The Flynn Effect: Are IQ's Rising?

The "Flynn effect" is named after political scientist James Flynn, who has researched the environmental and cultural impact on IQ. Azar (1996) reports in the APA Monitor 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.  The article, titled, “People are becoming smarter—why?” postulates that the rising IQ scores do not reflect a change in the global intelligence purportedly measured by traditional tests. Azar hypothesizes that escalating scores are 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.

Most researchers agree that genetic factors account for about 40-80% of the variation in IQ test results. If this is true, then environmental or other factors must account for 20-60% - which is a large range.

Some environmental factors that have a large effect upon later IQ test results include prenatal ones, such as:

• Whether or not, prior to the birth, mother drank large amounts of alcohol during her pregnancy (fetal alcohol syndrome).
• The mother was exposed to large amounts of lead.
• Schooling.
• The quality of toys used.
• The amount of external stimulus the child was subjected to.
• Prolonged malnutrition also has a marked negative effect on IQ test.
• In contrast, babies who were breastfed have IQs up to 10 points on average higher than those who weren’t

According to Azar, IQ scores gains differ 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. Researchers have argued that the rapidity of the increase does not have a genetic explanation.  The increase must then 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. It is possible 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.

Summary of Studies Into Factors that Influence IQ

Evidence of genetic influences:

• Twin studies suggest that identical twins IQ's are more similar than those of fraternal twins (Promin & Spinath, 2004).
• Siblings reared together in the same home have IQ's that are more similar than those of adopted children raised together in the same environment (McGue & others, 1993).

Evidence of environmental influences:

• Identical twins reared apart have IQ's that are less similar than identical twins reared in the same environment (McGue & others, 1993).
• School attendance has an impact on IQ scores (Ceci, 2001).
• Children who are breastfed during the first three to five months of life score higher on IQ tests at age 6 than same-age children who were not breastfed (Reinberg, 2008).

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.

If your child attends Pinellas, Hillsborough, Pasco, or Manatee County Public Schools and you are interested in AGP assessment or Gifted assessment for your child, or if you just live in the Tampa area and want to know your child’s IQ score, please use the Contact Form to schedule an appointment of call Dr. Bishop at (813) 774-6340