A Who's Who in Pyschometry

Francis Galton, the founding father of modern psychometrics who lived his life as both a geneticist and a meteorologist most of 19th century, was seemingly obsessed with measurement, especially that of mental features called "psychometry". He is credited with laying a foundation for the basic, easy-t0-administer test of mental abilities which led to the creation of our modern intelligence tests. While his colleagues of the time worked tirelessly for formulate laws and principles of mental phenomena applicable to all people, Galton focused solely on the ways people differ from each other. His approach became known as differential psychology. As educators, we must recognize that one purpose of measurement is to identify psychological differences existing between people.

In 1946, Stanley Smith Stevens proposed a definition of measurement as being "the assignment of numerals to objects or events according to some rule." In this very paper, entitled "On the theory of scales and measurement", Stevens also recognized four levels or scales of measurement, including "nominal", "ordinal", "interval", and "ratio". Although the source of much debate, these four types of data are still widely used today, especially in statistics classes throughout the country, where his "normal distribution" receives much attention.

Another pioneer in the field of psychometrics and human intelligence, Louis Leon Thurstone, is most widely recognized for his approach to measurement known as the law of comparative judgement and his ideas surrounding "Primary Mental Abilities". PMAs, essentially, were factors of intelligence that different individuals had in varying degrees. His thoughts on Primary Mental Abilities served as a model for human intelligence that challenged Charles Spearman's then-dominant idea of a single major intelligence factor.

Spearman was the first to offer a psychometric definition of intelligence and is considered the father of classical test theory. His dominant belief was that intelligent behavior was produced by one single quality within the brain or mind and coined this quality "g". Contemporary educators, who are likely proponents of Gardner's Multiple Intelligence Theory, likely would reject this interpretation.

Though there are numerous other "big shots" in the field of psychometrics, these individuals (especially Galton) contributed enormously to the beginnings of the science. Without these early attempts to measure intelligence, teachers today may be without classical test theory and the modern concepts of reliability and validity in evaluating the quality of any test or measurement. More importantly, perhaps, these early scientists have allowed teachers to see the reality behind true individual differences in the intelligences of their students.