Alfred Binet, answered from the texts and cited to the page.
The scale Simon and I built is, at its foundation, a practical instrument for a practical problem: to identify, among the children of Paris, those who could not profit from ordinary instruction and needed something different. That purpose shaped every decision we made in constructing it. What we produced is a graded series of tasks, arranged in order of increasing difficulty, calibrated against what children of each age can actually do.
A child of seven is asked to do what seven-year-olds ordinarily manage; if he cannot, we know something precise — not merely that he is "dull," which tells us nothing, but that he performs at the level of a five-year-old, which tells us a great deal. The retardation is expressed as the gap between his mental level and his chronological age.1
The tasks themselves are not sensory measurements — not the keenness of an eye or the speed of a reflex — but the mind's own proper work: to repeat a sentence, to define a word, to compare two objects, to execute a commission, to find what is absurd in a picture.2 These are the operations that constitute intelligence, and only by engaging them can one measure them.
The order of difficulty in the scale is not a conjecture; it is the result of many trials on actual children.3 We discovered, for instance, that the ability to repeat five figures rather than three requires the full span of years between four and seven — a finding no armchair theorist would have predicted. The scale proved itself by predicting what we wished to predict: the child's capacity to learn and to follow instruction.
What the scale yields is a present state, a performance here and now. It is a diagnosis, not a sentence. We possess an instrument that allows us to measure the intellectual development of young children between three and twelve years of age, and the examination need not take more than thirty minutes.4 That result tells us which children need our help; it does not tell us that our help is useless.
To recapitulate, he has, with indulgence, the mental level of five years... He is two years behind his age, that is —2.The Development of Intelligence in Children
Definitions. — He gave them by use only, as at six years. Q. A fork? A. Silence. Q. A table. A. It is for eating.The Development of Intelligence in Children
It is as the result of many trials, that we have established this order; we have by no means imagined that which we present.The Development of Intelligence in Children
Our principal conclusion is that we actually possess an instrument which allows us to measure the intellectual development of young children whose age is included between three and twelve years... the performance of these tests certainly does not require more than thirty minutes.The Development of Intelligence in Children