The Measurement of Intelligence. Lewis M. Terman
Essential nature of the scale.
The Binet scale is made up of an extended series of tests in the nature of “stunts,” or problems, success in which demands the exercise of intelligence. As left by Binet, the scale consists of 54 tests, so graded in difficulty that the easiest lie well within the range of normal 3-year-old children, while the hardest tax the intelligence of the average adult. The problems are designed primarily to test native intelligence, not school knowledge or home training. They try to answer the question “How intelligent is this child?” How much the child has learned is of significance only in so far as it throws light on his ability to learn more.
Binet fully appreciated the fact that intelligence is not homogeneous, that it has many aspects, and that no one kind of test will display it adequately. He therefore assembled for his intelligence scale tests of many different types, some of them designed to display differences of memory, others differences in power to reason, ability to compare, power of comprehension, time orientation, facility in the use of number concepts, power to combine ideas into a meaningful whole, the maturity of apperception, wealth of ideas, knowledge of common objects, etc.
How the scale was derived.
The tests were arranged in order of difficulty, as found by trying them upon some 200 normal children of different ages from 3 to 15 years. It was found, for illustration, that a certain test was passed by only a very small proportion of the younger children, say the 5-year-olds, and that the number passing this test increased rapidly in the succeeding years until by the age of 7 or 8 years, let us say, practically all the children were successful. If, in our supposed case, the test was passed by about two thirds to three fourths of the normal children aged 7 years, it was considered by Binet a test of 7-year intelligence. In like manner, a test passed by 65 to 75 per cent of the normal 9-year-olds was considered a test of 9-year intelligence, and so on. By trying out many different tests in this way it was possible to secure five tests to represent each age from 3 to 10 years (excepting age 4, which has only four tests), five for age 12, five for 15, and five for adults, making 54 tests in all.
List of tests.
The following is the list of tests as arranged by Binet in 1911, shortly before his untimely death:—
1 Age 3:Points to nose, eyes, and mouth.Repeats two digits.Enumerates objects in a picture.Gives family name.Repeats a sentence of six syllables.
2 Age 4:Gives his sex.Names key, knife, and penny.Repeats three digits.Compares two lines.
3 Age 5:Compares two weights.Copies a square.Repeats a sentence of ten syllables.Counts four pennies.Unites the halves of a divided rectangle.
4 Age 6:Distinguishes between morning and afternoon.Defines familiar words in terms of use.Copies a diamond.Counts thirteen pennies.Distinguishes pictures of ugly and pretty faces.
5 Age 7:Shows right hand and left ear.Describes a picture.Executes three commissions, given simultaneously.Counts the value of six sous, three of which are double.Names four cardinal colors.
6 Age 8:Compares two objects from memory.Counts from 20 to 0.Notes omissions from pictures.Gives day and date.Repeats five digits.
7 Age 9:Gives change from twenty sous.Defines familiar words in terms superior to use.Recognizes all the pieces of money.Names the months of the year, in order.Answers easy “comprehension questions.”
8 Age 10:Arranges five blocks in order of weight.Copies drawings from memory.Criticizes absurd statements.Answers difficult “comprehension questions.”Uses three given words in not more than two sentences.
9 Age 12:Resists suggestion.Composes one sentence containing three given words.Names sixty words in three minutes.Defines certain abstract words.Discovers the sense of a disarranged sentence.
10 Age 15:Repeats seven digits.Finds three rhymes for a given word.Repeats a sentence of twenty-six syllables.Interprets pictures.Interprets given facts.
11 Adult:Solves the paper-cutting test.Rearranges a triangle in imagination.Gives differences between pairs of abstract terms.Gives three differences between a president and a king.Gives the main thought of a selection which he has heard read.
It should be emphasized that merely to name the tests in this way gives little idea of their nature and meaning, and tells nothing about Binet’s method of conducting the 54 experiments. In order to use the tests intelligently it is necessary to acquaint one’s self thoroughly with the purpose of each test, its correct procedure, and the psychological interpretation of different types of response.[10]
In fairness to Binet, it should also be borne in mind that the scale of tests was only a rough approximation to the ideal which the author had set himself to realize. Had his life been spared a few years longer, he would doubtless have carried the method much nearer perfection.
How the scale is used.
By means of the Binet tests we can judge the intelligence of a given individual by comparison with standards of intellectual performance for normal children of different ages. In order to make the comparison it is only necessary to begin the examination of the subject at a point in the scale where all the tests are passed successfully, and to continue up the scale until no more successes are possible. Then we compare our subject’s performances with the standard for normal children of the same age, and note the amount of acceleration or retardation.
Let us suppose the subject being tested is 9 years of age. If he goes as far in the tests as normal 9-year-old children ordinarily go, we can say that the child has a “mental age” of 9 years, which in this case is normal (our child being 9 years of age). If he goes only as far as normal 8-year-old children ordinarily go, we say that his “mental age” is 8 years. In like manner, a mentally defective child of 9 years may have a “mental age” of only 4 years, or a young genius of 9 years may have a mental age of 12 or 13 years.
Special characteristics of the Binet-Simon method.
Psychologists had experimented with intelligence tests for at least twenty years before the Binet scale made its appearance. The question naturally suggests itself why Binet should have been successful in a field where previous efforts had been for the most part futile. The answer to this question is found in three essential differences between Binet’s method and those formerly employed.
1. The use of age standards.
Binet was the first to utilize the idea of age standards, or norms, in the measurement of intelligence. It will be understood, of course, that Binet did not set out to invent tests of 10-year intelligence, 6-year intelligence, etc. Instead, as already explained, he began with a series of tests ranging from very easy to very difficult, and by trying these tests on children of different ages and noting the percentages