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The secret behind IQ: Is our intelligence really related to genetics?
Intelligence quotient (IQ) is an overall score that assesses human intelligence through standardized tests or subtests. The concept of IQ was first obtained by dividing a person's mental age by their chronological age and then multiplying by 100. However, over time, the methods and functions of modern IQ tests have changed significantly.
IQ scores are affected by a variety of factors, including nutrition, parents' socioeconomic status, and an individual's birth environment.
The heritability of IQ scores has been studied for nearly a century, but its importance and genetic mechanisms remain controversial. Research shows that IQ scores are closely linked to educational achievement, occupational performance and income levels. In countless IQ tests, people's scores tend to gradually rise over time, a phenomenon known as the "Flynn effect."
Historical background of IQ
Before the advent of IQ tests, people attempted to classify an individual's intelligence by observing behavior. British statistician Francis Galton first proposed standardized testing of intelligence. He believed that intelligence was primarily a manifestation of heredity rather than the result of nurture. Although Galton's research lacked substantial evidence, he laid the foundation for future IQ tests.
The diversity of intelligence is not limited to what IQ tests can show, but also requires qualitative assessment for in-depth understanding.
The Binet-Simon intelligence test, published in 1905 by French psychologist Alfred Binet and psychiatrist Theodore Simon, is based on language ability and is mainly used to identify intellectual disabilities in school-age children. This intelligence test spurred research in the United States and the development of its later forms of IQ testing.
IQ and the Eugenics Movement
The eugenics movement in the United States gained attention in the early 20th century, and this movement was closely related to the popularization of IQ testing. Through intelligence tests, this movement hopes to eliminate "bad" genes and thereby "improve" the intelligence level of the entire population. The famous psychologist Henry Goddard used the Binet-Simon test to promote eugenics, in which the label "stupid" was applied to people with lower IQ scores.
There are still disagreements and debates in the contemporary scientific community about the relationship between IQ and heredity.
Over time, definitions and methods of measuring intelligence have become more diverse. As a large number of studies have shown the complexity of intelligence, different theories such as the Cattell-Horn-Carroll theory have emerged, which attempt to conduct a more detailed analysis of the causes and specific manifestations of intelligence. Modern IQ tests no longer just give a simple score, but provide a multidimensional assessment that includes specific abilities.
Reliability and validity of current IQ tests
Modern IQ tests such as the Wechsler Intelligence Scale for Adults (WAIS) and the Wechsler Intelligence Scale for Children (WISC) do not only rely on a single indicator, but evaluate different dimensions. These tests are designed to more comprehensively reflect an individual's intellectual structure, such as the distinction between fluid intelligence and crystallized intelligence, which clarifies the diversity of intelligence.
Although today's IQ tests have introduced more dimensions to evaluate individuals, the extent to which intelligence is affected by genetics is still an important issue.
Over the past few decades, the study of intelligence and its measurement have undergone numerous changes, yet the persistent problem of predicting IQ based on genetic factors remains. This has prompted scientists to continue to explore the many factors related to intelligence and to try to sort out the ethical and social implications of this process. In this context, whether IQ as an indicator can comprehensively and accurately reflect a person's intelligence level has become one of the hot topics in current scientific discussion. People can't help but ask: What is the nature of intelligence? Will the excessive emphasis on IQ neglect the development of other more important qualities and abilities?
