At the outset of this experiment it was very difficult to decide which, out of the innumerable activities suggested for a psychologist in schools, should be selected. At first this difficulty seemed to be only an added technical complication of the work, but gradually it became clear that instead of something superimposed it really represented the core of the problem to be studied; superficially it had looked as if the Head Mistresses had asked for a psychologist to come and contribute, by means of experiment, certain clearly defined items of technical information to help them in solving their day to day problems. But it soon appeared that the introduction of a new kind of expert into any social organization is an experiment in itself, and that the exact position of the psychologist within the school was not something that could be taken for granted. Thus the aim of the experiment gradually became, as far as the experimenter was concerned, not so much to be as useful as possible, but to try to define in what ways a psychologist could be useful.