Does IQ increase as we get older? Does it decrease? Does it remain the same? Explore the different ways to answer these questions and discover the roles of crystallized and fluid intelligence in this lesson.
Intelligence and Age
Here we have 10-year-old Dave, 30-year-old Dave, 50-year-old Dave and 70-year-old Dave. Which Dave is the most intelligent?
This is a much more complicated question than you might think! Does intelligence increase with age, decrease with age, remain the same, or does it undergo other types of changes? The effect of age on IQ is a controversial topic among researchers. The answer to this question will also depend on how you define intelligence. Is there more than one type of intelligence? Can intelligence truly be measured by a test score?
It has been shown that scores on IQ tests actually decrease with age. This chart shows how scores on Wechsler IQ tests peak between 25 and 29 years old, then decline throughout the rest of adulthood, with a decline becoming more steep after the age of 70. This would mean that 30-year-old Dave is the smartest, right?
Wechsler IQ Test results peak at ages 25-29
For many years, it was accepted that a person's IQ increases until early adulthood and then begins to diminish as they grow older. This idea has been challenged by new theories and research in recent years.
Challenges to Traditional Thought
When information regarding IQ scores and age is examined in a different way, it can be shown that individuals rank in the same order that they did when they took the test at different ages. This means that intelligence remains stable throughout a person's life. In other words, due to age-related changes, older people can perform worse on an intelligence test without it indicating any drop in actual IQ.
This would mean that 10-year-old, 30-year-old, 50-year-old and 70-year-old Dave are actually equally intelligent. Is this really possible? How can a person's IQ score drop, but their intelligence remain stable?
One reason is given in a study that shows physical advantages for younger adults help them to score higher on IQ tests. In other words, manual dexterity and better eyesight help younger adults perform better on IQ tests even though they may not have a higher level of intelligence. It has also been suggested that changes in IQ tests over the years can make for misleading research results. This is because the researchers may not be comparing scores from equal tests.
The Brand hypothesis is another reason that comparisons of IQ at different ages may not be fair. The Brand hypothesis is the idea that a person's attitude and approach to test taking may impact their scores on IQ tests. The Brand hypothesis supports the idea that younger people obtain better scores on timed tests not only because of physical advantages, but also because they're more likely to guess while older people are more likely to attempt to get every test item correct.
Some researchers also feel that it can be deceiving to say intelligence declines with age because there are many types of intelligence. Older people may lose some of their ability to process information, but they gain experiences that increase their understanding.
The majority of researchers believe that IQ remains stable with age but that the components of a person's intelligence change. The changing components of intelligence can usually be described as fluid intelligence and crystallized intelligence. Fluid intelligence is the ability to reason and process information. Crystallized intelligence is the information you gain through experience.
There have been many studies which show that fluid intelligence is expected to decline with age. In contrast, crystallized intelligence actually continues to grow with age as a person has more experience and learns new skills through their life. Many believe that this combination of increase and decrease keeps a person's overall level of intelligence relatively stable with age. In other words, the decrease in fluid intelligence is compensated for by the increase in crystallized intelligence.
It has been shown that IQ scores decrease with age, but this doesn't necessarily mean that intelligence decreases. A decrease in IQ scores with age could be the result of diminished physical abilities, changes in test taking strategies or changes to tests that create misleading research results.
When a group of individuals takes an IQ test at different ages, they will typically rank in the same order at each age. This indicates that intelligence remains stable. These two different results may be due to changes in fluid intelligence and crystallized intelligence. As fluid intelligence decreases with age, crystallized intelligence increases. This allows overall intelligence to remain stable.
After finishing this lesson, you should be able to:
- Understand the misleading results of age and IQ
- Discuss fluid and crystallized intelligence throughout the lifespan