Children’s IQ and Fade-Out Effect

People are not born with the same intellectual abilities. This is a simple fact of life, and there is nothing surprising about it. After all, we are also born with different height, physical strength, color of skin and so on. However, some characteristics of our body, such as muscular strength and endurance, are modifiable and can be trained. Scientists long argued that intellectual abilities, as reflected by the IQ level, can be trained too. But do we have any conclusive proofs to confirm this theory?

It appears that the proofs for the opposite have just emerged, in the form of confirmed “fade-out” effect in children.

The uncomfortable fact of life is that social inequality is linked with the intellectual inequality. Some people argue that cleverer people simply achieve more and thus form “upper class”. Others believe that social inequality prevents talented individuals with under-privileged background to fully realize their potential. Arguably, children of the better-off parents are exposed to more stimulating intellectual environment.

One way or another, any interventions that can genuinely improve the level of IQ in children may help these children to build more successful careers and thus, indirectly, address the problem of social inequality.

A number of Western countries do have policies and intervention programs aimed exactly at achieving this goal. A good example is the Head Start Program in the US that provides comprehensive early childhood education, balanced nutrition and proper medical care for children from low-income families. There are similar programs in a number of European countries too.

Many studies have tried to measure the effectiveness of these programs over the years, but failed to reach any clear conclusion. What many of these studies have noticed, however, is a fade-out effect: the IQ level of participants may rise during the participation in the program, but once the intervention is stopped, the IQ level drops. Again, it was not clear how common the fade-out effect is and whether this is a real effect or just a phenomenon caused by using different approaches to the studies or by bias in selecting the participants.

A study published in December 2015 appears to finally confirm the existence of fade-out effect. Meta-analysis of the large set of data involving 39 randomized controlled trials and 7,584 participants demonstrated that statistically significant fade-out effect is clearly visible in this large cohort. The author of this research believes that intelligence can adapt to environmental demands in both directions, i.e. both upwards and downwards.

As such, the finding is not that surprising, even if it is disappointing. After all, physical strength and many other parameters of our physiology do respond to the presence or absence of stimuli or training in exactly the same way. But the exact mechanisms behind the fade-out effect still remain a mistery.

Some researchers argue that the fade-out effect occurs because the gains in intelligence are not real. They say that interventions help in improving the short-term memory but do not train intelligence as such. Some also argue that perceived improvement in intelligence is nothing more that the effect of training aimed at performing better in the IQ tests.

The IQ test itself is viewed with suspicion by many researchers who believe that it is too limited and does not reflect the real level of intelligence. This is because different people demonstrate clear and obvious differences in learning styles. Researchers distinguish several categories of learners by style, including linguistic verbal learner, logical mathematical verbal learner, spatial or visual learner, the bodily learner, musical learner, interpersonal learner, intrapersonal learner and naturalistic learner. The critics point out that IQ testing does not consider all these categories of intelligence.

Unfortunately, we still don’t have a measure of intelligence that could be applied to different learning styles and intelligence types and would be accepted by everyone.

Another dimension of the problem is the changing nature of intelligence with the age. We can confidently assume that the child’s interests are different at different ages. Also, as brain develops, it might be learning and memorizing the information about the environment using different mechanisms. This may also affect the standard intelligence measurements obtained through the use of IQ tests.

Genetic factors underlying intelligence are poorly studied at present time. Also, there is a kind of social taboo on raising this issue. Both researchers and general public accept the fact that extremely high and extremely low levels of intelligence are genetically determined, but the variations in intelligence within the “normal” range are often assumed to be determined by social and environmental, rather than genetic factors. The fact that some people might be cleverer than others simply due to being winners in genetic lottery is unpalatable to many people. This, however, is something to look at seriously and pragmatically.

The confirmation of fade-out effects indirectly points to the substantial role of genetic factors in determination of our basal inborn level of intelligence. It also says that there is a limit to what can be done to improve the intelligence via the existing intervention approaches. Good or bad, this is a world we live in, and it will be better for all of us to accept this fact and think about what else can be done to help the children with lower IQ to achieve the best they can do in life.


Protzko, J. (2015). The environment in raising early intelligence: A meta-analysis of the fadeout effect Intelligence, 53, 202-210 DOI: 10.1016/j.intell.2015.10.006

Tucker-Drob, E., & Bates, T. (2015). Large Cross-National Differences in Gene x Socioeconomic Status Interaction on Intelligence Psychological Science DOI: 10.1177/0956797615612727

Vincent, A., & Ross, D. (2001). Personalize training: determine learning styles, personality types and multiple intelligences online The Learning Organization, 8 (1), 36-43 DOI: 10.1108/09696470110366525

Image via Richard Thornton / Shutterstock.

Viatcheslav Wlassoff, PhD

Viatcheslav Wlassoff, PhD, is a scientific and medical consultant with experience in pharmaceutical and genetic research. He has an extensive publication history on various topics related to medical sciences. He worked at several leading academic institutions around the globe (Cambridge University (UK), University of New South Wales (Australia), National Institute of Genetics (Japan). Dr. Wlassoff runs consulting service specialized on preparation of scientific publications, medical and scientific writing and editing (Scientific Biomedical Consulting Services).
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