The following tests are the ones most subject to the influence of coaching: Ball and field, giving date, naming sixty words, finding rhymes, changing hands of clock, comprehension of physical relations, “induction test,” and “ingenuity test.”
In several instances we have interviewed children an hour or two after they had taken the examination, in order to find out how many of the tests they could recall. A boy of 4 years, after repeated questioning, could only say: “He showed me some pictures. He had a knife and a penny. He told me to shut the door.” A girl of 3 years could recall nothing whatever that was intelligible.
An 8-year-old boy said: “He made me tie a knot. He asked me about a ship and an auto. He wanted me to count backwards. He made me say over some things, numbers and things.”
A boy of 12 years said: “He told me to say all the words I could think of. He said some foolish things and asked what was foolish [he could not repeat a single absurdity]. I had to put some blocks together. I had to do some problems in arithmetic [he could not repeat a single problem]. He read some fables to me. [Asked about the fables he was able to recall only part of one, that of the fox and the crow.] He showed me the picture of a field and wanted to know how to find a ball.”
It is evident from the above samples of report that the danger of coaching increases considerably with the age of the children concerned. With young subjects the danger is hardly present at all; with children of the upper-grammar grades, in the high school, and most of all in prisons and reformatories, it must be taken into account. Alternative tests may sometimes be used to advantage when there is evidence of coaching on any of the regular tests. It would be desirable to have two or three additional scales which could be used interchangeably with the Binet-Simon.
Reliability of repeated tests.
Will the same tests give consistent results when used repeatedly with the same subject? In general we may say that they do. Something depends, however, on the age and intelligence of the subject and on the time interval between the examinations.
Goddard proves that feeble-minded individuals whose intelligence has reached its full development continue to test at exactly the same mental age by the Binet scale, year after year. In their case, familiarity with the tests does not in the least improve the responses. At each retesting the responses given at previous examinations are repeated with only the most trivial variations. Of 352 feeble-minded children tested at Vineland, three years in succession, 109 gave absolutely no variation, 232 showed a variation of not more than two fifths of a year, while 22 gained as much as one year in the three tests. The latter, presumably, were younger children whose intelligence was still developing.
Goddard has also tested 464 public-school children for three successive years. Approximately half of these showed normal progress or more in mental age, while most of the remainder showed somewhat less than normal progress.
Bobertag’s retesting of 83 normal children after an interval of a year gave results entirely in harmony with those of Goddard. The reapplication of the tests showed absolutely no influence of familiarity, the correlation of the two tests being almost perfect (.95). Those who tested “at age” in the first test had advanced, on the average, exactly one year. Those who tested plus in the first test advanced in the twelve months about a year and a quarter, as we should expect those to do whose mental development is accelerated. Correspondingly, those who tested minus at the first test advanced only about three fourths of a year in mental age during the interval.[39]