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THE object of the present monograph is to furnish some accurate information on the much-discussed question of the psychology of the sexes. The main part of it consists in the report of a series of experiments carried on in the psychological laboratory of the University of Chicago during the years 1898-99 and 1899-1900. To have an adequate setting, such a study should be prefaced by a review of the historical aspects of the problem, a critical summary of the large mass of argumentative literature on the subject, and a discussion of the facts of anatomy and physiology which are supposed to have a bearing on the psychology of sex. The mass of material to be dealt with is far too great, however, to be satisfactorily treated within the necessary limits of the present work. It has therefore been necessary to restrict this monograph to a report of the experimental work which forms the real contribution to the field, a review of previous experimental work bearing on the subject, and a brief discussion of the results.

The present research is the first attempt to obtain a complete and systematic statement of the psychological likenesses and differences of the sexes by the experimental method. Needless to say, the goal has not been reached within the limits of such an investigation. All that has been done is to gather together some evidence bearing on the problem, which is trust-[p. 2]worthy so far as it goes. Previous experimental work has been in the form of detached experiments on some single sense or intellectual process. Usually the experiments have not been made for the purpose of a comparison of the sexes, but have been performed with some other interest in view, and have been incidentally formulated with reference to sex. Much of the material is the experimental work on school children done under the influence of the child-study movement. The only previous attempt to sum up the experimental evidence on the subject is that by Havelock Ellis (23), in his book Man and Woman, published in 1894. The work contains no original investigation.

In making a series of tests for comparative purposes, the first prerequisite is to obtain material that is really comparable. It has been shown that the simple sensory processes vary with age and with social condition (11, 20, 51, 54, 63, 64, 65, 67). No one would question that this statement is true for the intellectual processes also. In order to make a trustworthy investigation of the variations due to sex alone, therefore, it is essential to secure as material for experimentation, individuals of both sexes who are near the same age, who have the same social status, and who have been subjected to like training and social surroundings. The complete fulfilment of these conditions, even in the most democratic community, is impossible. The social atmosphere of the sexes is different from the earliest childhood to maturity. Probably the nearest approach among adults to the ideal requirement is afforded by the undergraduate stu-[p. 3]dents of a coeducational university. For most of them the obtaining of an education has been the one serious business of life. They have had at least the similarity of training and surroundings incident to school life. Most of those in a western university have received their preparatory education in coeducational schools

The individuals who furnished the basis for the present study were students of the University of Chicago. They were all juniors, seniors, or students in the first year of their graduate work. The original intention was to limit the ages to the period from twenty to twenty-five years. Owing to the difficulty of obtaining a sufficient number of subjects within these limits, a few individuals of nineteen years, and a few over twenty-five were admitted (see Fig. 81). The subjects were obtained by requesting members of the classes in introductory psychology and ethics to serve. They were told nothing about the object of the tests except that they were for the purpose of determining psychological norms. The series of questions on age, health, and nationality, reported in chap. viii, shows that in all these respects the men and women tested were closely comparable.

Two methods may be followed in planning a series of tests designed to yield material for the comparison of groups or classes. It is possible either to make rapid and more or less superficial measurements on a large number of individuals, depending on numbers to counterbalance the errors of single tests, or to make careful and accurate observations of a smaller number of persons. The ideal procedure would unquestionably be to make careful measurements of a large number of individuals, but since the amount of time [p. 4] available for any problem is limited, the practical question to be decided is -- Given a limited amount of time, which of the two modes of procedure mentioned is more likely to yield valuable results? Accuracy of measurement seemed an indispensable requirement for such a study as the present one. Any reliable determination of a threshold or a discriminative sensibility requires a somewhat extended series of experiments. With subjects untrained in psychological experiments -- as most of these were -- it is essential to take a large enough series of measurements to give some assurance that the results represent a characteristic reaction, and not haphazard answers. In so simple a test as that of dermal two-point discriminations the first few judgments are very likely to be little more than guesses. In a series of rapid tests like those employed at Columbia University (82) the subject is given only five stimulations with the æsthesiometer. The points are kept a fixed distance apart and the subject is given both one- and two-point stimulations in his series of five. It seems improbable that the results of such a test on unpracticed subjects mean anything more than random answers. The Columbia experiments on a large number of students failed to reveal any difference of sex in the fineness of two-point discriminations, while the present accurate measurement of fifty subjects shows a clear difference.

The series of tests employed in this investigation required from fifteen to twenty hours of time from each subject. The hours were arranged from one sitting to the next according to the convenience of the subject. It was not possible to have the hours for any one test constant for all subjects, since the [p. 5] schedules varied so widely. No attempt was made to keep the order of experiments rigidly the same for all. Convenience and economy of time necessarily determined the order to a great extent. In general, however, the simple sensory and motor tests were given in the early part of the series, and the intellectual tests in the latter part. The questions on personality usually came last. The taste and smell experiments had to be scattered through most of the periods, since only a few at a time could be performed without fatigue. The entire series was applied to fifty subjects, twenty-five men and twenty-five women.

The experiments fell into seven groups, dealing respectively with motor ability, skin and muscle senses, taste and smell, hearing, vision, intellectual faculties, and affective processes. One chapter of this monograph is devoted to each group. A list of the experiments under each group will be found at the beginning of each chapter. At the end of each chapter there is a comparison of results with those of other investigators, and a general summary. The numbers in parentheses used in the summaries of other experimental work and throughout the text, refer to the bibliography at the end of the volume. The bibliography pretends to completeness only in its enumeration of the experimental researches bearing on the problem, and even here there are doubtless omissions, although it is hoped that all the important papers are mentioned. Whenever for the sake of brevity a dogmatic statement is made to the effect that there are no data on a certain point, or only such data as are quoted, the qualification, so far as the author knows, is to be understood.[p. 6]

The report of each experiment includes a description of the apparatus used, a statement of the method, and a formulation of the results. Since the value of experimental work, and the possibility of comparing one set of results with another depend so largely upon the method, the greatest pains has been taken to secure uniformity, and to describe the method in full in each case. The experiments were all performed by the author, with the exception of a part of the reaction-time tests, which had to be repeated because of a source of error in the apparatus. For these the author is indebted to Dr. W. C. Gore and Mr. H. J. Pearce, of the Graduate School of the University of Chicago.

A few words in general on the methods employed may not be out of place, in spite of the fact that each is described in full in connection with the test. The guiding principle in selecting the method was the desire to make the directions to the subject as clear and simple as possible and at the same time secure the greatest possible accuracy of result. In all the tests on discriminative sensibility this double end seemed best secured by requiring a simple judgment of comparison (i. e., lighter or heavier, more or less cold, etc.) between two stimuli. The subject was told nothing of a standard stimulus, and the order of the standard and stimulus of comparison was varied. The difference in intensity between the standard and the stimulus of comparison was varied until the point was found at which three-fourths of the judgments were correct. In the threshold tests of taste and smell, tasteless and odorless preparations were used to control the threshold illusions. The greatest care was taken to avoid [p. 7] suggestion of all sorts in all the tests. The descriptions of method have been made explicit at the risk of their being perhaps somewhat tedious and needlessly detailed.

The results of the experiments have been presented graphically wherever possible. In all the curves, the dotted line is for women and the unbroken line for men. The ordinates always represent the number of subjects. In no case have the results been averaged. Wherever graphic representation was impracticable, they have been grouped. The purpose of the research was norms, not averages.