Understanding intelligence across the lifespan
The idea that intelligence is a fixed trait that peaks and then fades is a myth. Scientific research into cognitive development shows that different aspects of intelligence change throughout our lives, sometimes in surprising ways. To understand this, we must first look at the two main components of general intelligence, often referred to as the 'g-factor,' proposed by psychologist Raymond Cattell.
Fluid vs. crystallized intelligence: A tale of two cognitive abilities
Intelligence is not a monolith, but a combination of different abilities. Two major types are:
- Fluid Intelligence (Gf): This is the ability to reason and think flexibly, solve new problems, and process information quickly, independently of previously acquired knowledge. It's the type of intelligence used for puzzles, strategy games, and adapting to new technologies. Fluid intelligence tends to peak in early adulthood, around the 20s, and then gradually decline with age.
- Crystallized Intelligence (Gc): This refers to the accumulation of knowledge, facts, and skills acquired over a lifetime through education, experience, and cultural exposure. This is the intelligence used to solve problems based on past experience and knowledge, such as vocabulary and general knowledge. Unlike fluid intelligence, crystallized intelligence can increase and remain stable throughout much of adulthood, peaking much later in life—sometimes as late as the 60s or 70s.
What the IQ score doesn't tell you
While this distinction is crucial for understanding aging, the typical IQ score can be misleading. This is because standardized IQ tests are age-normalized, meaning your score is compared to the average performance of people in your specific age group. For every age group, the average IQ is set at 100. So, while the raw scores on subtests measuring different abilities will change, your overall IQ score relative to your peers can remain remarkably stable from childhood into late adulthood. A high-ranking 20-year-old will likely remain a high-ranking 90-year-old compared to their age-matched peers, even as both individuals' absolute cognitive abilities have changed.
The role of neuroplasticity in lifelong learning
The brain's ability to change and adapt, known as neuroplasticity, is a powerful counterargument to the idea that intelligence is fixed. Neuroplasticity allows the brain to form new neural connections and pathways in response to new experiences, learning, and environmental stimulation. This process is most robust in youth, but contrary to older beliefs, it continues throughout the entire lifespan.
This is why lifelong learning is so beneficial. Engaging in mentally stimulating activities helps build cognitive reserve, which is the brain's ability to cope with damage or decline. A strong cognitive reserve can help delay the onset of age-related cognitive issues. This is especially important during retirement, when a decrease in mental demands can lead to cognitive decline.
How to maintain a healthy brain as you age
Maintaining your cognitive health is an active process that involves a combination of lifestyle choices. It's never too early or too late to adopt habits that support a sharp, healthy mind.
1. Mental stimulation
- Learn a new skill: Pick up a musical instrument, learn a new language, or take up a new hobby like painting. This forces the brain to create new connections and pathways.
- Play brain games: Puzzles, crosswords, and strategic board games challenge your problem-solving and memory skills.
- Read widely: Reading exposes you to new information and perspectives, strengthening memory, imagination, and other cognitive abilities.
2. Physical exercise
- Aerobic activity: Regular physical exercise increases oxygen and blood flow to the brain, which supports cognitive function and stimulates the release of growth factors that enhance brain connections.
- Combine with mental activity: Studies show that older adults who learned a new skill improved their memory more than those who only socialized, highlighting the importance of combined mental and physical activity.
3. Healthy diet and sleep
- Brain-boosting nutrients: Diets rich in fruits, vegetables, and healthy fats (like the Mediterranean or MIND diet) support brain health.
- Prioritize sleep: Quality sleep is crucial for memory consolidation and for allowing the brain to perform 'housekeeping' duties, such as removing a toxic protein linked to Alzheimer's disease.
4. Social engagement and stress management
- Stay connected: Strong social ties and regular interaction help stimulate the brain, reduce stress, and have been linked to a lower risk of cognitive decline.
- Manage stress: Chronic stress can negatively impact brain function. Mindfulness meditation, deep breathing, and spending time in nature can help reduce cortisol levels and support neuroplasticity.
Comparing intelligence types and aging
| Feature | Fluid Intelligence (Gf) | Crystallized Intelligence (Gc) |
|---|---|---|
| Associated Abilities | Reasoning, problem-solving, abstract thinking, processing speed | Vocabulary, general knowledge, accumulated facts, experience |
| Peak Age | Early adulthood (approx. 20s) | Later adulthood (can increase into 60s or 70s) |
| Age-Related Change | Tends to decline gradually with age, more rapidly after 70 | Tends to remain stable or increase throughout adulthood before a gradual, later decline |
| Impact on IQ Score | Subtests measuring Gf (like Matrix Reasoning) often show age-related decline in raw scores | Subtests measuring Gc (like Vocabulary) show minimal change or improvement in raw scores |
| Can it be trained? | Evidence suggests some aspects can be improved with cognitive training exercises | Primarily developed through ongoing learning and experience |
Conclusion
Instead of asking at what age does IQ stop, a better question is how intelligence evolves over a lifetime. The fixed-intelligence mindset is outdated. Our minds are dynamic, with some abilities growing and others shifting. By understanding the distinction between fluid and crystallized intelligence and embracing lifestyle habits that promote neuroplasticity, we can actively support our cognitive health and ensure a sharper, more engaged mind at any age.
Further reading
For more information on the evolving understanding of intelligence and cognitive aging, the National Institute on Aging (NIA) provides a wealth of research-backed resources.
