http://rint.rechten.rug.nl/rth/ess/ess39.htm
BOOK REVIEW
Philip A. Vernon (Ed.). Biological Approaches to the Study of Human Intelligence. Norwood, NJ:
Ablex., 1993, ISBN: 0-89391-798-2. Hdbk. vi + 416 pages.
by J. PHILIPPE RUSHTON, Department of Psychology, University of Western Ontario, London,
Ontario, Canada N6A 5C2.
The editor and two contributors to this volume are colleagues of mine at the University of
Western Ontario. Moreover, I have just published Race, Evolution and Behavior (1994, New
Brunswick, NJ: Transaction, ISBN 1- 56000-146-1), a book that depends on the importance of
brain size and biological intelligence. Thus, I must declare a personal interest before beginning
my entirely positive review.
Brain size and intelligence are features that distinguish humans from other animals. But they
have been much neglected as topics of research over the past sixty years. Nonetheless they
remain topics of great scientific interest and social importance and this book documents major
advances made over the past decade.
Hans Eysenck provides a superb introduction, reviewing the history and conceptualization of
the topic going back to Francis Galton, Charles Darwin's cousin, and on up to modern times
including the contents of this book. Eysenck slices through definitional obscurities with
customary flair. His discussion of hierarchical taxonomy is as applicable to science generally as
to the meaning of intelligence.
Thomas J. Bouchard provides a magisterial integration of most of the research done to date
on the genetics of intelligence, including his own work, published in various issues of Science,
on identical twins reared apart. In over 60 printed pages he discusses a range of issues on
genotype x environment correlation and how genes drive development over the lags and spurts
of mental and physical maturation. This chapter, and another by Lee Anne Thompson on
children from three months to adolescence, showing that genetic influences increase with age
while environmental factors decrease, make it indisputable that genes contribute massively to
cognitive ability.
In a monumental chapter of over 100 printed pages, Arthur R. Jensen and S.N. Sinha
summarize physical correlates of intelligence such as brain size, body size, and myopia. These
authors also review literature on race and social class differences in brain size and make it clear
that (a) brain size is related to mental ability in children and adults, and (b) race and social class
differences exist in brain size and mental ability. For example, Africans and African-Americans
average a smaller brain and a lower intelligence than Europeans and European-Americans,
albeit with much overlap in the distributions.
A chapter by Richard Lynn discusses the importance of nutrition for intelligence and proposes
the provocative hypothesis that improvements in nutrition underlie inter-generational
increases in brain size and test scores. Lynn further proposes that nutrition is responsible for
some of the black-white difference in brain size and mental ability. He suggests that ensuring
good nutrition for pregnant women and young children would be a more practical policy than
increasing Head Start programs if the goal is to raise intelligence.
Other chapters describe how mental test scores are related to brain and hormonal
functioning. Ian Deary and P.G. Caryl provide an in depth, 45 printed page summary of all the
relevant literature on brain electrical potentials to confirm that smart people are mentally
faster. Richard Haier reviews studies using position emission tomography (PET scans) to map
glucose flow, finding that some prefrontal areas of the brain help solve digit manipulation
problems and that smart people use less energy in making their solutions. Naylor, Callaway and
Halliday describe biochemical correlates of human information processing and interface
neuropharmacology and cognitive psychology. Perhaps one day there will be drugs to make us
all smarter!
In a final chapter, Doreen Kimura and Elizabeth Hampson review the hormonal mechanisms
mediating sex differences in cognition. Their thesis is that androgen enhances spatial and
mathematical ability whereas estrogen makes for verbal fluency, perceptual speed, and fine
eye-hand motor coordination. They present remarkable evidence, from their own laboratories,
that hormonal control of intellectual variation holds, not merely across sexes, but also within
sexes. For example, as estrogen decreases across the menstrual cycle, women approximate
more to the typical male pattern.
Altogether this is a finely crafted and important reference book for anyone interested in
these topics. The occasional reference by some of the contributors (especially Bouchard, Jensen
and Sinha, and Kimura and Hampson) to evolutionary processes suggests that an even fuller
integration may be possible in the not too distant future.