with a ‘grading.

Instead, these assessments are reliant on the observations of a professional that administer these in a standardised manner.

Intelligence Tests design

The phrase IQ was however coined by the German psychologist, William Stern. Originally an IQ score was attained by dividing mental age (from IQ test) by chronological age. The resulting fraction was then multiplied by 100 to attain an IQ score.

Although the English statistician, Francis Galton made the first attempt at standardized testing, Alfred Binet and Theodore Simon had more success in 1905. The Binet-Simon intelligence scale focused on verbal abilities but used to identify mental retardation in school children.

Weschler Intelligence Scales

Possible uses of the Weschler Intelligence Scales range from assessing people with traumatic brain injuries to those struggling with learning or to identify a gifted child.

IQ tests are carried out by a professional and are not just related to a score. Instead, it is an interpretation of those scores in different areas. These are also standardised tests and have to be administered in a standardised way to assure the results are valid.

One of the most insightful and widely used tests currently is the Weschler Intelligence Scales.

Intelligence test. Woman with picture of cogs representing a brain drawn above her head.

There are in fact, various versions of the Weschler scales.

Weschler Intelligence Test

  1. The Weschler Adult Intelligence Scale (WAIS) for people 16 – 90
  2. The Weschler Intelligence Scale for Children (WISC) for children 6 – 16
  3. Weschler Preschool and Primary Scale of Intelligence (WPPSI) for children 2½–7 years, 7 months
  4. Weschler Achievement Test(WIAT)

Tests and subtests for these different scales are very similar. Therefore descriptions below provide a different aspect of what they each measure.

Adult Weschler Intelligence Test (WAIS-IV)

The WAIS was first published in 1955 as a revision of the Wechsler–Bellevue Intelligence Scale, released in 1939.

The WAIS-IV is divided into 5 scales;

  1. Full Scale
  2. Verbal Comprehension Scale
  3. Perceptual Reasoning (non-verbal) Scale
  4. Working Memory scale
  5. Processing Speed Scale.

Weschler Intelligence Test’s Full Scale

Firstly, the Full Scale gives the person’s relative standing in comparison to age-related peers.  It provides a global estimate of overall cognitive abilities.

Verbal Comprehension Scale

Secondly, the Verbal Comprehension Scale gives an indication of the ability to receive, process, make meaning of, and express information presented verbally and to communicate understanding with words. The Verbal Comprehension Scale score is a good indication of verbal learning potential and a predictor of academic learning/success.

  • Similarities: ‘How are these two words the same?’ It measures verbal concept formation and reasoning.   It also involves crystallized intelligence, abstract reasoning, auditory comprehension, memory, associative and categorical thinking, the distinction between nonessential and essential features, and verbal expression.
  • Vocabulary: It measures an individual’s word knowledge and verbal concept formation.  It also measures an individual’s crystallized intelligence, fund of knowledge, learning ability, long-term memory, and degree of language development.
  • Information: It measures an individual’s ability to acquire, retain, and retrieve general factual knowledge.  It involves crystallized intelligence and also long-term memory.

Perceptual Reasoning Scale

Thirdly, the Perceptual Reasoning Scale gives an indication of the ability to reason non-verbally through the manipulation of concrete materials, visual-motor coordination and also visual concept formation.

  • Block Designs: Measures the ability to analyse and synthesize abstract visual stimuli.  It also involves nonverbal concept formation and reasoning, broad visual intelligence, fluid intelligence, visual perception and organization, simultaneous processing, visual-motor coordination, learning, and the ability to separate figure-ground in visual stimuli.
  • Matrix Reasoning: It involves fluid intelligence, broad visual intelligence, classification and also spatial ability, knowledge of part-whole relationships, simultaneous processing, and perceptual organisation.
  • Visual Puzzles: It measures nonverbal reasoning and also the ability to analyse and synthesize abstract visual stimuli.

Working Memory Scale

Also, the Working Memory assesses an individual’s numerical ability as well as their ability for sequential processing.  It involves the handling of numbers or letters in a step by step sequential fashion with a good and non-distractible attention span.

  • Digit Span‘s 3 sub-tests:
    • Digit Span Forwards: repeating a sequence of numbers forwards. This also involves rote learning and memory, attention, encoding, and auditory processing.
    • The Digit Span Backward: repeating a sequence of numbers backwards. This also involves working memory, the transformation of information, mental manipulation, and also visuospatial imaging. 
    • Digit Span Sequencing also measures working memory and mental manipulation.
  • Arithmetic: It involves mental manipulation, concentration, attention, short- and long-term memory, numerical reasoning ability, and also mental alertness.

Processing Speed Scale

Lastly, Processing Speed measures an individual’s response speed in solving a variety of verbal and nonverbal problems.  In other words, Processing Speed indicates how quickly one can process the information received and then the subsequent response.

  • Symbol Search: It measures processing speed, short-term visual memory, visual-motor coordination, cognitive flexibility, visual discrimination, psychomotor speed, speed of mental operation, attention, and concentration.  It also measures auditory comprehension, perceptual organization, fluid intelligence, and planning and learning ability.
  • Coding: It measures processing speed, short-term visual memory, learning ability, psychomotor speed, visual perception, visual-coordination, visual scanning ability, cognitive flexibility, attention, concentration, and motivation.

Supplemental Tests

There are also four supplemental tests for interpretation. Therefore, one test for each scale. These, however, do not form part of the Full Intelligence Scale.

  • Comprehension (Verbal Comprehension): Measuring verbal reasoning and conceptualization, verbal comprehension and expression, the ability to evaluate and use past experience, and the ability to demonstrate practical knowledge and judgement.  It also involves crystallized intelligence, knowledge of conventional standards of behaviour, social judgement, long-term memory, and common sense.
  • Figure Weights (Perceptual Reasoning) 16-69 only: It measures quantitative, analogical reasoning, and also working memory.  
  • Picture Completion (Perceptual Reasoning): Designed to measure visual perception and organization, concentration, and therefore visual recognition of essential details of objects.
  • Letter-number Sequencing (Working Memory): This task involves sequential processing, mental manipulation, attention, concentration, memory span, and short-term auditory memory. It may also involve information processing, cognitive flexibility, and fluid intelligence.
  • Cancellation (Processing Speed): It measures processing speed, visual selective attention, vigilance, perceptual speed, and also visual-motor ability.

Intelligence Tests

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