James R. Flynn

Massive IQ Gains in 14 Nations: What IQ Tests Really Measure

Data from 14 nations reveal IQ gains ranging from 5 to 25 points in a single generation. Some of the largest gains occur on culturally reduced tests and tests of fluid intelligence. The Norwegian data show that a nation can make significant gains on a culturally reduced test while suffering losses on other tests. The Dutch data prove the existence of unknown environmental factors so potent that they account for 15 of the 20 points gained. The hypothesis that best fits the results is that IQ tests do not measure intelligence but rather a correlate with a weak causal link to intelligence. This hypothesis can also explain differential trends on various mental tests, such as the combination of IQ gains and Scholastic Aptitude Test losses in the United States. Over the last decade, scholars in many countries—largely unknown to one another—have been measuring IQ trends from one generation to the next. In this article their results are collected and analyzed so as to reap the benefits comparative data usually yield. It is also argued that this mass of data poses fundamental problems for developmental psychology, primarily concerning what factors have the most potent effect on IQ, what IQ tests measure, and how IQ tests should be used in making between-groups comparisons.

The mean IQ of Americans: massive gains 1932 to 1978

This study shows that every Stanford-Binet and Wechsler standardization sample from 1932 to 1978 established norms of a higher standard than its predecessor. The obvious interpretation of this pattern is that representative samples of Americans did better and better on IQ tests over a period of 46 years, the total gain amounting to a rise in mean IQ of 13.8 points. The implications of this finding are developed: The combination of IQ gains and the decline in Scholastic Aptitude Test scores seems almost inexplicable; obsolete norms have acted as an unrecognized confounding variable in hundreds of studies; and IQ gains of this magnitude pose a serious problem of causal explanation.

Heritability Estimates Versus Large Environmental Effects: The IQ Paradox Resolved

Some argue that the high heritability of IQ renders purely environmental explanations for large IQ differences between groups implausible. Yet, large environmentally induced IQ gains between generations suggest an important role for environment in shaping IQ. The authors present a formal model of the process determining IQ in which peoples IQs are affected by both environment and genes, but in which their environments are matched to their IQs. The authors show how such a model allows very large effects for environment, even incorporating the highest estimates of heritability. Besides resolving the paradox, the authors show that the model can account for a number of other phenomena, some of which are anomalous when viewed from the standard perspective.

WAIS-III AND WISC-III IQ GAINS IN THE UNITED STATES FROM 1972 TO 1995 : HOW TO COMPENSATE FOR OBSOLETE NORMS

Flynn used data covering 1932 to 1972 to put U.S. gains at about 0.300 IQ points per year. For post-1972, comparison of WISC–R versus WISC–III, particularly the data of Zimmerman and Woo-Sam, gives a rate of 0.312. However, comparison of WAIS–R versus WAIS–III shows that the current rate may be as low as 0 171 It is hypothesized that the discrepancy may be due to sampling error and it is suggested that post-1972 US gains be put at about 0.25 points per year.

Black Americans Reduce the Racial IQ Gap Evidence From Standardization Samples

It is often asserted that Black Americans have made no IQ gains on White Americans. Until recently, there have been no adequate data to measure trends in Black IQ. We analyzed data from nine standardization samples for four major tests of cognitive ability. These data suggest that Blacks gained 4 to 7 IQ points on non-Hispanic Whites between 1972 and 2002. Gains have been fairly uniform across the entire range of Black cognitive ability.

TETHERING THE ELEPHANT Capital Cases, IQ, and the Flynn Effect

Capital offenders cannot be executed if they are mentally retarded. Therefore, the IQ scores of offenders are important, and the U.S. 4th Circuit Court of Appeals has held that the Flynn effect is relevant to interpreting their IQ scores. The Flynn effect (IQ gains over time) means that different IQ tests will give different scores purely as a result of when the tests were normed. Because execution must not be a random result of what test defendants take, a formula is provided to convert IQ scores to a common metric: the norms current at the time the test was taken. The formula also includes a correction based on evidence that the Wechsler Adult Intelligence Scale—Third Edition inflates IQs because of sampling error. Given the inevitability that opposing experts will offer conflicting diagnoses, IQ scores merit special attention in capital cases.

The WAIS-III and WAIS-IV: Daubert Motions Favor the Certainly False over the Approximately True

Daubert motions oppose adjusting IQ scores. They argue that the rate of IQ gains over time (the Flynn Effect) cannot be set at 0.3 points per year with scientific exactitude; therefore, the adjustment formula that rate implies is inadmissible in capital cases. This ignores the fact that there is universal agreement in the scientific community that there have been substantial gains and that, therefore, the worst possible option is to simply leave inflated IQ scores unadjusted. That would undermine equity entirely. New data from the WAIS-IV are included in a meta-analysis of 14 combinations of Wechsler and Binet IQ tests. The overall average is a rate of 0.311 points per year; the average within Wechsler tests is 0.299 point per year. A new estimate of the extent to which the WAIS-III inflated IQs, even at the time it was normed, yields 1.65 points (rather than 2.34 points). However, two new studies comparing the WAIS-III to the Woodcock-Johnson III and the Kaufman Adolescent and Adult Intelligence Scale give huge estimates. It is recommended that WAIS-III scores be set aside and subjects tested on the WAIS-IV and the Stanford-Binet 5.

ISRAELI MILITARY IQ TESTS: GENDER DIFFERENCES SMALL; IQ GAINS LARGE

From 1971 to 1984, the Israeli Defence Forces administered two tests unaltered that qualify as IQ tests. These were the Matrices and the Instructions tests. The former is an adaptation of Ravens Progressive Matrices, similar to the original in that there are clusters with progressive difficulty and an escalation of difficulty throughout the test. The raw score range is from 4 to 35. The Instructions test is adapted from the old US Army Alpha Instructions Test and is described as an Otis-type verbal test. It includes 21 open-ended instructions. Typical items: write the last letter of the word which is the opposite of black; write the third letter of the largest word among the following four words; find the word beginning and ending with the same letter and write that letter. There are similar questions using numbers rather than letters. Both tests are timed, and most subjects do not complete either. There is no penalty for wrong answers (Col. Moshe Even-Chen, personal communication, 14 March 1990; Gal, 1986, pp. 79 and 95; Judy Goldenberg, personal communications, 4 March 1991 and 25 April 1993).

American IQ Gains From 1932 to 2002: The WISC Subtests and Educational Progress

Recent data from 12 pairs of tests representing eight standardization samples show that American IQ gains have occurred at a rate of 0.308 points per year from 1972 to 2002. Linked with earlier IQ gains, Americans have gained about 22 points over the 70 years between 1932 and 2002. Comparing the new WISC-IV (2002) and the old WISC-III (1989) shows a difference of only 2.5 points. However, they have only five subtests in common when full scale IQ is calculated. If one simulates a comparison of the WISC-III and WISC-IV standardization samples on the 10 subtests of the WISC-III, IQ gains over the intervening 12.75 years were no less than 3.83 points, yielding a minimum estimate of 0.300 points per year. Finally, WISC subtest trends taken in conjunction with “the Nations Report Card” (NAEP test trends) provide a fascinating picture of the evolution of cognitive skills in America over the last two generations.

Requiem for nutrition as the cause of IQ gains: Raven's gains in Britain 1938-2008

The hypothesis that enhanced nutrition is mainly responsible for massive IQ gains over time borrows plausibility from the height gains of the 20th century. However, evidence shows that the two trends are largely independent. A detailed analysis of IQ trends on the Ravens Progressive Matrices tests in Britain dramatizes the poverty of the nutrition hypothesis. A multiple factor hypothesis that operates on three levels is offered as an alternative instrument of causal explanation. The Ravens data show that over the 65 years from circa 1942 to the present, taking ages 5-15 together, British school children have gained 14 IQ points for a rate of 0.216 points per year. However, since 1979, gains have declined with age and between the ages of 12-13 and 14-15, small gains turn into small losses. This is confirmed by Piagetian data and poses the possibility that the cognitive demands of teen-age subculture have been stagnant over perhaps the last 30 years.