At the end of the 20th century, a trend of increasing IQ test scores was detected worldwide when comparing successive generations. This phenomenon is known as the Flynn effect and is especially important in populations of low socioeconomic status.

However, the increases in IQ due to the Flynn effect have recently been reduced in rich countries, to the extent that other factors have overcome it, making the current trend in these places towards a decrease in average intelligence.

What is the Flynn effect?

The researcher James Robert Flynn (1934-) has defended during his professional career the fact that intelligence depends largely on environmental factors, which make it unnecessary to resort to inter-group explanations, such as the genetic superiority of certain social groups.

The term “Flynn effect” was coined by Richard Hernstein and Charles Murray in the book The Bell Curve (1994). These authors used it to describe the increase in IQ that occurs with generation changes , a phenomenon that has been detected in many parts of the world and that Flynn helped to spread.

The Flynn effect occurs on fluid, crystallized, spatial and global IQ, but is particularly notable in fluid IQ scores. In contrast to crystallised intelligence, which depends on experience, fluid intelligence is defined as the ability to solve new problems and is mainly attributed to biological factors.

Several studies and meta-analyses conducted worldwide confirmed the cross-cultural nature of the Flynn effect. However, it seems to occur almost exclusively in populations of low socioeconomic status , which most likely indicates that it is related to environmental factors.

The magnitude of the Flynn effect has also diminished over time, at least in rich countries. In addition to this, other phenomena have an influence on the fact that at present the global trend has been reversed and is now negative ; we will talk about this later.

Explanations of this phenomenon

Since the detected increases in intelligence have occurred too rapidly (sometimes up to 10 IQ points in 30 years) to be due to genetic variations, the proposed explanations for the Flynn effect focus primarily on the environment .


1. Improvement of schooling

Some authors have proposed that the Flynn effect is simply due to increased literacy rates, which are associated with improved IQ. On the other hand, access to high quality schooling, especially for children from low socioeconomic backgrounds, may also explain part of this phenomenon.

2. Compensation of nutritional deficits

Nutritional deficits interfere with the physical development of children, and therefore also with their cognitive development. Where children’s nutrition is inadequate, as was the case in most parts of the world a century ago or in many African countries today, IQ scores are generally lower.

It is important to note that these effects overlap with educational improvements from a certain age. In any case, it is believed that nutrition may be more relevant to intellectual development at very early stages of life.

3. Advances in medicine

Like the improvement in nutritional conditions, medical progress has enabled the healthy development of many people. According to some studies it is particularly important to reduce the number of infectious diseases , as well as their severity; this type of alteration can affect the brain if not treated properly.

4. Enrichment of the environment

Flynn himself defended in his book “What is intelligence?” (2007) that recent changes in society have increased the abstract reasoning capacity of the world’s population. These changes can be mainly technological or social.

Among the relevant factors Flynn highlights the familiarization with new technologies , which can be stimulating for the brain, the increase in academic and work demands and the decrease in the number of children per family, which would allow an improvement in the attention and care that the children receive.

5. Familiarity with IQ tests

In addition to the popularization of IQ tests, this factor is related to increased literacy rates and improved formal education. Schooling enhances the capacity for abstract thinking and therefore allows for higher scores on the instruments that measure intelligence.

In the same vein, the test format has spread significantly over the last few decades as a form of educational testing, including tests with verbal and mathematical items very similar to some IQ tests. This may also have influenced familiarity with this type of test.

Are we getting smarter?

Although the Flynn effect is still significant at low socio-economic levels and in poor countries, studies conducted in recent decades confirm that the influence of this phenomenon is diminishing globally. This means that the average IQ level is currently tending to fall , even if the Flynn effect remains.

According to various investigations, the Flynn effect has been overcome by other factors that favour a reduction in the average IQ in countries such as the United Kingdom, Norway, Denmark or Australia. Experts also predict that this decline will continue at least for the rest of the 21st century in Europe and the United States, if the current trend continues.

However, the increase in intelligence is expected to continue in regions where the needs of the population are less well met, such as Latin America, East Asia, the Arab countries, Africa and India.

The exact causes of this phenomenon could not be determined at this stage. There are those who relate it to the arrival of immigrants from countries with a lower average IQ, but the research does not support this hypothesis. On a historical level, the decrease in intelligence has been attributed to the fact that persons with a higher IQ tend to have fewer children .