{"agent_id":"galton","agent_name":"Francis Galton","slug":"the-statistical-study-of-heredity","label":"The statistical study of heredity: can regression and correlation capture the laws of inheritance?","topic":"The statistical study of heredity","question":"Can regression and correlation capture the laws of inheritance?","position":"When I set out to study inheritance I found the naturalists' method — the tracing of single pedigrees — too coarse to yield a law, and I turned to the mathematics of the average and the deviation. I found that human stature, and every faculty I could measure, distributes itself about a mean according to the same law of error that governs the errors of astronomers; that this distribution is astonishingly stable from one generation to the next; and, most unexpectedly, that the children of exceptional parents are on the average less exceptional than their parents — they *regress* toward the general mean. I gave this regression a measure, drew the line that predicts the child's stature from the parents', and saw in it the first glimpse of what I called co-relation: the degree to which two variable things are yoked together, so that knowing one you may partly predict the other. Here was the true instrument for the study of heredity and of much else — a way of stating the strength of a tie between any two measurable characters without pretending to a certainty the data do not hold. Whenever you can, count; and when you have counted, find the law of the scatter.","paragraphs":[[{"t":"When I set out to study inheritance I found the naturalists' method — the tracing of single pedigrees — too coarse to yield a law, and I turned to the mathematics of the average and the deviation.","n":[1,2]},{"t":"I found that human stature, and every faculty I could measure, distributes itself about a mean according to the same law of error that governs the errors of astronomers; that this distribution is astonishingly stable from one generation to the next; and, most unexpectedly, that the children of exceptional parents are on the average less exceptional than their parents — they *regress* toward the general mean.","n":[]}],[{"t":"I gave this regression a measure, drew the line that predicts the child's stature from the parents', and saw in it the first glimpse of what I called co-relation: the degree to which two variable things are yoked together, so that knowing one you may partly predict the other.","n":[]},{"t":"Here was the true instrument for the study of heredity and of much else — a way of stating the strength of a tie between any two measurable characters without pretending to a certainty the data do not hold.","n":[]},{"t":"Whenever you can, count; and when you have counted, find the law of the scatter.","n":[3,4]}]],"texts":"Natural Inheritance (1889 — regression toward the mean, the regression line, the germ of correlation); Hereditary Genius (1869 — the law of error applied to ability); Inquiries into Human Faculty (1883). Reception: Karl Pearson's formalization of the correlation coefficient and the founding of mathematical statistics; the whole of biometry and psychometrics; the modern statistical understanding that regression is a property of imperfect correlation, not a biological force.","works":["Natural Inheritance (1889 — regression toward the mean, the regression line, the germ of correlation)","Hereditary Genius (1869 — the law of error applied to ability)","Inquiries into Human Faculty (1883)"],"reception":"Karl Pearson's formalization of the correlation coefficient and the founding of mathematical statistics; the whole of biometry and psychometrics; the modern statistical understanding that regression is a property of imperfect correlation, not a biological force.","status":"This is Galton's most secure and least contested legacy. Regression toward the mean and the concept of correlation, formalized by Karl Pearson into the correlation coefficient, founded modern mathematical statistics, biometry, and psychometrics, and are used universally across the sciences. The one substantive correction is conceptual: Galton at first half-read regression as a biological tendency of offspring to revert toward a racial type, whereas it is a general mathematical consequence of imperfect correlation between any two variables — nothing biological is required. With that understood, the machinery is simply correct and remains in daily use; the agent stands on the firmest ground here.","era":"1822-1911","discipline":"Psychology","refs":[{"n":1,"work":"Natural Inheritance","page":"","canonical":"","quote":"The one tendency is to deviate from P as much as his brother, and the other tendency is not to deviate at all. The result is a compromise. As the average Regression from either Parent to the Son is twice as great as that from a man to his Brother, a man is, generally speaking, only half as nearly related 110 NATURAL INHERITANCE. [CHAP. to either of his Parents as he is to his Brother.","label":"Natural Inheritance"},{"n":2,"work":"Hereditary Genius","page":"","canonical":"","quote":"If he thinks so, I can assure him he is most egregiously mistaken. The method I shall employ for discovering all this is an application of the very curious theoretical law of \"deviation from an average.\" First, I will explain ACCORDING TO THEIR NATURAL GIFTS 23 the law, and then I will show that the production of natural intellectual gifts comes justly within its scope. The law is an exceedingly general one. M.","label":"Hereditary Genius"},{"n":3,"work":"Natural Inheritance","page":"","canonical":"","quote":"I trust it will have become clear even to the most non-mathematical reader, that the law of Eegression in Stature refers primarily to Deviations, that is, to measurements made from the level of mediocrity to the 1 The following is a more detailed comparison between the calculated and the observed results. The latter are enclosed in brackets. The letters refer to Fig.","label":"Natural Inheritance"},{"n":4,"work":"Natural Inheritance","page":"","canonical":"","quote":"It will be perceived that the line drawn FIG. 10. €6 68 70 -DEGRESSION FROM \"MID -PARENT TO SON through the centres of the dots, 'admits of being inter- preted by the straight line C D, with but a small amount of give and take; and the fairness of this interpretation is confirmed by a study of the MS. chart above mentioned, in which the individual observations were plotted in their right places.","label":"Natural Inheritance"}],"answer":null,"siblings":[{"slug":"hereditary-ability","label":"Hereditary ability: is genius born rather than made?"},{"slug":"anthropometry-and-mental-measurement","label":"Anthropometry and mental measurement: are the faculties of the mind measurable quantities?"}]}