Crime - Cognitive Classes and Social Behavior - The Bell Curve: Intelligence and Class Structure in American Life - Richard J. Herrnstein, Charles Murray

The Bell Curve: Intelligence and Class Structure in American Life - Richard J. Herrnstein, Charles Murray (1996)

Part II. Cognitive Classes and Social Behavior

Chapter 11. Crime

Among the most firmly established facts about criminal offenders is that their distribution of IQ scores differs from that of the population at large. Taking the scientific literature as a whole, criminal offenders have average IQs of about 92, eight points below the mean. More serious or chronic offenders generally have lower scores than more casual offenders. The relationship of IQ to criminality is especially pronounced in the small fraction of the population, primarily young men, who constitute the chronic criminals that account for a disproportionate amount of crime. Offenders who have been caught do not score much lower, if at all, than those who are getting away with their crimes. Holding socioeconomic status constant does little to explain away the relationship between crime and cognitive ability.

High intelligence also provides some protection against lapsing into criminality for people who otherwise are at risk. Those who have grown up in turbulent homes, have parents who were themselves criminal, or who have exhibited the childhood traits that presage crime are less likely to become criminals as adults if they have high IQ.

These findings from an extensive research literature are supported by the evidence from white males in the . Low IQ was a risk factor for criminal behavior, whether criminality was measured by incarceration or by self-acknowledged crimes. The socioeconomic background of the NLSY’s white males was a negligible risk factor once their cognitive ability was taken into account.

Crime can tear a free society apart, because free societies depend so crucially on faith that the other person will behave decently. As crime grows, society must substitute coercion for cooperation. The first casualty is not just freedom but the bonds that make community life attractive. Yes, it is always possible to buy better locks, stay off the streets after dark, regard every stranger suspiciously, post security guards everywhere, but these are poor substitutes for living in a peaceful and safe neighborhood.

Most Americans think that crime has gotten far too high. But in the ruminations about how the nation has reached this state and what might be done, too little attention has been given to one of the best-documented relationships in the study of crime: As a group, criminals are below average in intelligence.

As with so many of the other problems discussed in the previous six chapters, things were not always so bad. Good crime statistics do not go back very far in the United States, but we do not need statistics to remind Americans alive in the 1990s of times when they felt secure walking late at night, alone, even in poor neighborhoods and even in the nation’s largest cities. In the mid-1960s, crime took a conspicuous turn for the worse. The overall picture using the official statistics is shown in the figure below, expressed as multiples of the violent crime rate in 1950.

The figure shows the kind of crime that worries most people most viscerally: violent crime, which consists of robbery, murder, aggravated assault, and rape. From 1950 through 1963, the rate for violent crime was almost flat, followed by an extremely rapid rise from 1964 to 1971, followed by continued increases until the 1980s. The early 1980s saw an interlude in which violent crime decreased noticeably. But the trend-line for 1985-1992 is even steeper than the one for 1963-1980, making it look as if the lull was just that—a brief respite from an increase in violent crime that is now thirty years old.1

The boom in violent crime after the 1950s


Source: Uniform Crime Reports, annual, Federal Bureau of Investigation.

There is still some argument among the experts about whether the numbers in the graph, drawn from the FBI’s Uniform Crime Reports, mean what they seem to mean. But the disagreement has limits. Drawing on sophisticated analyses of these numbers, the consensus conclusions are that victimization studies, based on interviews of crime victims and therefore including crimes not reported to the police, indicate that the increase in the total range of crimes since 1973 has not been as great as the official statistics suggest, but that the increase reflected in the official statistics is also real, capturing changes in crimes that people consider serious enough to warrant reporting to the police.2


The juvenile delinquents in Leonard Bernstein’s West Side Story tell Officer Krupke that they are “depraved on account of we’re deprived,” showing an astute grasp of the poles in criminological theory: the psychological and the sociological.3 Are criminals psychologically distinct? Or are they ordinary people responding to social and economic circumstances?

Theories of criminal behavior were mostly near the sociological pole from the 1950s through the 1970s. Its leading scholars saw criminals as much like the rest of us, except that society earmarks them for a life of criminality. Some of these scholars went further, seeing criminals as free of personal blame, evening up the score with a society that has victimized them. The most radical theorists from the sociological pole argued that the definition of crime was in itself ideological, creating “criminals” of people who were doing nothing more than behaving in ways that the power structure chose to define as deviant. In their more moderate forms, sociological explanations continue to dominate public discourse. Many people take it for granted, for example, that poverty and unemployment cause crime—classic sociological arguments that are distinguished more by their popularity than by evidence.4

Theories nearer the psychological pole were more common earlier in the history of criminology and have lately regained acceptance among experts. Here, the emphasis shifts to the characteristics of the offender rather than to his circumstances. The idea is that criminals are distinctive in psychological (perhaps even biological) ways. They are deficient, depending on the particular theory, in conscience or in self-restraint. They lack normal attachment to the mores of their culture, or they are peculiarly indifferent to the feelings or the good opinion of others. They are overendowed with restless energy or with a hunger for adventure or danger. In a term that was in common use throughout the nineteenth and early twentieth centuries, chronic offenders may be suffering from “moral insanity.”5 In other old-fashioned vocabularies, they have been called inhumane, atavistic, demented, monstrous, or bestial—all words that depict certain individuals as something less than human. In their most extreme form, psychological theories say that some people are born criminal, destined by their biological makeup to offend.

We are at neither of these theoretical poles. Like almost all other students of crime, we expect to find explanations from both sociology and psychology. The reason for calling attention to the contrast between the theories is that public discussion has lagged; it remains more nearly stuck at the sociological pole in public discourse than it is among experts. In this chapter, we are interested in the role that cognitive ability plays in creating criminal offenders. This by no means requires us to deny that sociology, economics, and public policy might play an important part in shaping crime rates. On the contrary, we assume that changes in those domains are likely to interact with personal characteristics.

Among the arguments often made against the claim that criminals are psychologically distinctive, two are arguments in principle rather than in fact. We will comment on these two first, because they do not require any extensive review of the factual evidence.

Argument 1 : Crime rates have changed in recent times more than people’s cognitive ability or personalities could have. We must therefore find the reason for the rising crime rates in people’s changing circumstances.

When crime is changing quickly, it seems hard to blame changing personal characteristics rather than changing social conditions. But bear in mind that personal characteristics need not change everywhere in society for crime’s aggregate level in society to change. Consider age, for example, since crime is mainly the business of young people between 15 and 24.6 When the age distribution of the population shifts toward more people in their peak years for crime, the average level of crime may be expected to rise. Or crime may rise disproportionately if a large bulge in the youthful sector of the population fosters a youth culture that relishes unconventionality over traditional adult values. The exploding crime rate of the 1960s is, for example, partly explained by the baby boomers’ reaching adolescence.7 Or suppose that a style of child rearing sweeps the country, and it turns out that this style of child rearing leads to less control over the behavior of rebellious adolescents. The change in style of child rearing may predictably be followed, fifteen or so years later, by a change in crime rates. If, in short, circumstances tip toward crime, the change will show up most among those with the strongest tendencies to break laws (or the weakest tendencies to obey them).8 Understanding those tendencies is the business of theories at the psychological pole.

Argument 2: Behavior is criminal only because society says so. There cannot be psychological tendencies to engage in behavior defined so arbitrarily.

This argument, made frequently during the 1960s and 1970s and always more popular among intellectuals than with the general public, is heard most often opposing any suggestion that criminal behavior has biological roots. How can something so arbitrary, say, as not paying one’s taxes or driving above a 55 mph speed limit be inherited? the critics ask. Behavior regarding taxes and speed limits certainly cannot be coded in our DNA; perhaps even more elemental behaviors such as robbery and murder cannot either.

Our counterargument goes like this: Instead of crime, consider behavior that is less controversial and even more arbitrary, like playing the violin. A violin is a cultural artifact, no less arbitrary than any other man-made object, and so is the musical scale. Yet few people would argue that the first violinists in the nation’s great orchestras are a random sample of the population. The interests, talents, self-discipline, and dedication that it takes to reach their level of accomplishment have roots in individual psychology—quite possibly even in biology. The variation across people in any behavior, however arbitrary, will have such roots. To that we may add that the core crimes represented in the violent crime and property crime indexes—murder, robbery, and assault—are really not so arbitrary, unless the moral codes of human cultures throughout the world may be said to be consistently arbitrary in pretty much the same way throughout recorded human history.

But even if crime is admitted to be a psychological phenomenon, why should intelligence be important? What is the logic that might lead us to expect low intelligence to be more frequently linked with criminal tendencies than high intelligence is?9

One chain of reasoning starts from the observation that low intelligence often translates into failure and frustration in school and in the job market. If, for example, people of low intelligence have a hard time finding a job, they might have more reason to commit crimes as a way of making a living. If people of low intelligence have a hard time acquiring status through the ordinary ways, crime might seem like a good alternative route. At the least, their failures in school and at work may foster resentment toward society and its laws.

Perhaps the link between crime and low IQ is even more direct. A lack of foresight, which is often associated with low IQ, raises the attractions of the immediate gains from crime and lowers the strength of the deterrents, which come later (if they come at all). To a person of low intelligence, the threats of apprehension and prison may fade to meaninglessness. They are too abstract, too far in the future, too uncertain.

Low IQ may be part of a broader complex of factors. An appetite for danger, a stronger-than-average hunger for the things that you can get only by stealing if you cannot buy them, an antipathy toward conventionality, an insensitivity to pain or to social ostracism, and a host of derangements of various sorts, combined with low IQ, may set the stage for a criminal career.

Finally, there are moral considerations. Perhaps the ethical principles for not committing crimes are less accessible (or less persuasive) to people of low intelligence. They find it harder to understand why robbing someone is wrong, find it harder to appreciate the values of civil and cooperative social life, and are accordingly less inhibited from acting in ways that are hurtful to other people and to the community at large.

With these preliminaries in mind, let us explore the thesis that, whatever the underlying reasons might be, the people who lapse into criminal behavior are distinguishable from the population at large in their distribution of intelligence.


The statistical association between crime and cognitive ability has been known since intelligence testing began in earnest. The British physician Charles Goring mentioned a lack of intelligence as one of the distinguishing traits of the prison population that he described in a landmark contribution to modern criminology early in the century.10 In 1914, H. H. Goddard, an early leader in both modern criminology and the use of intelligence tests, concluded that a large fraction of convicts were intellectually subnormal.11

The subsequent history of the study of the link between IQ and crime replays the larger story of intelligence testing, with the main difference being that the attack on the IQ/crime link began earlier than the broader attempt to discredit IQ tests. Even in the 1920s, the link was called into question, for example, by psychologist Carl Murchison, who produced data showing that the prisoners of Leavenworth had a higher mean IQ than that of enlisted men in World War I.12 Then in 1931, Edwin Sutherland, America’s most prominent criminologist, wrote “Mental Deficiency and Crime,” an article that effectively put an end to the study of IQ and crime for half a century.13 Observing (accurately) that the ostensible IQ differences between criminals and the general population were diminishing as testing procedures improved, Sutherland leaped to the conclusion that the remaining differences would disappear altogether as the state of the art improved.

The difference, in fact, did not disappear, but that did not stop criminology from denying the importance of IQ as a predictor of criminal behavior. For decades, criminologists who followed Sutherland argued that the IQ numbers said nothing about a real difference in intelligence between offenders and nonoffenders. They were skeptical about whether the convicts in prisons were truly representative of offenders in general, and they disparaged the tests’ validity. Weren’t tests just measuring socioeconomic status by other means, and weren’t they biased against the people from the lower socioeconomic classes or the minority groups who were most likely to break the law for other reasons? they asked. By the 1960s, the association between intelligence and crime was altogether dismissed in criminology textbooks, and so it remained until recently. By the end of the 1970s, students taking introductory courses in criminology could read in one widely used textbook that the belief in a correlation between low intelligence and crime “has almost disappeared in recent years as a consequence of more cogent research findings,”14 or learn from another standard textbook of “the practical abandonment of feeblemindedness as a cause of crime.”15

It took two of the leading criminologists of another generation, Travis Hirschi and Michael Hindelang, to resurrect the study of IQ and criminality that Sutherland had buried. In their 1977 article, “Intelligence and Delinquency: A Revisionist View,” they reviewed many studies that included IQ measures, took into account the potential artifacts, and concluded that juvenile delinquents were in fact characterized by substantially below-average levels of tested intelligence.16 Hirschi and Hindelang’s work took a while to percolate through the academy (the author of the 1982 edition of one of the textbooks quoted above continued to make no mention whatever of IQ),17 but by the end of the 1980s, most criminologists accepted not just that an IQ gap separates offenders and nonoffenders, but that the gap is genuinely a difference in average intellectual level or, as it is sometimes euphemistically called, “academic competence,” Criminology textbooks now routinely report the correlation between crime and intelligence, and although some questions of interpretation are still open, they are narrower than they used to be because the correlation itself is no longer in dispute.18

The Size of the IQ Gap

How big is the difference between criminals and the rest of us? Taking the literature as a whole, incarcerated offenders average an IQ of about 92, 8 points below the mean. The population of nonoffenders averages more than 100 points; an informed guess puts the gap between offenders and nonoffenders at about 10 points.19 More serious or more chronic offenders generally have lower scores than more casual offenders.20 The eventual relationship between IQ and repeat offending is already presaged in IQ scores taken when the children are 4 years old.21

Not only is there a gap in IQ between offenders and nonoffenders, but a disproportionately large fraction of all crime is committed by people toward the low end of the scale of intelligence. For example, in a twenty-year longitudinal study of over 500 hundred boys in an unidentified Swedish community, 30 percent of all arrests of the men by the age of 30 were of the 6 percent with IQs below 77 (at the age of 10) and 80 percent were of those with IQs below 100.22 However, it stands to reason (and is supported by the data) that the population of offenders is short of very low-scoring persons—people whose scores are so low that they have trouble mustering the competence to commit most crimes.23 A sufficiently low IQ is, in addition, usually enough to exempt a person from criminal prosecution.24

Do the Unintelligent Ones Commit More Crimes—or Just Get Caught More Often?

Some critics continue to argue that offenders whose IQs we know are unrepresentative of the true criminal population; the smart ones presumably slipped through the net. Surely this is correct to some degree. If intelligence has anything to do with a person’s general competence, then it is not implausible that smart criminals get arrested less often because they pick safer crimes or because they execute their crimes more skillfully.25 But how much of a bias does this introduce into the data? Is there a population of uncaught offenders with high IQs committing large numbers of crimes? The answer seems to be no. The crimes we can trace to the millions of offenders who do pass through the criminal justice system and whose IQs are known account for much of the crime around us, particularly the serious crime. There is no evidence for any other large population of offenders, and barely enough crime left unaccounted for to permit such a population’s existence.

In the small amount of data available, the IQs of uncaught offenders are not measurably different from the ones who get caught.26 Among those who have criminal records, there is still a significant negative correlation between IQ and frequency of offending.27 Both of these kinds of evidence imply that differential arrests of people with varying IQs, assuming they exist, are a minor factor in the aggregate data.

Intelligence as a Preventative

Looking at the opposite side of the picture, those who do not commit crimes, it appears that high cognitive ability protects a person from becoming a criminal even if the other precursors are present. One study followed a sample of almost 1,500 boys born in Copenhagen, Denmark, between 1936 and 1938.28 Sons whose fathers had a prison record were almost six times as likely to have a prison record themselves (by the age of 34-36) as the sons of men who had no police record of any sort. Among these high-risk sons, the ones who had no police record at all had IQ scores one standard deviation higher than the sons who had a police record.29

The protective power of elevated intelligence also shows up in a New Zealand study. Boys and girls were divided on the basis of their behavior by the age of 5 into high and low risk for delinquency. High-risk children were more than twice as likely to become delinquent by their mid-teens as low-risk children. The high-risk boys or girls who did not become delinquent were the ones with the higher IQs. This was also true for the low-risk boys and girls: The nondelinquents had higher IQs than the delinquents.30

Children growing up in troubled circumstances on Kauai in the Hawaiian chain confirm the pattern. Several hundred children were followed in a longitudinal study for several decades.31 Some of the children were identified by their second birthday as being statistically “vulnerable” to behavioral disorders or delinquency. These were children suffering from two or more of the following circumstances: they were being raised in troubled or impoverished families; had alcoholic, psychologically disturbed, or unschooled (eight years or less of schooling) parents; or had experienced prenatal or perinatal physiological stress. Two-thirds of these children succumbed to delinquency or other psychological disturbances. But how about the other third, the ones who grew up without becoming delinquents or disturbed psychologically? Prominent among the protective factors were higher intellectual ability scores than the average for the vulnerable group.32


In the United States, where crime and race have become so intertwined in the public mind, it is especially instructive to focus on just whites. To simplify matters, we also limit the NLSY sample to males. Crime is still overwhelmingly a man’s vice. Among whites in the sample, 83 percent of all persons who admitted to a criminal conviction were male.

The Rest of the Story

The statistically distinguishable personal characteristics of criminals go far beyond IQ. There is, for example, the enormous difference between the levels of male and female criminality, which cannot be explained by intellectual differences between the sexes. Accounts of the rapidly expanding literature on the psychological and biological correlates of criminality, which has become highly informative about everything from genes to early childhood precursors, may be tracked in numerous scientific journals and books.33 Probably as much could be learned about individual differences beyond intelligence that characterize the chronically unemployed, unmarried mothers, neglectful parents, and others who have been the subjects of the other chapters in Part II. But that is just surmise at this point. The necessary research has either not been done at all or has been done in only the sketchiest way.34

Interpreting Self-Report Data

In the 1980 interview wave, the members of the NLSY sample were asked detailed questions about their criminal activity and their involvement with the criminal justice system. These data are known as self-report data, meaning that we have to go on what the respondent says. One obvious advantage of self-reports is that they presumably include information about the crimes of offenders whether or not they have been caught. Another is that they circumvent any biases in the criminal justice system, which, some people argue, contaminate official criminal statistics. But can self-report data be trusted? Criminologists have explored this question for many years, and the answer is yes, but only if the data are treated gingerly. Different racial groups have different response patterns, and these are compounded by differences between the genders.35 Other issues are discussed in the note.36

Our use of the NLSY self-report data sidesteps some of the problems by limiting the analysis to one ethnic group and one gender: white males. Given the remaining problems with self-report data, we will concentrate in this analysis on events that are on the public record (and the respondent knows are on the public record): being stopped by the police, formal charges, and convictions. In doing so, we are following a broad finding in crime research that official contacts with the law enforcement and criminal justice system are usefully accurate reflections of the underlying level of criminal activity.37 At the end of the discussion, we show briefly that using self-report data on undetected crimes reinforces the conclusions drawn from the data on detected crimes.

IQ and Types of Criminal Involvement

The typical finding has been that between a third and a half of all juveniles are stopped by police at some time or another (a proportion that has grown over the last few decades) but that 5 to 7 percent of the population account for about half the total number of arrests.38 In the case of white males in the NLSY, 34 percent admitted having been stopped at some time by the police (for anything other than a minor traffic violation), but only 3 percent of all white males accounted for half of the self-reported “stops.”

Something similar applies as we move up the ladder of criminal severity. Only 18 percent of white males had ever formally been charged with an offense, and a little less than 3 percent of them accounted for half the charges. Only 13 percent of white males had ever been convicted of anything, and 2 percent accounted for half of the convictions. Based on these self-reports, a very small minority of white males had serious criminal records while they were in this 15 to 23 age range.

Like studies using all races, the NLSY results for white males show a regular relationship between IQ and criminality. The table below presents the average IQs of white males who had penetrated to varying levels of the criminal justice system as of the 1980 interview.39 Those who reported they had never even been stopped by the police (for anything other than a minor traffic violation) were above average in intelligence, with a mean IQ of 106, and things went downhill from there. Close to a standard deviation separated those who had never been stopped by the police from those who went to prison.

Criminality and IQ Among White Males

Deepest Level of Contact with the Criminal Justice System

Mean IQ



Stopped by the police but not booked


Booked but not convicted


Convicted but not incarcerated


Sentenced to a correctional facility


A similar pattern emerges when the criminal involvements are sorted by cognitive class, as shown in the next table. Involvement with the criminal justice system rises as IQ falls from Classes I through IV. Then we reach Class V, with IQs under 75, If we take the responses at face value, the Class Vs are stopped, charged, and convicted at lower rates than the Class IVs but are sentenced to correctional facilities at rates almost exactly the same rate. We noted earlier that people at the lowest levels of intelligence are likely to be underrepresented in criminal statistics, and so it is in the NLSY, It may be that the offenses of the Class Vs are less frequent but more serious than those of the Class IVs or that they are less competent in getting favorable treatment from the criminal justice system. The data give us no way to tell.

The Odds of Getting Involved with the Police and Courts for Young White Males

Percentage Who in 1980 Reported Ever Having Been:

Cognitive Class

Stopped by the Police

Booked for an Offense

Convicted of an Offense

Sentenced to Incarceration

I Very bright





II Bright





III Normal





IV Dull





V Very dull










In addition to self-reports, the NLSY provides data on criminal behavior by noting where the person was interviewed. In all the interviews from 1979 to 1990, was the young man ever interviewed in a correctional facility? The odds shown in the table below (computed from the unrounded results) that a white male had ever been interviewed in jail were fourteen times greater for Class V than for white males anywhere in the top quartile of IQ.

The Odds of Doing Time for Young White Males

Cognitive Class

Percentage Ever Interviewed in a Correctional Facility

I Very bright


II Bright


III Normal


IV Dull


V Very dull




Being incarcerated at the time of the interview signifies not just breaking the law and serving time but also something about the duration of the sentence, which may explain the large increase at the bottom of the ability distribution. The NLSY sample of white males echoes the scientific literature in general in showing a sizable IQ gap between offenders and nonoffenders at each level of involvement with the criminal justice system.

The Role of Socioeconomic Background

We will use both self-reports and whether the interviewee was incarcerated at the time of the interview as measures of criminal behavior. The self-reports are from the NLSY men in 1980, when they were still in their teens or just out of them. It combines reports of misdemeanors, drug offenses, property offenses, and violent offenses. Our definition of criminality here is that the man’s description of his own behavior put him in the top decile of frequency of self-reported criminal activity.40 The other measure is whether the man was ever interviewed while being confined in a correctional facility between 1979 and 1990. When we run our standard analysis for these two different measures, we get the results in the next figure.

Both measures of criminality have weaknesses but different weaknesses. One relies on self-reports but has the virtue of including uncaught criminality; the other relies on the workings of the criminal justice system but has the virtue of identifying people who almost certainly have committed serious offenses. For both measures, after controlling for IQ, the men’s socioeconomic background had little or nothing to do with crime. In the case of the self-report data, higher socioeconomic status was associated with higher reported crime after controlling for IQ. In the case of incarceration, the role of socioeconomic background was close to nil after controlling for IQ, and statistically insignificant. By either measure of crime, a low IQ was a significant risk factor.

On two diverse measures of crime, the importance of IQ dominates socioeconomic background for white men


Note: For computing the plot, age and either SES (for the black curves) or IQ (for the gray curves) were set at their mean values.

The Role of a Broken Home

When people think about the causes of crime, they usually think not only of the role of juvenile delinquent’s age and socioeconomic background but also of what used to be called “broken homes.” It is now an inadequate phrase, because many families do not even begin with a married husband and wife, and many broken homes are reconstituted (in some sense) through remarriage. But whatever the specific way in which a home is not intact, the children of such families are usually more likely to get in trouble with the law than children from intact families.41 This was true for the NLSY white males. An intact family consisting of the biological mother and father was associated with better outcomes for their children than any of the other family arrangements. Was the young man ever stopped by the police? Thirty-two percent of white males from intact families compared to 46 percent of all others. Booked for an offense? Fifteen percent compared to 29 percent. Convicted of an offense? Eleven percent compared to 21 percent. Sentenced to a correctional facility? Two percent compared to 7 percent.

Although family setting had an impact on crime, it did not explain away the predictive power of IQ. For example, a young man from a broken family and an average IQ and socioeconomic background had a 4 percent chance of having been interviewed in jail. Switch his IQ to the 2d centile, and the odds rise to 22 percent. (Switch his socioeconomic background to the 2d centile instead, and the odds rise only from 4 to 5 percent.) The same conclusions apply to the measure of self-reported crime.

The Role of Education

Scholars have been arguing about the relationship of education to crime and delinquency for many years without settling the issue. The case of the NLSY white males is a classic example. Of those who were ever interviewed in jail, 74 percent had not gotten a high school diploma. None had a college degree. Clearly something about getting seriously involved in crime competes with staying in school. Low IQ is part of that “something” in many cases, but the relationship is so strong that other factors are probably involved—for example, the same youngster who is willing to burglarize a house probably is not the most obedient of pupils; the youngster who commits assaults on the street probably gets in fights on the school grounds; the youngster who is undeterred by the prospect of jail time probably is not much motivated by the prospect of getting a high school degree; and so forth.

Does high school dropout actually cause the subsequent crime? Many people assumed so until Delbert Elliott and Harwin Voss published a study in 1974 that concluded the opposite: Crime diminished after school dropout.42Since then, everyone has agreed that eventual dropouts tend to have high levels of criminal activity while they are in school, but disputes remain about whether the rates fall or rise after the dropout occurs.43

For our purposes, it makes little sense to examine the continuing role of IQ in our usual educational samples when the action is so conspicuously concentrated among those who fall neither in the high school nor the college graduate samples. Running our standard analysis on white males who did not get a high school diploma did not shed much more light on the matter.44 Given the restriction of range in the sample (the mean IQ of the white male dropout sample was 91, with a standard deviation of only 12.5), not much can be concluded from the fact that the ones at the very bottom of the cognitive ability distribution were less likely to report high levels of criminal activity. For these school dropouts, the likelihood of having been interviewed in jail rose as IQ fell, but the relationship was weaker than for the unrestricted sample of white males.


By now, you will already be anticipating the usual caution: Despite the relationship of low IQ to criminality, the great majority of people with low cognitive ability are law abiding. We will also take this opportunity to reiterate that the increase in crime over the last thirty years (like the increases in illegitimacy and welfare) cannot be attributed to changes in intelligence but rather must be blamed on other factors, which may have put people of low cognitive ability at greater risk than before.

The caveats should not obscure the importance of the relationship of cognitive ability to crime, however. Many people tend to think of criminals as coming from the wrong side of the tracks. They are correct, insofar as that is where people of low cognitive ability disproportionately live. They are also correct insofar as people who live on the right side of the tracks—whether they are rich or just steadily employed working-class people—seldom show up in the nation’s prisons. But the assumption that too glibly follows from these observations is that the economic and social disadvantage is in itself the cause of criminal behavior. That is not what the data say, however. In trying to understand how to deal with the crime problem, much of the attention now given to problems of poverty and unemployment should be shifted to another question altogether: coping with cognitive disadvantage. We will return to this question in the final chapter, when we consider policy changes that might make it easier for everyone to live within the law.