David Wechsler, an American psychologist, defined intelligence as the ability to carry out rational mental processes, to perform actions on purpose, and to interact with surroundings logically. Keeping the elements in mind, he was able to pinpoint a number of drawbacks of Alfred Binet’s Intelligence Quotient (IQ) test, which was the prototype for similar assessment tools. He made respective modifications and published the first version of Wechsler Adult Intelligence Scale (WAIS) in 1955. He appreciated the factors which were irrelevant to intelligence but could potentially affect the examination results, such as a test taker’s nervousness and reading speed. The test assessed separate aspects of intelligence and then generated overall scores, in contrast with Binet’s single score, by taking interdependence into account.
WAIS has evolved over time and the fourth edition has become the most widely recognized and administered instrument for measuring an individual’s IQ, in spite of criticisms about the deviations from Wechsler’s original ideations. There are a total of four test domains, which consist of a certain number of core and supplemental tests as shown below.
Verbal Comprehension
- Similarities – The subject has to point out in what way a word can be likened to another.
- Vocabulary – The nominal capacity is evaluated by showing illustrations to the subject.
- Information – Knowledge which is perceived to be commonly accepted is tested.
- Comprehension – Social scenarios which are frequently encountered in everyday life are simulated.
Perceptual Reasoning
- Block Design – The subject is asked to reconstruct and mimic an illustration or model as closely as possible by making use of blocks.
- Matrix Reasoning – The subject is presented with a matrix and the task is to extend the sequence in a sensible manner.
- Visual Puzzles – The subject has to pick one among three choices so that the presented puzzle can be reproduced.
- Figure Weights – A weight has to be chosen in an attempt to balance a scale.
- Picture Completion – The subject has to deduce the omitted component(s) within an illustration(s).
Working Memory
- Digit Span – A series of numbers are enunciated and the subject has to repeat them in a forward or backward order with or without further arrangements as instructed.
- Arithmetic – The subject has to tackle mathematical questions by means of unvoiced calculations.
- Letter-Number Sequencing – A sequence of characters and digits are enunciated and the subject has to repeat them in alphabetical or ascending order.
Processing Speed
- Coding – Given a printed key, the subject has to replicate symbols which correspond to assigned numerals.
- Symbol Search – Having been presented with a collection of symbols, the subject is asked to determine if any of the symbols in the second collection is duplicated.
- Cancellation – The subject has to cross out specific shapes out of a set.
An average person is expected to score 100 points on WAIS.