1. Wechsler Adult Intelligence Scale (WAIS) is one of the most commonly used IQ tests and was initially developed in 1949. There is also a version for children. The test includes two groups of subtests: Verbal and Performance. Verbal scales measure general knowledge, language, reasoning, and memory skills. Performance measures spatial, sequencing and problem-solving skills. Each test is individually administered by a trained examiner and requires a complex set of test materials. It takes about 90 minutes to complete. The test includes a range of question types, including comprehension, vocabulary, digit span, arithmetic, pectoral questions, block/matrix questions. The WAIS measures both crystallised and fluid intelligence.