Can Intelligence Grow? Exploring the Science of Brain Development

•21 Oct 2025
Can Intelligence Grow? Exploring the Science of Brain Development
Intelligence often seems like a fixed trait; something people are either born with or without. However, modern science paints a different picture. Evidence from neuroscience, developmental psychology, and longitudinal studies suggests that intelligence can change over time. In this article, we will explore what intelligence is, how and when it can grow, the role of assessments like the Stanford Binet IQ test, and what you can do to support cognitive development. We’ll also clarify the difference between casual IQ quizzes, professional online IQ test options and formal IQ tests for valid measurement.

 

What is Intelligence?

Intelligence refers broadly to our capacities to reason, learn, solve problems, and adapt to new situations. Psychologists often divide intelligence into several components: fluid reasoning (solving novel problems), crystallized knowledge (what we have learned), working memory (holding information in mind), processing speed, and visual-spatial skills, among others.

A clear way to measure these components is through standardized assessments. The Stanford Binet Intelligence Scale is one of the longstanding tests designed to measure many of those capacities in a reliable way. Other tests exist too, but what matters in measurement is validity (does the test measure what it claims?), reliability (do you get consistent results?), and standardization (test norms).

A professional IQ test, when administered correctly, yields results that can give a trustworthy estimate of one’s intelligence. By contrast, many IQ tests online or free quizzes are more for fun; they vary in quality and may not measure full scale intellectual functioning.

 

Read more about how you can spot a professional IQ test

 

Neuroplasticity: The Brain’s Power to Change

One of the biggest discoveries of modern neuroscience is that the brain remains adaptable, or “plastic,” well into adulthood. This concept is called neuroplasticity. It means the brain can change its structure and function in response to experience, learning, environment, and sometimes injury.

 

Some of the key findings about neuroplasticity include:

  • Morphological and connectivity changes: Training, education, and enriched environments cause changes in how neurons connect, how many synapses there are, and how networks in the brain are structured.
  • Functional changes: Brain imaging (e.g., MRI) shows that the brain areas activated during tasks can shift (e.g. less effort required over time or increased efficiency) after training or practice.
  • Age matters, but plasticity doesn’t disappear: Plasticity is strongest during childhood and adolescence, but adults still show measurable changes with the right interventions.

 

Because of neuroplasticity, intelligence is not entirely fixed. While some aspects are heavily influenced by genetics, many others can improve with experience, training, and the right environment.

What Factors Influence Intelligence Across the Lifespan

Understanding when and how intelligence can grow means looking at the interplay between biology, environment, and individual behaviors. Some of the most important factors include:

 

  1. Genetics and early development: Twin studies and genetic research show that a substantial part of intelligence is inherited, but the expression of genetic potential depends heavily on environment.
  2. Nutrition, health, and early stimulation: Early in life, proper nutrition, pre- and postnatal health, and cognitive stimulation from caregivers (reading, talking, playing) lay foundations for later cognitive growth.
  3. Lifelong learning and environment: Novel experiences, social interaction, challenging tasks, and exposure to new or complex environments help maintain and even increase certain cognitive abilities. For example, learning a second language, practicing music, or engaging in mentally demanding hobbies are often cited.
  4. Lifestyle: sleep, exercise, stress. Physical exercise has been linked to increased neurogenesis (birth of new neurons) and improved connectivity in brain regions involved in memory and reasoning. Sleep is crucial for consolidating learning. Prolonged stress tends to impair brain function.

 

Measuring Intelligence: What Role Do IQ Tests Play?

To see growth, you need reliable ways to measure intelligence. This is where assessments like the Stanford Binet IQ test and other professional tests come in.

Types of IQ Testing

  • Formal IQ tests: Administered by a trained psychologist, following standard procedures. These are carefully normed and validated..
  • Professional Online IQ tests: High-quality digital tools that are research-backed and based on formal IQ tests, like the Stanford-Binet Online IQ test.
  • Casual online quizzes: Informal quizzes that partly mimic elements of professional tests, but often lack standardization, validation, and consistent reliability.

Why measurement matters

  1. Baselines: You can’t measure growth if you don’t have any reliable baseline. A professional test gives you that.
  2. Identifying strengths & weaknesses: For example, someone might have strong verbal reasoning but weaker working memory; test results can point that out.
  3. Tracking change: Re-testing (with proper intervals and care to avoid test practice effects) helps see whether interventions (education, training, lifestyle) have had effect.

The Stanford Binet Intelligence Scale

The Stanford-Binet Intelligence Scale is one of the oldest and most widely recognized professional IQ tests, with origins in the early 20th century and multiple revisions since. It measures several cognitive domains, including fluid reasoning, knowledge, quantitative reasoning, visual-spatial processing, and working memory, and it is normed across a wide age range.

It’s important to clarify, however, that our online version of the Stanford Binet IQ test is derived from the actual scale and is designed to give individuals practice and insight into their cognitive profile, but because it is not proctored, standardized, or administered by a licensed psychologist, it is not considered an official or professionally recognized IQ test.

In other words, the professional Stanford-Binet assessment remains the gold standard for formal evaluation in educational or clinical settings, while the online version serves as an accessible tool for personal exploration and self-awareness.

Thus, when someone refers to the Stanford Binet IQ test, they mean a well-established, professional IQ test that gives a detailed profile of cognitive abilities. 

 

Learn more about the history and evolution of IQ assessments

Take the test now to see where you stand

 

How Much Growth Is Possible And When

Based on existing research, there are some patterns about when intelligence tends to grow, how much, and under what conditions:

 

  • Early childhood (0-5 years): Rapid growth occurs; neural connections are formed quickly; early stimulation and health have large effects.
  • Childhood and adolescence: Continued growth. Schooling, training, and learning new skills have strong effects; neural plasticity is relatively high.
  • Young adulthood: Gains are harder, but improvements are possible, especially in areas like reasoning and processing speed, with targeted training and enriched environments.
  • Later adulthood: More limited, but cognitive decline is not inevitable. With exercise, mental engagement, social interaction, some abilities can be maintained or modestly improved.

 

Quantifying growth is harder. Some studies show increases of a few IQ points via intervention. Ultimately, improvements often depend on repeated, long-term training rather than short-term efforts.

 

Limitations, Caveats, and Misconceptions

 

To keep expectations realistic, it is important to understand what intelligence growth isn’t and what it might not achieve.

 

  • Test practice effects: If you take the same test (or a very similar one) again, you might do better simply because you are familiar with its format and not necessarily because your underlying reasoning ability improved.
  • Transfer issues: Training in one cognitive domain doesn’t always lead to improvements in unrelated domains. For example, improving working memory doesn’t always lead to sharper verbal reasoning unless the training specifically targets that.
  • Plateau: After initial improvements, people often hit plateaus where further gains become harder to achieve without more intense or different kinds of training.
  • Genetic limits and individual differences: Some aspects of intelligence have strong genetic contributions. Also, baseline conditions (e.g. early childhood environment) limit how much growth is possible for some individuals.

 

Putting It All Together: Growth and Measurement

 

So what do we know when we combine all this? Intelligence is neither entirely fixed nor limitlessly adaptable. Instead, it exists on a spectrum: with biological constraints, but considerable room for growth, especially early in life and under favorable conditions. The tools of measurement help us map where an individual is, what their strengths are, and where growth is possible.

 

Practical Advice: How to Support and Track Intelligence Growth

 

Here are some evidence-backed strategies you can apply, whether for yourself, a child, or a student:

 

  1. Invest in early childhood enrichment: Quality early education, lots of language exposure, play, caregiver interaction.
  2. Engage in learning new skills: Reading, math, music, language, arts: the novelty and challenge matter.
  3. Maintain a healthy lifestyle: Good nutrition, sleep, stress management, regular physical exercise.
  4. Use valid measurement tools: When possible, use a professional IQ test tool to establish a baseline, then periodically reassess to track real changes (allowing for practice effects and test reliability).
  5. Diversify cognitive stimulation: Mix different types of tasks (verbal, quantitative, visual-spatial) rather than focusing narrowly on one.

 

Conclusion

The weight of scientific evidence suggests that intelligence is not a static, unchangeable trait. From early childhood through adulthood, under the right conditions, the brain can adapt, learn, and in many cases improve. While no magic pill will dramatically raise IQ overnight, consistent learning, rich environments, proper rest and health, and using professional tools for measurement can lead to meaningful growth.

 

 

If you're curious about your own cognitive profile, consider taking a well-validated online IQ test like the Stanford-Binet IQ Test. These assessments can show where you are today, and guide efforts to grow.

 

Explore the Stanford Binet IQ Test online to gain research-based insights into your abilities.

 

References:

  1. Brans, R. G. H., Kahn, R. S., Schnack, H. G., van Baal, G. C. M., Posthuma, D., van Haren, N. E. M., Lepage, C., Lerch, J. P., Collins, D. L., Evans, A. C., Boomsma, D. I., & Hulshoff Pol, H. E. (2010). Brain plasticity and intellectual ability are influenced by shared genes. Journal of Neuroscience, 30(16), 5519–5524. https://pmc.ncbi.nlm.nih.gov/articles/PMC6632359/
  2. Bryck, R. L., & Fisher, P. A. (2012). Training the brain: Practical applications of neural plasticity from the intersection of cognitive neuroscience, developmental psychology, and prevention science. American Psychologist, 67(2), 87–100. https://pubmed.ncbi.nlm.nih.gov/21787037/
  3. Carroll, J. B. (1993). Human cognitive abilities: A survey of factor-analytic studies. Cambridge University Press. https://www.cambridge.org/core/books/human-cognitive-abilities/F83D5EADF14A453F6350FF3DD39631C8
  4. Cherry, K. (2023, May 17). What is brain plasticity? Definition and how it works. Verywell Mind. https://www.verywellmind.com/what-is-brain-plasticity-2794886
  5. Deary, I. J., Whalley, L. J., & Starr, J. M. (2009). A lifetime of intelligence: Follow-up studies of the Scottish mental surveys of 1932 and 1947. American Psychological Association. https://doi.org/10.1037/11857-000
  6. deLeyer-Tiarks, J. M. (2024). Assessment of human intelligence—The state of the art in the 2020s: Introduction to the special issue. Journal of Intelligence, 12(10), 192. https://pmc.ncbi.nlm.nih.gov/articles/PMC11355244/
  7. Gottfredson, L. S. (1997). Mainstream science on intelligence: An editorial with 52 signatories, history, and bibliography. Intelligence, 24(1), 13–23. https://www1.udel.edu/educ/gottfredson/reprints/1997mainstream.pdf
  8. Hausknecht, J. P., Halpert, J. A., Di Paolo, N. T., & Moriarty Gerrard, M. O. (2007). Retesting in selection: a meta-analysis of coaching and practice effects for tests of cognitive ability. The Journal of applied psychology, 92(2), 373–385. https://doi.org/10.1037/0021-9010.92.2.373
  9. Jaeggi, S.M., Buschkuehl, M., Shah, P. et al. The role of individual differences in cognitive training and transfer. Mem Cogn 42, 464–480 (2014). https://doi.org/10.3758/s13421-013-0364-z
  10. Liu, P. Z., & Nusslock, R. (2018). Exercise-mediated neurogenesis in the hippocampus via BDNF. Frontiers in Neuroscience, 12, 52. https://pmc.ncbi.nlm.nih.gov/articles/PMC5808288/
  11. Nithianantharajah, J., & Hannan, A. J. (2006). Enriched environments, experience-dependent plasticity and disorders of the nervous system. Nature Reviews Neuroscience, 7(9), 697–709. https://pmc.ncbi.nlm.nih.gov/articles/PMC8494941/
  12. Plomin, R., Deary, I. Genetics and intelligence differences: five special findings. Mol Psychiatry 20, 98–108 (2015). https://doi.org/10.1038/mp.2014.105
  13. Prado, E. L., & Dewey, K. G. (2014). Nutrition and brain development in early life. Nutrition Reviews, 72(4), 267–284. https://academic.oup.com/nutritionreviews/article/72/4/267/1859597
  14. Sala, G., & Gobet, F. (2019). Cognitive Training Does Not Enhance General Cognition. Trends in cognitive sciences, 23(1), 9–20. https://doi.org/10.1016/j.tics.2018.10.004
  15. Stankov, L., & Lee, J. (2020). We Can Boost IQ: Revisiting Kvashchev's Experiment. Journal of Intelligence, 8(4), 41. https://doi.org/10.3390/jintelligence8040041
  16. Tymofiyeva, O., & Gaschler, R. (2021). Training-induced neural plasticity in youth: A systematic review of structural and functional MRI evidence. Frontiers in Human Neuroscience, 14, 497245. https://pubmed.ncbi.nlm.nih.gov/33536885/