In courses where the aim is to teach socially necessary information or to give a comprehensive view of the scope of a specific subject, it is obvious that the laboratory method will lead far afield. It is for this reason that introductory courses given in recitations, with demonstrations by instructors, and occasional lecture and laboratory hours, are more liberalizing in their influence upon the beginners than courses that are primarily laboratory in character.
=Cautions in the use of the laboratory method=
Most laboratory courses would enhance their usefulness by observing a few primary pedagogical maxims. The first of these counsels that we establish most clearly the distinctive aim of the course. The instructor must be sure that he has no quantitative aim to attain but is occupied rather with the problems of teaching the method of his specialty. Second, an earnest effort must be made to acquaint the students with the general aim of the entire course as well as with the specific aim of each laboratory exercise. The students must be made to realize that they are not discovering new principles but that by rediscovering old knowledge or testing the validity of well-established truths they are developing not only the technique of investigational work, but also a set of useful mental habits. Much in laboratory work seems needless to the student who does not perceive the goal which every task strives to attain.
A third requisite for successful laboratory work requires so careful a gradation that every type of problem peculiar to a subject is made to arise in the succession of exercises. It is wise at times to set a trap for students so that they may learn through the consequences of error. For this reason students may be permitted to leap to a conclusion, to generalize from insufficient data, to neglect controls, to overlook disturbing factors, etc. An improperly planned and poorly graded laboratory course repeats exercises that involve the same problems and omits situations that give training in attacking and solving new problems.
Effective laboratory courses afford opportunity to students to repeat those exercises in which they failed badly. If each exercise in the course is designed to make a specific contribution to the development of the student, it is obvious that merely marking the student zero for a badly executed experiment is not meeting the situation. He must in addition be given the opportunity to repeat the experiment in order to derive the necessary variety of experiences from his laboratory training. And, finally, the character of the test that concludes a laboratory course must be considered. The test must be governed by the same underlying aims that determine the entire course. It must seek to reveal, not the mastery of facts, but growth in power. It must measure what the student can do rather than what he knows. A properly organized test serves to reinforce in the minds of students the aims of the entire course.