Human Intelligence has a very good summary of the Bell Curve book:
The Bell Curve, published in 1994, was written by Richard Herrnstein and Charles Murray as a work designed to explain, using empirical statistical analysis, the variations in intelligence in American Society, raise some warnings regarding the consequences of this intelligence gap, and propose national social policy with the goal of mitigating the worst of the consequences attributed to this intelligence gap. Many of the assertions put forth and conclusions reached by the authors are very controversial, ranging from the relationships between low measured intelligence and anti-social behavior, to the observed relationship between low African-American test scores (compared to whites and Asians) and genetic factors in intelligence abilities. The book was released and received with a large public response. In the first several months of its release, 400,000 copies of the book were sold around the world. Several thousand reviews and commentaries have been written in the short time since the book’s publication….
The Bell Curve, in its introduction, begins with a brief description of the history of intelligence theory and recent developments in intelligence thought and testing, through the eyes of the authors. The introduction concludes with six important assumptions that the authors build much of the Bell Curve’s case upon. These six assumptions regarding the validity of “classical” cognitive testing techniques include:
There is such a difference as a general factor of cognitive ability on which human beings differ.
All standardized test of academic aptitude or achievement measure this general factor to some degree, but IQ tests expressly designed for that purpose measure it most accurately.
IQ scores match, to a first degree, whatever it is that people mean when they use the word intelligent, or smart in ordinary language.
IQ scores are stable, although not perfectly so, over much of a person’s life.
Properly administered IQ tests are not demonstrably biased against social, economic, ethnic, or racial groups.
Cognitive ability is substantially heritable, apparently no less than 40 percent and no more than 80 percent.
The authors proceed to explain, using classical cognitive test results primarily, to explain how lower levels of measured intelligence impact an individual’s, or indeed an entire class or group of individual’s life in American society. The rest of the book is divided into four major parts. http://www.indiana.edu/~intell/bellcurve.shtml
Needless to say, this book ignited a firestorm.
Cam Soucy wrote an excellent summary of IQ tests for the Livestrong site in the article, What Is the Definition of IQ Test?
History
French psychologist Alfred Binet developed the the first IQ-style tests at the beginning of the 20th century. The first tests were designed only to assess the intelligence of children. The U.S. military relied on intelligence testing to assess and place recruits during World Wars I and II. Psychologist David Wechsler used the military IQ tests as a model in devising his own test in 1949. Today, a group of tests derived from Wechsler’s work are the most widely used IQ tests.
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Tests
The fourth version of the Wechsler Intelligence Scale for Children, the WISC-IV, was released in 2009. A companion test, the Wechsler Adult Intelligence Scale, targets people 16 and older. Other frequently used IQ tests include the Stanford-Binet Intelligence Scale, the Das-Naglieri Cognitive Assessment System and the Kaufman Assessment Battery for Children.
Elements
IQ tests commonly assess the taker’s logical reasoning, math ability, spatial-relations skills, short-term memory and problem-solving skills.
Scoring
IQ tests originally were scored by dividing the subject’s “mental age,” as determined by which questions she answered correctly on the test, by her “chronological age,” her actual age in years, then multiplying that quotient by 100. For example, an 8-year-old child with a mental age of 12 would have an IQ of 125, with the calculation being 12/8 = 1.25, and 1.25 x 100 = 125. A person whose mental age precisely matched his actual age would have an IQ of 100, so a 100 IQ was defined as “average.”
Modern IQ tests no longer use such a formula. They simply compare a person’s test results with those of everyone else in the same age group, on a scale where 100 is defined as average intelligence.
Criticism
Criticism of IQ tests focuses on the content of the tests–that is, the type of questions they ask–and their application. Such areas as vocabulary and “logic” can be strongly influenced by culture and socioeconomics. For example, consider a test that asks what word goes best with “cup”: saucer, plate or bowl. The test may intend “saucer” to be the correct answer. However, a test-taker who grew up in a home where tables weren’t set in a formal fashion might not know what a saucer is. He may be just as “intelligent” as the next person, but his score will suffer because of cultural factors. Authors of IQ tests are continually refining tests to address such concerns; some tests have removed verbal elements entirely.
Even test creators argue that the results are only one tool for assessing a person’s abilities, and that “intelligence” in a person is not a fixed quality, but changeable–even from day to day. In reality, however, people and institutions tend to put great weight on IQ scores. Students have been labeled “learning disabled” based on the outcome of IQ tests alone. As authors revise their tests, they also are revising their instructions to stress the tests’ limited application
http://www.livestrong.com/article/130019-definition-iq-test/
Daniel Willingham, cognitive scientist and a psychology professor at the University of Virginia and author of “Why Don’t Students Like School?” His next book, “When Can You Trust The Experts? How to tell good science from bad in education,” http://www.danielwillingham.com/books.html Willingham’s research is crucial for understanding IQ.
Science Daily reported in Falling IQ scores in childhood may signal psychotic disorders in later life:
New research shows adults who develop psychotic disorders experience declines in IQ during childhood and adolescence, falling progressively further behind their peers across a range of cognitive abilities. The researchers from King’s College London’s Institute of Psychiatry, Psychology & Neuroscience (IoPPN) and Icahn School of Medicine at Mount Sinai in the United States found falls in IQ start in early childhood, and suggest educational interventions could potentially delay the onset of mental illness.
Psychotic disorders, such as schizophrenia, are severe mental illnesses affecting 1-3% of the UK population that cause a range of abnormalities in perception and thinking. The study, published today in JAMA Psychiatry, is the first to track IQ scores and cognitive abilities throughout the entire first two decades of life among individuals who develop psychotic disorders in adulthood.
Dr Josephine Mollon from King’s IoPPN, now with Yale University, said: ‘For individuals with psychotic disorders, cognitive decline does not just begin in adulthood, when individuals start to experience symptoms such as hallucinations and delusions, but rather many years prior — when difficulties with intellectual tasks first emerge — and worsen over time. Our results suggest that among adults with a psychotic disorder, the first signs of cognitive decline are apparent as early as age 4.’
Previous studies have shown that deficits in IQ begin many years before hallucinations and delusions first appear in patients with psychotic disorders, but the timing of when these IQ deficits emerge has not been clear. The new study provides the clearest evidence to date of early life cognitive decline in individuals with psychotic disorders.
The study included 4322 UK-based individuals who were followed from 18 months to 20 years old. Those who developed psychotic disorders as adults had normal IQ scores in infancy, but by age 4 their IQ started to decline, and continued to drop throughout childhood, adolescence and early adulthood until they were an average of 15 points lower than their healthy peers… https://www.sciencedaily.com/releases/2018/01/180131133348.htm
Citation:
Falling IQ scores in childhood may signal psychotic disorders in later life
Date:
January 31, 2018
Source:
King’s College London
Summary:
New research shows adults who develop psychotic disorders experience declines in IQ during childhood and adolescence, falling progressively further behind their peers across a range of cognitive abilities. The researchers found falls in IQ start in early childhood, and suggest educational interventions could potentially delay the onset of mental illness.
Journal Reference:
1. Josephine Mollon, Anthony S. David, Stanley Zammit, Glyn Lewis, Abraham Reichenberg. Course of Cognitive Development From Infancy to Early Adulthood in the Psychosis Spectrum. JAMA Psychiatry, 2018; DOI: 10.1001/jamapsychiatry.2017.4327
Here is the press release from King’s College:
Falling IQ scores in childhood may signal psychotic disorders in later life
Posted on 01/02/2018
New research shows adults who develop psychotic disorders experience declines in IQ during childhood and adolescence, falling progressively further behind their peers across a range of cognitive abilities. The researchers from King’s College London’s Institute of Psychiatry, Psychology & Neuroscience (IoPPN) and Icahn School of Medicine at Mount Sinai in the United States found falls in IQ start in early childhood, and suggest educational interventions could potentially delay the onset of mental illness.
Psychotic disorders, such as schizophrenia, are severe mental illnesses affecting 1-3% of the UK population that cause a range of abnormalities in perception and thinking. The study, published today in JAMA Psychiatry, is the first to track IQ scores and cognitive abilities throughout the entire first two decades of life among individuals who develop psychotic disorders in adulthood.
Dr Josephine Mollon from King’s IoPPN, now with Yale University, said: ‘For individuals with psychotic disorders, cognitive decline does not just begin in adulthood, when individuals start to experience symptoms such as hallucinations and delusions, but rather many years prior – when difficulties with intellectual tasks first emerge – and worsen over time. Our results suggest that among adults with a psychotic disorder, the first signs of cognitive decline are apparent as early as age 4.’
Previous studies have shown that deficits in IQ begin many years before hallucinations and delusions first appear in patients with psychotic disorders, but the timing of when these IQ deficits emerge has not been clear. The new study provides the clearest evidence to date of early life cognitive decline in individuals with psychotic disorders.
The study included 4322 UK-based individuals who were followed from 18 months to 20 years old. Those who developed psychotic disorders as adults had normal IQ scores in infancy, but by age 4 their IQ started to decline, and continued to drop throughout childhood, adolescence and early adulthood until they were an average of 15 points lower than their healthy peers.
As well as falling behind in IQ, individuals who developed psychotic disorders lagged increasingly behind their peers in cognitive abilities such as working memory, processing speed and attention.
IQ scores fluctuate among healthy individuals, and not all children struggling at school are at risk of developing serious psychiatric disorders. Senior author Dr Abraham Reichenberg, Professor of Psychiatry at the Icahn School of Medicine at Mount Sinai and with King’s IoPPN said: ‘It is important to bear in mind that many children will experience some difficulties with schoolwork or other intellectual tasks at some point in their lives, and only a small minority will go on to develop a psychotic disorder.’
The results suggest that adults who develop psychotic disorders do not go through a deterioration in cognitive function, but instead they fail to keep up with normal developmental processes. Early interventions to improve cognitive abilities may potentially help stave off psychotic symptoms from developing in later life.
‘There are early interventions offered to adolescents and young adults with psychosis,’ said Dr Reichenberg. ‘Our results show the potential importance of interventions happening much earlier in life. Intervening in childhood or early adolescence may prevent cognitive abilities from worsening and this may even delay or prevent illness onset.’
The researchers are now examining changes in the brains of individuals who go on to develop psychotic disorders, as well as potential environmental and genetic risk factors that may predispose individuals to poor cognition.
The study was funded by the Medical Research Council, and the data was drawn from the Avon Longitudinal Study of Parents and Children (ALSPAC).
Notes to editors
Paper reference:
‘Course of Cognitive Development From Infancy to Early Adulthood in the Psychosis Spectrum’ by Mollon et al., JAMA Psychiatry, DOI: 10.1001/jamapsychiatry.2017.4327
To contact the authors, or for further media information, please contact: Robin Bisson, Senior Press Officer, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, robin.bisson@kcl.ac.uk / +44 20 7848 5377 / +44 7718 697176. +45 87165358
Here are some key findings of Intelligence: New Findings and Theoretical
Developments. American Psychologist. Advance online publication. doi: 10.1037/a0026699 which deal directly with the Bell Curve:
Stress, Intelligence, and Social Class
One factor that Neisser and colleagues (1996) did not deal with extensively is stress. Chronic, continuous stress—what can be considered as “toxic” stress—is injurious over time to organ systems, including the brain. Chronically high levels of stress hormones damage specific areas of the brain—namely, the neural circuitry of PFC and hippocampus—that are important for regulating attention and for short-term memory, long-term memory, and working memory (McEwen, 2000). Although the extent to which the effect of early stress on brain development and stress physiology may affect the development of intelligence is not currently known, we do know that (a) stress is greater in low-income home environments (Evans, 2004) and (b) a low level of stress is important for self-regulation and early learning in school (Blair & Razza, 2007; Ferrer & McArdle, 2004; Ferrer et al., 2007). Research suggests that part of the Black–White IQ gap may be attributable to the fact that Blacks, on average, tend to live in more stressful environments than do Whites. This is particularly the case in urban environments, where Black children are exposed to multiple stressors. Sharkey (2010), for example, has recently found that Black children living in Chicago (ages 5–17) scored between 0.5 and 0.66 SD worse on tests (both the WISC-Revised and the Wide Range Achievement Test-3) in the aftermath of a homicide in their neighborhood. Sharkey’s data show that debilitating effects were evident among children regardless of whether they were witnesses to the homicide or had simply heard about it. An impressive study by Eccleston (2011) indicates that even stress on the pregnant mother may have enduring effects on her children. The children born to women in New York City who were in the first six months of pregnancy when 9/11 occurred had lower birth weights than children born before 9/11 or well after it, and the boys at the age of six were more than 7% more likely to be in special education and more than 15% more likely to be in kindergarten rather than first grade. Oddly, girls’ academic status was unaffected by mothers’ stress. Investigation of relations between early stress and intelligence thus seems an important direction for future research. A particularly important issue concerns the degree to which the effects of stress on the brain are reversible. These five unresolved issues are merely examples of some of the important contemporary paradoxes and unknowns in intelligence research. It is to be hoped that as much progress on these and other issues will be made in the next 15 years as has been made on some of the paradoxes and unknowns since the time of the Neisser et al. (1996) review.
IQ is not a simple concept and this newest research points to more questions than answers.
Children will have the most success in school, if they are ready to learn. Ready to learn includes proper nutrition for a healthy body and the optimum situation for children is a healthy family. Many of societies’ problems would be lessened if the goal was a healthy child in a healthy family.
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