How is intelligence measured? The most widely used test is the Wechsler Adult Intelligence Scale (WAIS). This test makes an important distinction between verbal ability and nonverbal ability. There are separate tasks to measure each type of ability. Scores on these individual tasks are then combined to produce an overall IQ score.

As shown in this table, the WAIS contains 6 verbal subtests and 5 performance (nonverbal) subtests.

Table. There are two columns. The column labelled 'Verbal Subtests' contains: 'Information: Answer general-knowledge questions', 'Digit Span: Repeat a list of numbers', 'Vocabulary: Define words', 'Arithmetic: Solve math problems', 'Comprehension: Explain common proverbs or situations', 'Similarities: Explain analogies'. The column labelled 'Performance Subtests' contains: 'Picture Completion: Identify the missing part of a picture', 'Picture Arrangement: Organize pictures to tell a story', 'Block Design: Arrange blocks to match a design', 'Object Assembly: Arrange puzzle pieces to form a picture', 'Digit Symbol: Use a code to translate symbols into numbers'.

On the next screens you will try your hand at sample questions and tasks similar to the items on each of the 11 WAIS subtests.