Sex Linkage of Intelligence: The X-Factor

by Robert Lehrke

Overview

The author presents a theory that major genes controlling the growth of human intelligence, both left- and right-brain attributes, are on the X-chromosome. The more significant of the implications of such X-linkage include

•  Males tend to be more variable in intelligence. It is well known that males are far more likely to have intellectual deficits, including mental subnormality, learning disorders, and behavior problems. This book also presents evidence that males are more likely to be exceptionally high in cognitive abilities (other than memory), and in such areas as advanced mathematics, spatial perception, and creative music.

•  Partial or total reversions to the aboriginal level of intelligence can account for virtually all cases of non-specific mental subnormality. These conditions are now identified by such terms as Renpenning syndrome, Martin-Bell syndrome, Fragile-X syndrome, and cultural-familial mental retardation. Because of the probability of offsetting genes, females are less likely to be severely affected by these conditions.


•  Since the X-linked genes control a pattern of growth, boys are more variable in the age of readiness for the skills required for progress in school. Some are precocious, but many are delayed, and not ready for the three R's at the traditional age of 6. This is the basis for almost all cases of learning disability.

•  Being on the X-chromosome, these genes, favorable or unfavorable, are not passed on from father to son, although they are passed on from father to daughter. This invalidates earlier studies of parent-child transmission of IQ, which have included father-son correlations. In effect, earlier studies have come up with estimates of the heritability of intelligence that are too low.

Product Details

ISBN-13:	9780275959036
Publisher:	Bloomsbury Academic
Publication date:	11/30/1997
Series:	Human Evolution, Behavior, and Intelligence
Pages:	208
Product dimensions:	6.00(w) x 9.00(h) x 0.62(d)
Lexile:	1390L (what's this?)

About the Author

ROBERT LEHRKE, now retired, worked as a clinical psychologist in Minnesota state institutions and in private practice and has taught at several colleges and universities, including William and Mary. Dr. Lehrke has published extensively in the area of sex-linked intelligence.

Table of Contents

Preface
Background
The Big Leap
In Other Words
Chromosomes, Especially X
Mutations
Neoteny
Variability in Intelligence
Division of Labor Within the Brain
Natural and Sexual Selection
The Races and the Spread of Homo Sapiens
Other X-Linked Traits
X-Linked Mental Deficiency
X-Linkage and Learning Disorders
Inheritance of X-Linked Traits
Sex Differences in Variance
Editorial Comment: What Good Is All This?
Glossary
References
Index

Editorial Reviews

Lehrke, a retired clinical psychologist, theorizes that the genes controlling the growth pattern of major intellectual traits are located on the X-chromosome; and that higher human intelligence arose out of a mutation or series of mutations on the X-chromosome. He discusses basic genetic, neurophysiological, and evolutionary background, as well as variability in intelligence, X-linked mental deficiency, X- linkage and learning disorders, inheritance of X-linked traits, and sex differences in variance. Annotation c. by Book News, Inc., Portland, Or.

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