Does experience increase intelligence? Study shows it’s not permanent

children at school
Children at school - Photo by: Lucélia Ribeiro
One of the most disputed questions about human intelligence is the “nature vs nurture” debate, an argument that still splits the scientific community in two. Since we increased our understanding of how children and babies learn and perceive the outside world, we learned how significantly environmental interventions can affect children mental and psychological development. Nonetheless, a complete understanding and quantitative evaluation on how much experience and education may increase a human being’s IQ is still slipping from our grasp. A new study by a psychologist at the University of California, Santa Barbara, however, may shed some light on the relevance of outside influences compared to inherited traits in the difficult journey towards increasing a child’s intelligence.
The study led by the postdoctoral scholar John Protzko, a psychologist from the META (Memory, Emotion, Thought, Awareness) Lab,  was (appropriately) published in the journal Intelligence. The researcher reviewed data from 985 children from the Infant Health and Development Program (IHDP). This program included low birth weight (LBW), as well as children of low socioeconomic status, affected by risk factors during pregnancy or birth or at risk for developmental delay or disorder. Children in the program received home visits, parent support groups, and a systematic educational program developed to enhance their cognitive, behavioral, and health status and prevent later developmental problems.

What’s the answer to the “nature vs. nurture” debate?

Dr. Protzko found that LBW babies received intense stimulations during the first three years of their lives thanks to development interventions they received. Their intelligence was positively affected, proving that environmental factors did, in fact, increase their cognitive capabilities. Children’s intelligence was repeatedly measured with the Stanford-Binet Intelligence Scales, showing that at age three most subjects included in the program performed better than the average. However, at age five and eight, as soon as the babies left the program, the improvements slowly disappeared suggesting that the environmental effects are not permanent. Dr. Protzko explained this phenomenon with the “fade out effect” theory, that describes intelligence as a reactionary trait that slowly disappears as soon as the subject is not exposed to a cognitively demanding environment anymore. In his quantitative analysis, the psychologist tries may have provided sufficient evidence to demonstrate that without continuity, even intensive intervention’s effect usually last for no more than two years.
Protzko even postulated that previous studies that took for granted the intelligence causality may also be wrong. According to the intelligence causality theory, increasing one own’s cognitive ability at one age will improve cleverness and acumen at subsequent ages. This theory provided the scientific basis to explain, for example, that if a subject is more intelligent than the average when he’s 16 years old, he will possess superior cognitive skills even when he will be an adult. Evidence provided in Protzko’s studies, however, may suggest a very different outcome. Similarly to other traits such as agility, coordination or strength, intelligence adapts itself when the environmental demand is higher than usual. In a likely fashion to what happens to muscle memory, cognitive abilities will progressively fade out as soon as they’re not trained out and may even return to its original levels, at least in children. Protzko explained that to understand whether the fade out effect applies to other demographics such as adults, adolescents and elderly, a longer follow-up period of three or more years may be required.
Article was written by Dr. Claudio Butticè, PharmD.


  1. Julie Cohen. The Fadeout Effect. The UC Santa Barbara Current. December 3, 2015.
  2. Craig T. Ramey, PhD, Donna M. Bryant, PhD, Joseph Sparling, PhD & Barbara H. Wasik, PhD. The Infant Health and Development Program – An Early Intervention Program for Low Birth Weight Premature Infants. Sociometrics. (Accessed March 2016)
  3. C. Butticè. How much the environment can affect our IQ? New study sheds light. Digital Journal. March, 15, 2016.
  4. John Protzko. Does the raising IQ-raising g distinction explain the fadeout effect? Intelligence, Volume 56, May–June 2016, Pages 65–71. doi:10.1016/j.intell.2016.02.008