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Knowledge baseThe science of intelligence
What researchers have learned about the mind over more than a hundred years, explained simply and with sources: what intelligence is, how it grows, how it is measured and what the theory of multiple intelligences adds.
What intelligence is
What is intelligence?
Why intelligence is so hard to define, how thinkers from Plato to Piaget, Gardner and Sternberg have understood it, and what parents can — and cannot — see in their own child.
Eight myths about intelligence
Do school marks show how intelligent a child is? Do we really use only 10% of our brain? Eight popular beliefs about intelligence — and what scientific research says about them.
History and theories
How the first intelligence tests appeared
From Esquirol and Galton to Binet, Terman and Wechsler: how and why intelligence tests came about, and why their best use is still to help children who need support.
One intelligence or many? From Spearman to the CHC model
Is there one general ability behind all our successes, or several separate ones? From Spearman's general factor to the CHC model: the story of a century-long debate and what it means for parents.
Guilford and creativity: one answer or many?
How a psychologist who selected wartime pilots opened the scientific study of creativity: Guilford's model of the intellect, convergent and divergent thinking, the four stages of a new idea and simple exercises for home and class.
Gardner's theory: what it says and what it does not
Howard Gardner's theory of multiple intelligences in plain words: where it came from, his definition, eight criteria and eight intelligences, common misunderstandings, what critics say and how Zehnhoi Gunogun uses the theory.
Practical intelligence and the Greek mētis
Why some children who struggle with school tests shine at the market, in the workshop or on the pitch: Sternberg's practical intelligence, the Greek idea of mētis, the line between cleverness and wisdom, and how this kind of intelligence grows.
How thinking develops
Piaget: how a child's thinking grows
Jean Piaget showed that children do not simply know less than adults: they think differently. The four periods of development with everyday examples, what later research changed, and how to support thinking at home at ages 2–6, 7–11 and 12–18.
Thinking grows in conversation
Children learn to reason not only from books but by talking, arguing and working with other people. What Piaget, Vygotsky and Soviet psychologists discovered about the social roots of thinking, and how to use it at home and at school.
Attention, memory and strategies
Why does a child forget a long instruction halfway through, and why do some children solve problems better without being faster? What the information-processing approach has found about attention, memory and thinking strategies, and which study habits really work.
Differences and measurement
Why children are so different
Two children from one family can be strikingly unlike each other, and one child can be strong in one area and weak in another. What differential psychology says about individual differences and the bell curve, and why 'either/or' labels don't fit real children.
Heredity or upbringing? Both
Is a child's intelligence a gift of the genes or the result of upbringing? Twin and adoption studies, research on schooling and the Flynn effect show that the honest answer is 'both', and that heritable does not mean fixed. What this means for families.
What an IQ test can and cannot tell
An IQ score looks precise and final, yet it is a short sample of a child's behaviour compared with that of peers. How a test is built, what it predicts and what it misses, and what to ask when your child receives a result.
From theory to practice
Special abilities and choosing a path
Beyond general ability there are special ones: verbal, mathematical, spatial, mechanical, clerical and creative. How abilities, aptitudes and interests together point to a path, why guidance should help rather than dictate, and how a teenager can explore.
Ten everyday habits that help a child's mind grow
No expensive kits or courses are needed. Conversation, play, curiosity, manageable challenges, good sleep and warm relationships in which independence grows do the most for a child's thinking. Ten modest, research-based habits for any family.
A short history of the idea
Key steps in the study of intelligence, from the first tests to today's broader view of abilities.
- 1020
Ibn Sina (Avicenna)
Around 1020, in the Book of Healing (Kitab al-Shifa), Ibn Sina described the “inner senses” — common sense, imagination, memory and others — an early model of the mind's faculties. Read more
- 1838
Jean-Étienne Esquirol
Esquirol separated intellectual disability from mental illness and made a person's use of language the key criterion — one of the first steps towards assessing abilities. Read more
- 1869
Francis Galton
Galton published Hereditary Genius and made the first attempts to measure individual differences; he later brought correlation into psychology, a tool still used today. Read more
- 1879
Wilhelm Wundt
Wundt opened the first laboratory of experimental psychology in Leipzig, showing that mental processes could be studied and measured by experiment. Read more
- 1890
James McKeen Cattell
Cattell coined the term “mental test”; his tests of the senses and reaction speed predicted school success poorly, and researchers such as Binet turned to higher mental abilities. Read more
- 1904
Charles Spearman
Spearman noticed that people who do well on one mental test tend to do well on others and explained this with a general factor, g — still at the top of today's models of abilities. Read more
- 1905
Alfred Binet and Théodore Simon
Binet and Simon created the first practical intelligence scale to find pupils who needed extra help; Binet stressed that scores are provisional and that intelligence can be developed. Read more
- 1912
William Stern
Stern proposed the intelligence quotient (IQ): mental age divided by actual age, a single figure that made it easier to compare children of different ages. Read more
- 1916
Lewis Terman
At Stanford University Terman revised Binet's scale as the Stanford–Binet test and multiplied Stern's quotient by 100, creating the familiar IQ score. Read more
- 1934
Lev Vygotsky
Vygotsky's Thinking and Speech appeared in the year of his death, setting out the zone of proximal development: the gap between what a child can do alone and with help. Read more
- 1936
Jean Piaget
In The Origins of Intelligence in Children, based on watching his own three babies, Piaget argued that intelligence begins in action — looking, grasping, exploring — before words. Read more
- 1938
Louis Thurstone
Thurstone described about seven primary mental abilities, such as verbal comprehension, number and space, and urged looking at a profile of abilities rather than a single score. Read more
- 1939
David Wechsler
Wechsler published the Wechsler–Bellevue scale, with verbal and performance parts, and introduced the deviation IQ: a comparison with people of the same age that works for adults too. Read more
- 1947
Jean Piaget
In The Psychology of Intelligence, based on his lectures at the Collège de France, Piaget summed up his theory: intelligence is adaptation that grows more flexible and logical stage by stage. Read more
- 1950
J. P. Guilford
In his presidential address to the American Psychological Association, Guilford urged psychologists to study creativity, which had been largely neglected; research on it soon flourished. Read more
- 1956
George Miller
Miller's paper “The magical number seven, plus or minus two” showed how little we can hold in mind at once (about four chunks, by today's estimate) and why grouping information helps. Read more
- 1963
Raymond Cattell
Cattell distinguished fluid intelligence, used to solve new problems, from crystallised intelligence, the knowledge built up through learning — an idea he later developed with John Horn. Read more
- 1967
J. P. Guilford
In The Nature of Human Intelligence Guilford set out his structure-of-intellect model with 120 abilities; the model is now mostly history, but his divergent-thinking tasks are still used. Read more
- 1974
Marcel Detienne and Jean-Pierre Vernant
In The Ruses of Intelligence they reconstructed the Greek idea of mētis: shrewd, practical intelligence that reads changing situations and seizes the right moment. Read more
- 1983
Howard Gardner
In Frames of Mind Gardner proposed seven relatively independent intelligences, encouraging schools and parents to notice a wider range of strengths; the theory's scientific basis is still debated. Read more
- 1984
James Flynn
Flynn showed that average IQ test scores had risen from one generation to the next — about 3 points per decade — too fast for genes to explain, so the environment must matter a great deal. Read more
- 1985
Robert Sternberg
In Beyond IQ Sternberg proposed his triarchic theory — analytical, creative and practical abilities — and described intelligence as adapting to, shaping and choosing one's environment. Read more
- 1993
John Carroll
Re-analysing more than 460 data sets, Carroll proposed a three-stratum model — a general factor, broad abilities and narrow skills — the basis of today's mainstream CHC model. Read more
- 1999
Howard Gardner
In Intelligence Reframed Gardner added the naturalist intelligence — skill in recognising and classifying living things and other features of nature — bringing his list to eight. Read more
- 2008
Harold Pashler and colleagues
A major review found no sound evidence that matching teaching to pupils' supposed “learning styles” improves learning, so time is better spent on methods with proven benefits. Read more
- 2013
Jared Nielsen and colleagues
Brain scans of about 1,000 people revealed no “left-brained” or “right-brained” individuals: both hemispheres work together, so such labels say nothing about how a child learns. Read more