Lecture Elaboration: Rising IQ Scores
An individual's IQ score remains relatively constant across their lifespan. Recently researchers have been addressing a different type of stability (or instability) in IQ scores--the fact that IQ scores have been steadily increasing in developed countries over the past 50 or 60 years. The so-called "Flynn effect" provides for an interesting discussion of environmental and cultural impact on IQ. The effect is named after political scientist James Flynn, who has researched this effect extensively. Azar (1996) reports in the APA Monitor on a recent (1996) conference of experts that focused on reasons for the Flynn effect. The APA-sponsored conference was titled "Intelligence on the rise: secular changes in IQ and related measures."
A particularly striking statistic is that the average IQ of a 20-year old in 1996 is approximately 15 points higher than that of a 20-year old 50 years ago. Most suspect that the rising IQ scores do not reflect a change in g, the global intelligence purportedly measured by traditional tests. Rather, escalating scores are thought to be the product of more specific skills that allow people to excel on tasks like those included in these tests, along with improved socioeconomic status, better nutrition, and an increasingly technological society.
According to Azar's (1996) report, the increase in IQ scores differs somewhat, depending on the particular measure used to assess intelligence. On the Raven's Progressive Matrices IQ test, which emphasizes visuo-spatial skills, the increase has been dramatic. The maximum score on this test is 60 points; people (born in 1877) tested in 1942 scored an average 24, while people (born in 1967) tested in 1992 scored an average of 54! Because IQ is based on average score of a population, both were said to have an IQ of 100 in their respective generations. It should also be noted that these two samples were of substantially different ages when they took the test (65 and 25), but this difference is not likely to be the only cause of the IQ score discrepancy.
The increase in average IQ scores has not been as dramatic for traditional intelligence tests such as the Stanford-Binet and the Wechsler Adult Intelligence Scale. These tests, in addition to testing visuo-spatial ability, also test more verbally-acquired, school-taught knowledge such as vocabulary, general knowledge, and arithmetic. The fact that scores on traditional tests of intelligence has not increased as dramatically suggests that the increases are the product of skills that aren't particularly affected by schooling. Also, Ulric Neisser, who organized the conference, argues that the rapidity of the increase argues against a genetic explanation. According to Neisser, the reason must be environmental.
What environmental changes might account for rising IQ scores? The article reports a number of possible factors. First, the technology boom seen since the industrial revolution has made people more adept at skills that are measured on IQ tests. Our society has become increasingly visual ever since the advent of movies in the 1920's. Neisser believes that this experience and practice with visual manipulation has led to an enhancement of these skills, and a corresponding rise in IQ. Some also cite the video game as a possible source of enhanced performance on visuo-spatial components of IQ tests.
Others cite improvements in social conditions as a possible cause of the Flynn effect. Better nutrition in industrialized countries has led to a decrease in low-birth-weight babies, and a decrease in cases of malnutrition and nutrient deficiencies.
Another likely factor driving increases in IQ is the level of parents education. Steven Ceci notes that the more education a parent has, the higher their child's IQ--from the mid-1970's to 1990, the number of parents who had attended college rose 70% for non-minorities, 350% for minorities.
The Monitor article also reports that gaps between achievement
test scores of Whites and African- Americans in the U.S. showed a substantial
decrease from 1971 to 1990. Researchers Robert Hauser and David Grissmer
note that this is a period when the federal government was investing more
money in educational programs directed at equalizing opportunity for minority
children. Also, the greatest gains in IQ were shown by those with the lowest
scores. These findings support the promising conclusion that environmental
factors, such as improvements in the educational system, can produce changes
in intelligence., The Flynn effect and its probable causes demonstrate
that intellectual ability is not an immutable, unchanging characteristic.
Azar, B. (1996, June). People are becoming smarter—why? APA Monitor.