|Definition of Theory |
the-o.ry (the'a re, thir'e) n., pi. -riea [< Fr. or LL.: Fr.
theorie < LL. theoria < Gr. theoria, a looking at, contem-
plation, speculation, theory < theorem: see THEOREM] 1.
orig., a mental viewing; contemplation 2. a speculative
idea or plan as to how something might be done 3. a
systematic statement of principles involved /the theory
of equations in mathematics/ 4. a formulation of apparent
relationships or underlying principles of certain observed
phenomena which has been verified to some degree 5.
that branch of an art or science consisting in a knowledge
of its principles and methods rather than in its practice;
pure, as opposed to applied, science, etc.
"Race, Evolution, and Behavior: A Life History Perspective", J. Philippe Rushton
Regression to the Average
Regression to the Average provides still another way to test if race differences are genetic. The children of very tall parents are taller than average. But they are shorter than their parents and nearer the average of their race. Similarly, children of very short parents are shorter than average, but taller than their parents. This is called the Law of Regression to the Average. It is not true just for height, but for IQ as well. Most physical and psychological traits show some regression effect.
Regression to the Average happens when very tall (or very high IQ) people mate because they pass on some, but not all, of their exceptional genes to their offspring. The same thing happens with very short (or very low IQ) people. It's like rolling a pair of dice and having them come up two sixes or two ones. The odds are that on the next roll, you'll get some value that is not as high (or as low).
Here's why regression is important to our studies. Because Whites and Blacks come from different races, they have many different genes. The Law of Regression predicts that for any trait, scores will return to the average of their race. The Regression Law predicts that in the U.S., Black children with parents ofIQ115 will regress toward the Black average of 85, while White children with parents of IQ 115 will regress only toward the White average of 100.
The law also works at the other end of the scale. Black children with parents of IQ 7Q will move up toward the Black average IQ of 85, but White children with parents of IQ 70 will move further up toward the White average of 100. When we test these predictions about Regression to the Average from parent to child they prove true.
The Regression Law also works for brothers and sisters. Black and White children matched for IQs of 120 have siblings who show different amounts of regression. Black siblings regress toward an IQ of 85, while White siblings regress only to 100. The opposite happens at the lower end of the scale. Black and White children matched for IQs of 70 have siblings who regress differently. Black siblings regress toward an average of 85, whereas White siblings move to 100.
Regression to the Average explains another interesting finding. Black children born to rich parents have IQs that are two to four points lower than do White children bom to poor parents. The high IQ Black parents were not able to pass on their IQ advantage to their children even though they did give them good nutrition, good medical care, and good schools. Only genes plus environment tell the whole story.