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Christopher D. Green
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Francis Galton (1869)
Robert H. Wozniak
© 1999 Robert H. Wozniak. All rights reserved. Previously published in Wozniak, R. H. (1999). Classics in Psychology, 1855-1914: Historical Essays. Bristol, UK: Thoemmes Press. Reprinted by permission of the author.
[Classics Editor's note: This is not an introduction to the 1865 article, "Hereditary Talent and Character," but to the book-length treatment of the same topic that Galton published four years later, Hereditary Genius.]
Around the middle of the 19th century, two publications of great importance provided Francis Galton with the motivation to pursue a line of research that led to the appearance of his most famous book, Hereditary Genius: An Inquiry into Its Laws and Consequences. The first of these was Downes' translation of Adolphe Quetelet's Letters on the Theory of Probabilities. From Quetelet, Galton learned of the Laplace-Gauss distribution or, as it is often called, the "normal curve of variation from an average" and of the fact (at least as claimed by Quetelet) that physical characteristics of human beings such as height and chest size are normally distributed.
The second was Charles Darwin's On the Origin of Species. Darwin's claim that evolution takes place through natural selection operating on variation in characteristics influencing the probability of survival (and hence procreation) led to Galton's developing a passionate interest in human variability. While this interest extended to human variation in all of its forms, Galton was particularly intrigued by individual differences in mental traits and most especially by variation in mental ability or, as he called it, "genius".
In the 1860s Galton set out to examine the extent to which genius is hereditary. This research led in 1869 to the publication of Hereditary Genius, the aim of which was "to show...that a man's natural abilities are derived by inheritance, under exactly the same limitations as are the form and physical features of the whole organic world."
In pursuing this analysis, Galton's first problem was to develop a method for assessing high levels of mental ability. The approach that he took was to assume that mental ability is closely correlated with eminence (reputation) in a given profession. As he described it, "I feel convinced that no man can achieve a very high reputation without being gifted with very high abilities; and...few who possess these very high abilities can fail in achieving eminence."
Galton then attempted to marshal evidence in favor of the proposition that mental ability is inherited. First he examined the shape of the distribution of mental ability. Analyzing the scores of 200 candidates who had taken the Mathematical Tripos at Cambridge as well as those that had been obtained by 72 candidates for civil service positions, Galton showed that these scores (and hence presumably the psychological characteristics underlying the scores) were distributed in much the same way as inheritable physical traits, that is to say, normally.
While this similarity in the shape of the distribution of mental and physical characteristics did not in itself imply the inheritability of mental traits, it was consistent with Galton's claim. More importantly, it also allowed him to estimate the percentages of men that would be expected at each of a series of "levels" of mental ability ranging from the highest to the lowest. This, in turn, provided a standard against which the hypothesis of inheritability of mental ability could be evaluated.
The evaluation of this hypothesis was at the heart of Hereditary Genius and the results of this analysis provided Galton with his best evidence for the claim that mental abilities are inherited. Since he had no way of measuring inheritability directly, Galton decided to focus on the family backgrounds of those at the highest levels of eminence and assess the extent to which eminence appeared to run within their families. In successive chapters of Hereditary Genius, he presented these data for judges, statesmen, the aristocracy, commanders, literary men, men of science, poets, musicians, painters, divines, and academics among others.
Measuring the frequencies with which eminence was to be found among first (fathers, brothers, sons), second (grandfathers, grandsons, uncles, nephews), and third degree relations (great-grandfathers, great-grandsons, great-uncles, great-nephews, first cousins) of members of the target sample, Galton compared these frequencies to those that would be expected from the frequency of eminence within the general population. Finding the relations of eminent men to exhibit a much greater frequency of eminence than expected on this basis and noting that the frequency of eminence declined from first to second to third degree relations, Galton concluded that it could only be because mental ability runs in families.
For the period this was an extremely provocative conclusion. More importantly, however, it was a conclusion bolstered by data and statistical analysis (especially the comparison of an obtained sample distribution to that expected on the basis of known population characteristics). In this regard it was ground-breaking. As Galton himself described it: "The theory of hereditary genius...has been advocated by a few writers in past as in modern times. But I may claim to be the first to treat the subject in a statistical manner, to arrive at numerical results, and to introduce the 'law of deviation from an average' into discussions of heredity." The publication of Hereditary Genius thus marked the birth of quantitative differential psychology.
 1822-1911. For biographical information on Galton, see Galton, F. (1908). Memories of My Life. London: Methuen; Pearson, K. (1914-30). The Life, Letters and Labours of Francis Galton (3 vols. in 4). Cambridge: At the University Press; Forrest, D. W. (1974). Francis Galton: The Life and Work of a Victorian Genius. New York: Taplinger; and Fancher, R. E. (1979). Pioneers of Psychology (Chapter 7: The measurement of mind: Francis Galton and the psychology of individual differences). New York: Norton, pp. 250-94.
 Quetelet, A. (1849). Letters Addressed to H.R.H. the Grand Duke of Saxe Coburg and Gotha, on the Theory of Probabilities, as Applied to the Moral and Political Sciences. London: Layton.
 Darwin, C. (1859). On the Origin of Species by Means of Natural Selection, or, The Preservation of Favoured Races in the Struggle for Life. London: John Murray.
 Galton, F. (1869). Hereditary Genius: An Inquiry into Its Laws and Consequences. London: Macmillan, p. 1 (Reprinted, Bristol: Thoemmes Press, 1999).
 Ibid., p. 49.
 Ibid., p. vi.