To break this circle, it indeed becomes necessary to emancipate one's self from the method of ordinary self-observation and to replace it by objective experiment in the psychological laboratory. Experimentation in such a laboratory stands in no contrast to the method of introspection. A contrast does exist between self-observation and observation on children or patients or primitive peoples or animals. In their case the psychologist observes his material from without. But in the case of the typical laboratory experiment, everything is ultimately based on self-observation; only we have to do with the self-observation under exact conditions which the experimenter is able to control and to vary at will. Even Parsons sometimes turned to little experimental inquiries in which he simplified some well-known methods of the laboratory in order to secure with the most elementary means a certain objective foundation for his mental analysis. For instance, he sometimes examined the memory by reading to the boys graded sentences containing from ten to fifty words and having them repeat what they remembered, or he measured with a watch the rapidity of reading and writing, or he determined the sensitiveness for the discrimination of differences by asking them to make a point with a pencil in the centres of circles of various sizes. But if such experimental schemes, even of the simplest form, are in question, it seems a matter of course that the plan ought to be prescribed by real scientists who specialize in the psychological field. The psychologist, for instance, surely cannot agree to a method which measures the memory by such a method of having spoken sentences repeated and the quality of the memory faculty naïvely graded according to the results. He knows too well that there are many different kinds of memory, and would always determine first which type of memory functions is to be examined if memory achievements are needed for a particular calling.