Rating: 
Summary: Excellent, but not for everyone
Review: After I bought this book, I found myself talking about it a lot; my friends asked me whether they should buy it. My answer was "well, it's complicated."The g Factor is a giant monolith of scientific information in the field of psychometrics. The concepts are abstruse, the language dense, and the print small. The entire book is over 600 pages and written as though the typical reader has a BA in statistics and a Masters in Psychology (which in retrospect is probably true). I'm dedicated enough to wade through The g Factor, and boy it is a veritable gold mine of information, but reading the thing really does feel like mining for gold. For the less dedicated reader, reading this outline might be preferable to reading the book. 1. Charles Spearman did research and discovered that mental ability in any area consists of (g) + (a) + (b), where g is the general factor, a is a sub factor, and b a specific factor. (Kindof like your ability to throw a fastball consists of your general athletic ability, plus your throwing ability, plus your skill and familiarity with pitching baseballs.) Spearman found out that in the mental arena, g accounts for the majority of the variance, which is surprising, but basicly means that intelligence is really important. 2. People invented IQ tests to try to gague g, but there were always problems and arguments about the testing. After 100 years, the tests were improved and the arguments were answered. Modern tests, like the Wechsler, correlate at around 70% with g. Raven's Progressive Matrices, a nonverbal test involving pattern recognition, correlates around 80% with g (but doesn't tap verbal factors). 3. Based on jillions of studies of twins reared apart, g turns out to be about 85% heritable by adulthood. The environment you grew up in does almost nothing to affect your g, although children are malleable and experience *temporary* boosts or gains depending on the environment they are currently surrounded by. Genes for high-g are almost all dominant, as demonstrated by inbreeding depression (inbred children are about 6 IQ lower than expected) and heterosis (1st generation mixed-race children are about 4 IQ points higher than expected). 4. Because of #3, despite huge piles (literally billions of dollars) of tax money thrown at increasing intelligence, it all came to nothing. 5. The g factor correlates with a number of biological factors like height, myopia, lightness of hair and eyes, and an inability to tatse phenylthiocarbamide (please don't ask me to tell you what that means; I don't even know how it tastes). It's is linked to a sense of humor, creativity, memory, supermarket shopping, and talking speed. This g factor is also inversely related to criminality, welfare dependency, social conservatism, dogmatism, impulsivity, truancy, smoking, untruthfulness, and obesity. 6. IQ scores have been rising at a rate of around 3 points per decate for the past 80 years; this is called the Flynn effect. This has been going on because of schooling and television, improved nutrition (recall that heights have been increasing over the last century), test design, and heterostasis. Some of the IQ gains are therefore "hollow," or non-g related, representing no real increase to intelligence, but some are meaningful, which means that we are perhaps 10 "real" IQ points smarter than we were 100 years ago. 7. Blacks aren't as intelligent as whites on the average. Yes, really. Their IQ in the US is about 18 points lower than that of whites (most people report a mere 15 or even 10 point difference, but Jensen goes for the full blown 18 point difference, which is probably most honest but also most depressing). They also have a smaller Standard Deviation, meaning that there's a bit less variation in their intelligence. Aggregated data from all kinds of studies, most recently with MRI, show that black people have brains which are smaller by around 80 cubic centimeters, and the resulting IQ disparity isn't test bias or anything else; it's all g. In fact, once brain size is controlled for, racial disparities in g vanish. 8. The "default hypothesis" for #7 is that it's genetic. Environmentalist arguments are able to account for some 20-30% of the gap by talking about nutrition, socialization, low rates of breast feeding, and discrimination, but the rest is pretty clearly the result of heredity, and you can tell because brain size is correlated with g at around 60%, and of course because of #4. 9. Men and women are of equal intelligence. Numerous studies and analysis show no measurable difference in their g (although black women are smarter than black men by some 3 points). Men are better at visuospatial and mathematical tasks, while women are better verbally and with short term memory. Put simply, if these topics fascinate you and you would like more specific information, then The g Factor is well worth the price tag! But if not, you'll be happier with The Bell Curve or The Blank Slate.
Rating:
Summary: Best book in differential psychology in the 1990s
Review: Currently, it stands as the most comprehensive tome on g ever written. More than that though, it is a masterwork in the field of intelligence and individual differences. If Jensen's place as one of the premier scientists in the field of psychology wasn't already firmly entrenched, this work definitely put him there.
Rating:
Summary: True Scholarship. Destined to be Classic of Science.
Review: Dr. Jensen's book is a work of true scholarship, research and analysis. Many "writers" write, comment, or critique the area of human intelligence, but very few are true scholars and researchers. True scholars collect data, collect data in the field, and conduct real population studies. True scholarship begins with data gathering. Dr. Jensen has collected data from school children across America. They have been published in Professional journals. Dr. Jensen is interested in the Truth, not wishful thinking. This book is not easy read. I had to go over some chapters several times. Moreover, I have read his earlier works. "Bias in Mental Testing". Dr. Jensen is a meticulous, reasoned scholar. It not the cafe-intellectual "pinhead" who argues from emotions only. Great Book. Dr. Jensen goes into great technical details about the G factor, General intelligence, in this book. It's hard to summarize it all, should buy book and read all details.. This book and issues raised will not go away. Intelligence is foundation of Tech and Computer economy. Must Buy. Variation in intelligence exists in goups and in individuals just as there are short and tall people. Anyway, this is a work of scholarship based on 40 years of research and analysis. Destined to be classic. All scholars must contend with this book if they are serious researchers.
The great adage applies: "You shall know the Truth, and the Truth will set you Free."
Rating:
Summary: True Scholarship. Destined to be Classic of Science.
Review: Dr. Jensen's book is a work of true scholarship, research and analysis. Many "writers" write, comment, or critique the area of human intelligence, but very few are true scholars and researchers. True scholars collect data, collect data in the field, and conduct real population studies. True scholarship begins with data gathering. Dr. Jensen has collected data from school children across America. They have been published in Professional journals. Dr. Jensen is interested in the Truth, not wishful thinking. This book is not easy read. I had to go over some chapters several times. Moreover, I have read his earlier works. "Bias in Mental Testing". Dr. Jensen is a meticulous, reasoned scholar. It not the cafe-intellectual "pinhead" who argues from emotions only. Great Book. Dr. Jensen goes into great technical details about the G factor, General intelligence, in this book. It's hard to summarize it all, should buy book and read all details.. This book and issues raised will not go away. Intelligence is foundation of Tech and Computer economy. Must Buy. Variation in intelligence exists in goups and in individuals just as there are short and tall people. Anyway, this is a work of scholarship based on 40 years of research and analysis. Destined to be classic. All scholars must contend with this book if they are serious researchers.
The great adage applies: "You shall know the Truth, and the Truth will set you Free."
Rating:
Summary: Great book for the non-technical reader
Review: First, I am not a professional psychologist nor do I plan to become one. My BS is in Psychology and I have done Cognitive and Neuroscience research. This is a demanding book if you are not versed the field of psychometrics. Jensen cannot avoid having to present some of this information in a technical manner. He does, however, present the technical details of the subject in the clearest possible way. In fact this book has done much to strengthen my intrest in statistics. The g-factor would be great reading for someone who has read some of the more popular books about human intelligence(Bell Curve, Mismeasure of Man, etc..) and is looking for a broader perspective on these issues. The highly controvesial subjects (race, environment vs. heredity, education) only account for a few parts of the book. Many of the other subjects(like world IQ increases, biological correlates, the history of g, and the politicizing of IQ) are equally facinating. Perhaps the greatest aspect of the book is Jensen's perspective on this subject. Many of his views are as fresh and creative as they are comprehensive.
Rating:
Summary: It will make a man out of you
Review: George Bernard Shaw said that reading Das Capital by Karl Marx, "would make a man out of you." Actually, Marx's pie-in-the-sky egalitarianism is more the stuff of teenagers than of men. Jensen's G Factor, on the other hand, is about as sophisticated as social science gets, and he pulls no punches. So be ready to venture out from PC's reassuring bosom into the cold world of reality...and bring your statistics textbook with you for help.
Rating: 
Summary: An excellent book that could've been composed better.
Review: I found the "The G Factor:...' to be enlightening and thoroughly researched book on a fascinating topic. Although the basic premise, that intellignece matters and that it is primarily inherited was evident, the book was rarely boring. The basic premise regarding intelligence was broadened by Jensen to explain intellignece, G, in statistical and physical terms with forays into G's manifestations in life. The book will not appeal to people without a strong interest in statistics; it will not appeal to people who believe that the environment is the primary shaper of our personailties. I have two criticisms of the book. The book could have been omposed better; sentences were sometimes very long with excessive flourish. My second criticism concerns the authors purpose. Although I have no doubt as to the validity of the information presented, I would wonder about the emphasis of black and white racial differences... I would have liked to see more racial balance in the examination of racial differences. Overall, I found the book to be a fascinating and enlightening.
Rating:
Summary: ...., but could have been written better.
Review: I found the "The G Factor:...' to be enlightening and thoroughly researched book on a fascinating topic. Although the basic premise, that intellignece matters and that it is primarily inherited was evident, the book was rarely boring. The basic premise regarding intelligence was broadened by Jensen to explain intellignece, G, in statistical and physical terms with forays into G's manifestations in life. The book will not appeal to people without a strong interest in statistics; it will not appeal to people who believe that the environment is the primary shaper of our personailties. I have two criticisms of the book. The book could have been omposed better; sentences were sometimes very long with excessive flourish. My second criticism concerns the authors purpose. Although I have no doubt as to the validity of the information presented, I would wonder about the emphasis of black and white racial differences... I would have liked to see more racial balance in the examination of racial differences. Overall, I found the book to be a fascinating and enlightening.
Rating:
Summary: What a scholar! Profound thesis, fascinating trivia
Review: Jensen's definitions and descriptions of his science are fascinating. g stands for General Ability. It is neither IQ nor intelligence itself. Intelligence, per Jensen, is the capacity of all animals to perceive and act upon the natural world. The Intelligence Quotient is a statistical artifice that maps individuals' problem solving abilities into a linear scale according to a Gaussian bell-curve distribution. By definition the average IQ is 100 and the standard deviation (SD) 15. By the properties of the bell curve approximately 2/3 of the population falls within one SD of the median, that is, between 85 and 115. However, as Jensen points out repeatedly, general ability is not a linear function. The discriminators are whether or not an individual can solve specific problems. There is no way to define a lineal relationship between two individuals if once can figure out (for instance) the lowest primo number greater than 90 and another cannot, or one can figure that context requires the word above to be "prime" not "primo" and another cannot. There is no metric for "g" itself. Rather, all tests of mental ability have a degree of "g loading." Psychometrics is the science of assessing and manipulating information about a quality that cannot be measured directly. Jensen devotes much energy to defending the validity of "g", this thing that defies direct measurement. It is real because:
a) It is statistically "there." It is highly correlated among myriad tests.
b) It works in the real world. There is no single discriminator that approaches the value of "g", usually proxied by an IQ test score, as a predictor of educational or job performance.
c) It has equal predictive power for both sexes, all ages and all populations of mankind. It is independent (as he takes endless pages to prove) of race, language and socio-economic status (SES).
d) Many seemingly unrelated kinds of tests all turn out to measure the same thing. Tests may be verbal or pictorial, or may simply measure the time it takes to react to and act upon a visual or auditory stimulus.
e) By adulthood it no longer has much to do with advantages such as hearing Mozart in the womb or a Montessori kindergarten, or disadvantages such as Jim Crow and slavery. The other reviews of this book are quite good. Some of Jensen's many fascinating observations:
o Incest is a bad idea. The offspring have a significant intelligence deficit.
o Smart parents, alas, can't count on having equally smart kids. On average their intelligence regresses halfway back to the mean (100 for white Americans). On the bright side, the average people manage by dumb luck to produce enough smarties for each succeeding generation.
o Breast feeding makes a huge difference, about 7 IQ points. Blacks do not breast feed as often or as long as whites. Big, easy change to make in society.
o The factors generally agreed to comprise "g" differ among races and sexes. Blacks exceed whites in short term memory. Men exceed women in spatial intelligence. When the many individual factors are aggregated they reveal different means for different races, with whites in the middle with an average of 100.
o Individuals with IQs below 70 are generally considered to be retarded. White retarded kids frequently look and act somehow different, while retarded kids of other races are more normal in terms of socialization, motor skills and energy. This is related to the two types of retardation, familial and organic. In simple words, there is something "wrong with" an organically retarded child. A bad forceps delivery, spina difida or one of a number of identifiable anomalies. Familial retardation, on the other hand, simply represents a bad spin of the chromosomal wheel of fortune that is sexual reproduction. The odds are higher in populations whose median IQs are lower.
o Cause for concern: If Vanhansen and Lynn are right in "IQ and the Wealth of Nations" there are perhaps a dozen countries in which the average citizen would be considered retarded and hence marginally educable by U.S. standards.
o Illiteracy is not always a matter of reading. Below the threshold of retardation people often have the same inability to understand a sentence whether it is written or spoken. The issue is having enough "g" to make sense out of the words.
o People with lower IQs are markedly more fertile than those with higher IQs. This dysgenic (opposite of eugenic) trend stands to lower "g" within the U.S. population. Average intelligence will of course remain at 100 because by definition it is the population mean. Jensen comes across through this book as first and foremost an inquisitive mind, a scientist. He often states with unashamed candor that he (nor anybody else) knows the answer to some knotty problems of psychometrics, like the Flynn effect that shows overall intelligence rising 3 points per generation. Contrast his thoroughness and openness with the tone of advocacy found in Stephen Jay Gould (Mismeasure of Man) and sites such as fairtest dot org. Steven Pinker describes in "The Blank Slate, the Modern Denial of Human Nature" the extreme and prolonged abuse Jensen has taken from the academic community. I'm happy to report he hasn't lost his sense of balance. Or sense of humor.
Rating:
Summary: As Good As It Gets
Review: Professor Jensen's work on mental abilities, as summarized in this book, examines the different aspects of intelligence in a great deal of detail, including the history of the subject along with the work of early researchers, the different schools of thought, the biological correlates, heritability, environmental factors, the gender and race differences and plausible explanations, the role of intelligence in a person's development and the social implications. The subject of human intelligence had been a controversial one since its conception. To claim that different people have different levels of intelligence runs counter to the cherished notion that all men are created equal. However, empirical evidence is overwhelming that every human being is not born with equal potential. Some people do not like the findings of scientific studies because the findings undermine the premises of their belief, and they tend to attack and discredit the scientist and impugn his motive. Others may not like the findings but accept them if they are satisfied that the findings are the results of scientific methods. This book appeals to the latter group, as the professor was very meticulous in explaining the hypothesis, the experiment, the data, and the analysis. He was very candid about what he was sure and what he was not so sure and why. I learned a lot about the subject of human intelligence from this book. More importantly, as I read this book, I could see that even as the professor pursues the subject with uncommon vigor, he is also a healthy all-around skeptic and would not rest until all arguments, including "rival" ideas, have been thought through. For this reason, I believe what I learned is the best knowledge to date of the subject. If you are seriously interested in the subject of mental abilities, there is frankly no substitute to this book.
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