In many of the experiments discussed it can be observed that the control groups, as well as the experimental groups, often show considerable gains. This is, in large part, due to the practice effect of experience with the test. Since, in many of these cases, few if any of the students had previously taken an intelligence test, the effect of practice may have been especially marked. The duration of the coaching effect was of interest to many of these investigators; the effect of coaching has been shown not to be permanent. It should be pointed out that the evidence is not clear as to whether coaching on similar materials for the Stanford-Binet has a significant effect, but coaching on materials identical to those in this test does produce very highly significant differences. Specific training in reading and in semantics was also found to result in gains on intelligence tests.