As rapidly as reliable norms are established, it becomes possible to select for each age, school grade, occupation, etc., a set of tests which the average person of that age, schooling or calling should be able to perform to a certain known degree of proficiency. Failure to accomplish this indicates performance lower than that expected and in so far as success is dependent solely on mental ability, indicates inferior capacity. Similarly, ability to do more than the average or normal record requires indicates a capacity that is precocious, rare, and superior. In this way are derived standard graded scales which represent a decided advance in the science of psychological diagnosis. There are three rather different forms in which attempts have been made to secure such scales. In one form the scale consists of a series of steps, each step consisting of different sorts of performance; that is, different tests or tasks are used. These tasks are arranged in groups, each group representing tests which should be passed acceptably by individuals of the given age, school grade, etc. In another form of scale the type of task is the same throughout, but the different points on the scale are represented by increasingly difficult specimens of material. The scale thus presents graded steps of difficulty in doing the same general sort of thing. In the third form the task remains precisely the same throughout, and performance is measured in terms of the time in which the task can be completed and the accuracy which is displayed. Sometimes, in scales of this type, although the instructions are always the same, the test is performed with varying degrees of approximation to a qualitative standard, and the steps may then consist of these graded qualitative achievements. As representative of the first form of scale we may refer to the widely used Binet-Simon scale for the determination of mental age. Whatever we mean by intelligence, it is a characteristic which is essential to vocational activity. It is furthermore a characteristic which normally tends to increase in its degree or manifestation from infancy up to at least ten or twelve years of age. Beyond that point there are, to be sure, striking individual differences in that characteristic which we call intelligence, but beyond this point it does not seem so dependent on the physical age of the organism. Five-year-old children tend to be pretty much alike in intelligence. At least, the change from five years to seven years is commonly attended by very apparent growth in this respect, and a five-year-old is more like other five-year-olds in the things he can do than he is like seven-year-olds.