The Bell Curve: Intelligence and Class Structure in American Life Read Free

collaboration. Our partnership has led to a more compelling intellectual adventure and a deeper friendship than we could have imagined. Authorship is alphabetical; the work was symbiotic.
    At last, how shall we express our thanks to Susan Herrnstein and Catherine Cox? They could not be, and were not, overjoyed to see their husbands embark on a project as controversial as this one. But they have endured our preoccupation with the book and its intrusion into our families’ lives with love and humor. Beyond that, each of them read the entire manuscript, persuasively but affectionately pressing on us the benefit of their fine judgment, their good sense, and their honesty. In more ways than one, this book could not have been written without their help.
    Richard J. Herrnstein
Charles Murray
3 June 1994
    THE BELL CURVE

Introduction
     
    That the word
intelligence
describes something real and that it varies from person to person is as universal and ancient as any understanding about the state of being human. Literate cultures everywhere and throughout history have had words for saying that some people are smarter than others. Given the survival value of intelligence, the concept must be still older than that. Gossip about who in the tribe is cleverest has probably been a topic of conversation around the fire since fires, and conversation, were invented.
    Yet for the last thirty years, the concept of intelligence has been a pariah in the world of ideas. The attempt to measure it with tests has been variously dismissed as an artifact of racism, political reaction, statistical bungling, and scholarly fraud. Many of you have reached this page assuming that these accusations are proved. In such a context comes this book, blithely proceeding on the assumption that intelligence is a reasonably well-understood construct, measured with accuracy and fairness by any number of standardized mental tests. The rest of this book can be better followed if you first understand why we can hold such apparently heterodox views, and for this it is necessary to know something about the story of measured intelligence.
INTELLIGENCE ASCENDANT
     
    Variation in intelligence became the subject of productive scientific study in the last half of the nineteenth century, stimulated, like so many other intellectual developments of that era, by Charles Darwin’s theory of evolution. Darwin had asserted that the transmission of inherited intelligence was a key step in human evolution, driving our simian ancestors apart from the other apes. Sir Francis Galton, Darwin’s young cousin and already a celebrated geographer in his own right, seized on this idea and set out to demonstrate its continuing relevance by using the great families of Britain as a primary source of data. He presented evidence that intellectual capacity of various sorts ran in families in
Hereditary Genius,
published just a decade after the appearance of
Origin of Species
in 1859. So began a long and deeply controversial association between intelligence and heredity that remains with us today. 1
    Galton realized that he needed a precise, quantitative measure of the mental qualities he was trying to analyze, and thus he was led to put in formal terms what most people had always taken for granted: People vary in their intellectual abilities and the differences matter, to them personally and to society. 2 Not only are some people smarter than others, said Galton, but each person’s pattern of intellectual abilities is unique. People differ in their talents, their intellectual strengths and weaknesses, their preferred forms of imagery, their mental vigor.
    Working from these observations, Galton tried to devise an intelligence test as we understand the term today: a set of items probing intellectual capacities that could be graded objectively. Galton had the idea that intelligence would surface in the form of sensitivity of perceptions, so he constructed tests that relied on measures of acuity of