Raven's Progressive Matrices (often referred to simply as Raven's Matrices) or RPM is a nonverbal test typically used to measure general human intelligence and abstract reasoning and is regarded as a non-verbal estimate of fluid intelligence. It is one of the most common tests administered to both groups and individuals ranging from 5-year-olds to the elderly. It comprises 60 multiple choice questions, listed in order of increasing difficulty. This format is designed to measure the test taker's reasoning ability, the eductive ("meaning-making") component of Spearman's g (g is often referred to as general intelligence). The tests were originally developed by John C. Raven in 1936. In each test item, the subject is asked to identify the missing element that completes a pattern. Many patterns are presented in the form of a 6×6, 4×4, 3×3, or 2×2 matrix, giving the test its name.