Rogers and McIntyre. Brit. J. of Psychol., 1914, 7: 265-299.
Each of the studies indicated in the table, except that of Bloch and Preiss, gives evidence that the XII-year tests are too difficult for 12-year-old children. Moreover, we find that in the 1911 revision of their scale Binet and Simon advanced their 1908 XII-year tests to test-age XV and four out of the five XI-year tests to test-age XII. Passing the XII-year (1908) tests would, therefore, seem to bring a child above the upper limit of feeble-mindedness as defined even by the American Association for the Study of Feeble-mindedness, since it means more than the intelligence of a child of 12.
Goddard still adhered to this borderline of the American Association in 1914 in his work on Feeble-Mindedness. He says: “We have practically agreed to call all persons feeble-minded who do not arrive at an intelligence higher than that of the twelve year old normal child” (p. 573). In the same year Schwegler's “Teachers' Manual” for the use of the Binet scale says that a person who tests XII is a moron if mature ([180]). Since the evidence of Table IV indicates that 75% of the twelve-year-olds do not test above XI, even those who adhere to the high limit of the intelligence of a 12-year-old should have required an adult to test XI on the Binet scale in order to show deficiency.
In 1911 we find Wallin writing, regarding the 1908 tests, “it is a question whether the line of feeble-mindedness should not be drawn between eleven and twelve instead of between twelve and thirteen.... A number of our twelve-year-olds are certainly very slightly, if at all, feeble-minded” ([210]). Jennings and Hallock ([31]) and Morrow and Bridgman ([39]) in testing delinquents reported in 1911 and 1912 that they regarded those passing the tests for twelve years as socially fit. Chotzen ([31]) thinks that the two children in his group of pupils from a Hilfsschule who test ten and are three years or more retarded are not feeble-minded. Davis thinks that those “showing mentality from ten to twelve years” may possibly not be called mentally defective (133, p. 187).
In 1915 the editors of the magazine “Ungraded” in their recommendations regarding the use of the Binet scale say “a mental age of 10 or above is not necessarily indicative of feeble-mindedness, regardless of how old the examinee may be” (66, p. 7). In the same year Kohs, in reporting the examinations of 335 consecutive cases at the Chicago House of Correction, says: “We find normality to range within the limits 122 and 104 and feeble-mindedness not to extend above the limit 112. In other words, none of our cases testing 113 or over was found, with the aid of other confirmatory data, to be mentally defective. None of our cases testing 103 or below was found to be normal. Of those testing between 104 and 112, our borderline cases, a little less than half were found normal, and somewhat more than half were found feeble-minded” ([33]). His exponents here refer to number of tests and not to tenths of a test-year. Hinckley ([182]) reports examinations with the Binet 1911 scale on 200 consecutive cases at the New York Clearing House for Mental Defectives which show that with these suspected cases, which were from 13 to 43 years of age, seven-eighths tested X or below. Referring to adults, Wallin states that he has “provisionally placed the limen somewhere between the ages of IX and X” ([215]). Dr. Mabel Fernald at the Bedford Reformatory laboratory said in 1917, “many of us for some time have been using a standard that only those who rank below ten years mentally can be called feeble-minded with certainty” ([16]). The reader should also see the admirable review and discussion of the borderlines on the Binet scale in Chap. II of Wallin's Problems of Subnormality. Two descriptions of the scale borderlines in books on mental testing which appeared in 1917 are of interest. In his Clinical Studies in Feeble-Mindedness (p. 76), E. A. Doll says:
“By the Binet-Simon method feeble-mindedness is almost always (probably more than 95 times in a hundred) an accurately safe diagnosis when the person examined exhibits a mental age under 12 years with an absolute retardation of more than three years, or a relative retardation of more than 25 per cent.”
N. J. Melville, in his Standard Method of Testing Juvenile Mentality (p. 10), says:
“Conservative estimates today place the upper limit of feeble-mindedness at least in a legal sense at Binet age ten; others place it at Binet age eleven.... A Binet age score below eleven when accompanied by a sub-age (retardation) of more than three years is usually indicative of serious mental deficiency. Even when accompanied by a slight sub-age score, a Binet age score below eleven may be indicative of potential mental deficiency when the test record reveals a Binet base that is six or more years below the life age.”
In 1916 the new Stanford scale appeared and its tests are arranged so that approximately 50% of each age instead of 75%, test at age or above. Even with this lowering of the scale units, Dr. Terman describes his borderline for “definite feeble-mindedness” as below an intelligence quotient of 70. This would mean for his 16-year-old mature borderline a mental age on this scale of XI.2. We have no means of determining to what positions these points on the Stanford scale would correspond on the 1908 or 1911 Binet scales. Dr. Terman says “the adult moron would range from about 7-year to 11-year intelligence” ([57]). Apparently also referring to the Stanford scale, the physicians at the Pediatric Clinic of that university agree with this borderline and say: “morons are such high grade feeble-minded as never at any age acquire a mental age greater than 10 years” ([169]). That there is still need for more caution is evidenced by the statement of a prominent clinician in 1916 that “cases prove ultimately to be feeble-minded since they never develop beyond 12 years intelligence” ([135]).
Most interesting perhaps is the fact that Binet and Simon themselves, the collaborators who first formulated the scale for measuring intelligence by mental ages, after their years of experience with the tests came, by rule of thumb, to regard IX as the highest level reached by those testing deficient. Dr. Simon stated the borderline for the mature in this way in a paper read in England in 1914 and published the next year. He said: