From the early 1930s and beyond, IQ tests were periodically restandardized. This meant that the researchers had to administer the IQ tests to a large number of people and set the average performance at 100. However, it was discovered that people, on average, were achieving scores substantially higher than 100 on the same IQ tests as those involved in the earlier standardization. This upward drift in IQ of about one standard deviation (15 points) every two generations is now known as the Flynn effect, in recognition of James R. Flynn’s discussion of its potential causes and implications.
In his TED Talk, presented on September 26, 2013, (see: Why our IQ levels are higher than our grandparents’) Flynn hypothesized that the new technologies including radio, television, and computers are demanding more abstract thought than the environment of the early 20th century. He noted that in 1900, only 3% of jobs were cognitively demanding, including occupations such as doctor, lawyer, teacher, and accountant. He compared this to the 35% of jobs today that demand higher order thinking skills. Flynn asserted that the high-tech environment is stimulating a latent capacity for abstract thought that was not as strongly demanded in previous generations. In his seminal publication, Principles of Psychology, Herbert Spencer defined the intelligence of an organism as “an adjustment of inner to outer relations,” meaning the organism’s ability to adapt to its environment.
The rapid increase in IQ in two generations is too fast to be attributed to genetic mutation so Flynn and others conjectured that intelligence was increased by the demands of our technological society. Research in the newly emerging field of epigenetics suggests that environmental influences can “switch on” and “switch off” certain genes, while research in neuroplasticity has shown how the brain, after suffering injury, can “rewire” its synaptic connections.
To further complicate the issue, recent studies have revealed that while IQ scores increased between 1930 and 2000 (positive Flynn effect), IQ scores declined in subsequent decades (negative Flynn effect) in some countries–a decline that some researchers attribute to environmental effects such as declining educational standards and passive technologies.
Flynn has recently acknowledged that the positive Flynn effect may have been a result of the fact that today, a substantially greater portion of the world population has access to education and nutrition than in previous generations, reducing the number of people who perform poorly on IQ tests from deficient reading skills or proper nutrition during their formative years. Others have suggested that the demographic used to norm the IQ tests included a greater proportion people who were familiar with the process of taking tests than those of earlier generations.
The subsequent negative Flynn effect challenged some of the explanations advanced for the positive Flynn effect. Some psychologists attributed the reversal of the Flynn effect to the fact that those in the educated class are having fewer children than the those in the lower socioeconomic groups. Since those of high IQ are usually in the educated class, this implies that the offspring of the high IQ people are becoming a smaller percentage of the gene pool. Psychologists refer to this effect as “dysgenic,” because it acts as “negative” natural selection by a preferential selection of those of lower IQ. (see: Hong, Z. (2020). Modelling the on-going natural selection of educational attainment in contemporary societies. Journal of theoretical biology, 493, 110210.
Conclusion
Some of the causes of confusion over the Flynn effect and its reverse result from the assumption that a person’s IQ is a fixed entity that doesn’t change over a lifetime. However, the Cattell model of intelligence asserts that intelligence has two components: fluid intelligence and crystallized intelligence. Fluid intelligence is your brain’s neural efficiency, i.e., its processing power, while crystallized intelligence is your accumulated experience and knowledge. While your fluid intelligence is determined by your DNA, your crystallized intelligence is acquired by your experiences and learning throughout your life. (For a more detailed explanation, see: What is fluid intelligence? How does it differ and what is it used for? In comparison to regular intelligence. – Intelligence and IQ )
Throughout the 20th century, the fluid intelligence of humans did not change. However, the crystallized intelligence of humans increased as nutrition and education became more accessible. With the increase in crystallized intelligence came a measurable increase in intelligence as measured by IQ tests. However, the dysgenic effect of the higher reproduction in the lower SES classes may have outpaced the positive Flynn effect and let to a net decline in average IQ on a global basis.
