## (Essay found in Nesselroade & Grimm, 2019; pgs. 532 – 533)

Karl Pearson was born in London in 1857, two years before Darwin published *Origin of Species, *a work that would shape Pearson’s entire academic life. It is reasonable to consider Pearson the father of modern statistics. Pearson completed the work on correlation that Galton had started, arriving at the coefficient that bears his name (the Pearson product-moment correlation). He subsequently devised formulas for computing correlations for variables that are noncontinuous (see Chapter 18). Pearson is responsible for many of the concepts and statistical terms that were introduced earlier in this book: the histogram, mode, and standard deviation. He also invented the chi-square test (see Chapter 17).

Karl Pearson believed himself to have been a careful thinker from the beginning of his life. He claimed his earliest memory has him sitting in a high chair, sucking his thumb when someone urged him to stop, so his thumb would not wither away. Upon examining both thumbs he thought, “I can’t see that the thumb I suck is any smaller than the other; I wonder if she could be lying to me” (Walker, 1968, p. 497).

Pearson’s abiding belief in the importance of observation, if not his rejection of authority, guided his lifelong pursuit: the development of mathematical tools that could be used to test the theory of evolution. Over his lifetime, he published more than 500 works. When asked how he found the time to publish so much, he offered, “You Americans would not understand, but I never answer a telephone or attend a committee meeting” (Stouffer, 1958, p. 25).

After earning a degree in mathematics at King’s College, Cambridge, Pearson studied law, and subsequently established a private practice for three years. In 1884, he abandoned law, became a professor of mathematics at University College London, and began his illustrious career. The first major influence on Pearson’s thinking was a book published by Sir Francis Galton, *Natural Inheritance. *Although Pearson was never a formal student of Galton’s, he became his disciple and defender. Pearson was looking for a model of semi-determinism as an alternative to what he believed was the biological sciences’ rigid adherence to causality. He found this semi-determinism in the concept of the correlation. For Pearson, the correlation represented a fundamental paradigm shift, which, he believed, would revolutionize the biological, as well as the social sciences. Researchers could use the correlation as an important measure of the “degree of relatedness” between two variables without having the strict determinist’s burden of claiming causality. In 1896, Pearson introduced the formula that we now use to compute the correlation between two continuous measures. [As an historical aside, the Pearson formula was actually first published a year earlier by Yule (1895), a student of Pearson’s who gave his mentor full credit for the formula.]

Pearson was a product of his times. Darwin’s ideas about the fundamental principles that guide evolution; namely heredity, variation, and natural selection, influenced the thinking of many scholars. Galton had introduced the term eugenics and started the eugenics movement, which was dedicated to improving the human race through selective breeding. This was a period of time when many scientists believed nature (heredity) to be far more important than nurture (environment) in determining personal qualities. Indeed, Pearson developed formulas for correlation coefficients appropriate for noncontinuous measures in his attempt to show that “… the degree of resemblance of the physical and mental characteristics in children is one and the same” (Pearson, 1903, p. 203). Pearson became a strong advocate for eugenical action. Pearson could be quite accurately described as a Social Darwinist, an imperialist, nationalist, and a racist (Gresskurth, 1980). For instance, he believed that war was necessary to eliminate “inferior stock.” He also opposed legislation to aid the oppressed. According to Pearson, “No degenerate and feeble stock will ever be converted into healthy and sound stock by the accumulated effects of education, good laws, and sanitary surroundings” (Semmel, 1958). Unfortunately, his nationalistic and racist beliefs even influenced his scientific conclusions (e.g., Delzell & Poliak, 2013). Several of his research projects serve as an example of how personal bias and preconceived notions can influence the methods used and even the conclusions drawn from scientific investigations (see Box 2.3).

The eugenics movement was birthed in England, came-of-age in the United States (where forced sterilization, marriage restrictions, and eugenical segregation policies were legalized to varying degrees across the country), and was adopted as national policy in Nazi Germany (e.g., Kühl, 1994). The death of millions of physically, mentally, racially, and socially “inferior” people was the result.

Pearson died in 1936, just before the outbreak of World War II. Moving forward we must take only the best of Karl Pearson; namely, his insistence on the importance of quantifying social phenomena and the numerous correlational techniques he developed to achieve this goal. Additionally, we can recognize that his vision to accomplish a paradigm shift in the social sciences has led to many innovative, multivariate methods that bridge the gap between experimental and correlational designs.

Find this and other spotlights on important statisticians in the Nesselroade & Grimm textbook.

Delzell, D. A. P., & Poliak, C. D. (2013). Karl Pearson and Eugenics: Personal opinions and scientific rigor. *Science and Engineering Ethics*, *19*, 1057-1070.

Grosskurth, P. (1980). *Havelock Ellis: A Biography.* New York: Knopf.

Kühl, S. (1994). *The Nazi Connection: Eugenics, American racism, and German national socialism*. New York: Oxford University Press.

Pearson, K. (1903). On the inheritance of the mental and moral characters in man, and its comparison with the inheritance of the physical characters. *Journal of the Anthropological Institute*, *33*, 179–237.

Semmel, B. (1958). Karl Pearson: Socialist and Darwinist. *British Journal of Sociology*, *9*(2), 111–125.

Stouffer, S. A. (1958). Karl Pearson―An appreciation on the l00th Anniversary of his birth. *Journal of the American Statistical Association* 53, pp. 23–27.

Walker, H. M. (1968). Pearson, K. In D. L. Sills (Ed.), *International Encyclopedia of the Social Sciences*, Vol. II (pp. 496-503), New York: Macmillan and The Free Press.

Yule, G. U. (1895). On the correlation of total pauperism with proportion of out-relief. I. All ages. *Economic Journal*, *5*, 603–611.