Average IQ: What is the Average Intelligence Quotient and What Does it Mean?
Everything you need to know about average IQ, the distribution curve, what a score really means, its limitations — and how to understand intelligence beyond a number.
What is IQ? Origins and Definition
The intelligence quotient (IQ) is a standardized measure aimed at assessing an individual's general cognitive abilities compared to those of a reference group of the same age. It was developed in the early 20th century by the French psychologist Alfred Binet, commissioned by the government to identify children needing special educational support. Binet's measure was based on "mental age" — if an 8-year-old child succeeded in tasks typically passed by 10-year-old children, their mental age was considered to be 10 years.
The initial formula for IQ (mental age / chronological age × 100) was replaced in the 1960s by "deviation IQ" — the current score, which no longer compares to a mental age but positions an individual's result relative to the distribution of results of their age group. It is this deviation IQ that all modern tests measure.
How is IQ set at 100?
The average IQ is set at 100 by construction — it is a statistical convention, not a biological reality. During the standardization (or "normalization") of an IQ test, the designers administer it to a large representative sample of the population, calculate the median performance of each age group, and assign it the score of 100. The scores of other individuals are then positioned relative to this median according to a normal distribution (bell curve), with a standard deviation of 15 points.
📊 The normal distribution of IQ in the population
IQ scores follow a normal distribution (bell curve) with an average of 100 and a standard deviation of 15. This means that :
• 68 % of the population is between 85 and 115 (±1 standard deviation)
• 95 % of the population is between 70 and 130 (±2 standard deviations)
• 99.7 % of the population is between 55 and 145 (±3 standard deviations)
• Only 2.2 % of the population has an IQ above 130
• Only 2.2 % of the population has an IQ below 70
The distribution of IQ scores: ranges and meanings
📊 Distribution of IQ scores in the population
Intellectual disability
~2.2 %
Below average
~13.6 %
Normal (average)
~68 %
Above average
~13.6 %
High intellectual potential (HPI)
~2.2 %
Exception (genius)
< 0.1 %
| IQ Range | Qualification | % of the population | Practical implications |
|---|---|---|---|
| Less than 70 | Intellectual disability (mild to severe) | ~2.2 % | Significant difficulties in daily living activities; need for support |
| 70–84 | Below average | ~13.6 % | Slower learning; may succeed with appropriate support |
| 85–115 | Normal / Average | ~68 % | Adapted functioning in the vast majority of daily and professional situations |
| 116–129 | Above average / Superior | ~13.6 % | Quick learning; success in demanding higher education |
| 130–144 | Very superior / HPI | ~2.2 % | High intellectual potential; may exhibit specific characteristics (hypersensitivity, school boredom…) |
| 145 and above | Exception | < 0.1 % | Exceptional — represents less than 1 person in 1,000 |
What does IQ actually measure?
Modern IQ tests — such as the WAIS-IV (Wechsler Adult Intelligence Scale) for adults or the WISC-V for children — do not measure a single ability, but a profile of several cognitive abilities grouped into factors.
The main factors measured by modern IQ tests
Vocabulary, verbal reasoning, general knowledge
This factor assesses the ability to understand and use language accurately, to reason with verbal concepts, and to mobilize general cultural knowledge. It is closely related to crystallized intelligence — accumulated knowledge — and tends to be stable or progress with age and education.
Non-verbal logical reasoning, matrices, patterns
This factor evaluates the ability to reason with visual information and patterns, to identify rules in sequences, and to solve new problems without relying on acquired knowledge. It is the measure closest to fluid intelligence — and the one that declines most sharply with age.
Retaining and manipulating information in real time
Memorizing a sequence of numbers and repeating it backward, mentally performing an arithmetic operation while retaining other information — this factor evaluates the ability to maintain and manipulate information in short-term memory. It is closely related to performance in academic and professional learning.
Speed and efficiency of cognitive processing
This factor evaluates how quickly the brain processes simple information — copying symbols, identifying similarities in a series. It is one of the first to decline with age, but also one of the most sensitive to fatigue and acute stress.
The Flynn effect: why does the average IQ increase?
One of the most fascinating — and most discussed — phenomena in psychometrics is what New Zealand researcher James Flynn documented in the 1980s: the average IQ increases by about 3 points per decade since tests have existed. This phenomenon, called the "Flynn effect," is robust and has been observed in many countries.
What explains it? Not genetic change (too slow to produce this effect in a few decades). The most serious hypotheses point to: better nutrition during childhood (especially in micronutrients), reduced exposure to neurological toxins (like lead), longer and more intensive schooling, and — probably the most important factor — increasing familiarity with abstract thinking and reasoning modes required by IQ tests.
💡 What the Flynn effect teaches us about IQ
If the average IQ increases by 3 points per decade, it means that a score of 100 in 2024 does not correspond exactly to the same level of performance as a score of 100 in 1980. Tests are regularly re-normed to keep the average at 100. This also illustrates that performance on IQ tests is influenced by the environment — schooling, nutrition, cognitive stimulation — and not just by "innate" abilities.
Can IQ increase or decrease?
This is one of the most frequently asked questions — and the answer is nuanced. IQ is relatively stable in adulthood under normal conditions. But "relatively stable" does not mean "completely fixed." Factors can modify performance on IQ tests:
✔ Factors that can affect IQ test results
- Education and intellectual stimulation: quality schooling and environments rich in cognitive stimulation improve cognitive performance
- Health status: neurological diseases, nutritional deficiencies, sleep disorders, and chronic stress degrade cognitive performance
- Aging: some components (fluid reasoning, processing speed) decline with age, while others (verbal comprehension) remain stable or even improve
- Specific test training: familiarizing oneself with test formats can improve scores by 5 to 15 points — without necessarily improving underlying cognitive abilities
- Motivation and emotional state on test day: anxiety, fatigue, or lack of motivation can significantly depress scores
Can cognitive training improve IQ?
The research on this point is nuanced. Cognitive training programs (notably intensive working memory training) have shown improvements on trained tasks, and sometimes transfers to related tasks. More recent studies have found modest effects on components of fluid reasoning with intensive and prolonged programs. The effect on "IQ" in the broad sense remains debated — but the improvement of specific cognitive functions (memory, attention, executive functions) is well documented.
DYNSEO offers cognitive stimulation applications tailored to each age to support this training: CLINT for adults, COCO for children aged 5 to 10, and the AI Coach for personalized support.
The limits of IQ: what it does not measure
IQ is a powerful and well-validated psychometric tool for what it measures. But it is crucial to understand its limits to avoid overinterpretation.
IQ does not measure all forms of intelligence
Howard Gardner proposed in 1983 his theory of multiple intelligences — musical, bodily-kinesthetic, interpersonal, intrapersonal, naturalistic — which are not or are poorly measured by standard IQ tests. Robert Sternberg introduced the notion of practical intelligence (adaptive know-how in the real world) and creative intelligence. These theories are discussed in cognitive sciences, but they remind us that IQ captures only a part of human abilities.
IQ is not destiny
An IQ score does not predict individual success or happiness. Factors such as perseverance, curiosity, creativity, emotional intelligence, socioeconomic conditions, the quality of education received, luck, and health play an equally important role in life trajectories. Studies show that "deliberate practice" (sustained effort over the long term) often predicts success better than IQ.
IQ can be affected by cultural biases
IQ tests were developed in specific cultural contexts, and some items may favor people familiar with certain cultural, linguistic, or educational codes. Significant efforts have been made to reduce these biases in modern versions of the tests, but they are not completely eliminated. A low score does not necessarily mean limited cognitive abilities.
Average IQ and context: international comparisons
Studies have attempted to compare average IQs between countries and regions. These comparisons are delicate — tests are not always equivalent from one cultural context to another, testing conditions vary, and sample selection biases are significant. Available data suggest significant variations between countries, largely correlated with the level of economic development, the quality of educational systems, access to healthcare, and exposure to toxic factors such as lead. What is clear: the differences observed between groups are mostly environmental in nature, not genetic.
IQ and High Intellectual Potential (HIP)
An IQ of 130 or higher conventionally defines High Intellectual Potential (HIP) — which represents about 2 to 2.5% of the population. People with HIP may exhibit specific characteristics that go beyond simple cognitive performance: tree-like thinking, sensory hyperesthesia, emotional hypersensitivity, perfectionism, feelings of social mismatch. HIP is not without challenges: school boredom, difficulty finding peers of similar level, and sometimes associated psychological distress are realities for some of these individuals.
"A high IQ is like a powerful engine — it says nothing about the direction one is taking, nor about how one drives."
Beyond IQ: how to assess your cognitive profile?
Rather than focusing on a single number, the most useful approach is to explore your cognitive profile — the specific strengths and weaknesses in different cognitive areas. A cognitive profile can reveal excellent working memory associated with average processing speed, or very high verbal comprehension associated with less developed executive functions.
🧪 Explore your cognitive profile with DYNSEO
DYNSEO offers several online cognitive tests to assess different dimensions of your cognitive abilities — well beyond a simple overall score:
• Mental age test — estimate the cognitive age of your brain
• Executive functions test — planning, flexibility, inhibition
• Memory test — assess your memory capabilities
• All DYNSEO cognitive tests
For professionals supporting children or adults in educational, therapeutic, or educational settings, the DYNSEO skills tracking table allows for documenting the evolution of cognitive abilities over time — a valuable complement to one-time assessments.
Is an online IQ test reliable?
Public online IQ tests are generally not rigorously standardized and cannot replace a professional psychometric evaluation. They can provide an approximate indication, but with a significant margin of error. A validated IQ test (WAIS, Stanford-Binet) is always taken in the presence of a professional under standardized conditions.
Can a child have a measured IQ? From what age?
Yes. Validated IQ tests exist for children from the age of 2 and a half (WPPSI for young children, WISC-V from 6 years old). These assessments are conducted by neuropsychologists or specialized psychologists, most often in the context of a school evaluation, suspicion of giftedness, or assessment of learning disorders.
What is the link between IQ and neurodevelopmental disorders such as ADHD or dyslexia?
Neurodevelopmental disorders (ADHD, dyslexia, dyscalculia, autism) are not defined by a low IQ. Individuals with ADHD or dyslexia can have a very high IQ. What characterizes these disorders is a disharmony in the cognitive profile — marked strengths and difficulties in specific areas, often associated with very variable scores between the different sub-tests of an IQ assessment. This is why analyzing the intra-individual profile is often more important than the overall score.
Conclusion: IQ, a tool among others to understand intelligence
IQ is a useful and scientifically validated indicator for certain questions — particularly in clinical settings, special education, and research on cognitive abilities. The average IQ of 100 is a statistical convention that allows situating an individual relative to their age group, but it says little about their value, potential for development, or ability to thrive and succeed in life.
Intelligence is a multidimensional phenomenon that cannot be reduced to a score. Exploring one's cognitive profile — specific strengths, areas for improvement, characteristics — is a richer and more useful approach than trying to assign a number to one's brain. For this, discover our cognitive tests and our tracking tools.
