The measurements of the neuro-muscular processes and the general mental condition of the men in Squads A and B were made at the Nutrition Laboratory when the men were in Boston, Saturday evenings and Sunday mornings. This arrangement of bringing the squads to Boston was a particularly advantageous one for the psychological phase of this research, as it made possible the securing of a maximum amount of data in the time at our disposal, with the least interference with the college duties of the subjects. Moreover, by doing this part of the work at the Nutrition Laboratory conditions were obtained which were more suitable and uniform throughout the experimentation than they would probably have been elsewhere. The students were away from their usual college environment, with its numerous interests and distractions. The college work for the week was completed. Since the men were all present and had no other duties or engagements than to serve as subjects in the psychological and other measurements, it was unnecessary to make individual appointments for an experimental session, a condition which unavoidably gives rise to many irregularities. All of the men in one squad could thus be measured on one day within a period of 4 hours and following the ingestion of a standard meal which was uniform for each time they were present. (See p. 262.) Physical activity during the hours preceding the evening session was also made uniform by the necessity of the railroad journey from Springfield to Boston.

1 Benedict and Talbot, Carnegie Inst. Wash. Pub. No. 201, 1914, p. 29.

At the Nutrition Laboratory certain apparatus and techniques were available which, under the circumstances, could not well have been transferred to Springfield. Early in September, as has been explained previously (see p. 44), there was considerable doubt as to the possibilities in the experiment. The enrollment at the college was small and many of the older students would probably be called for Government service. It was of course impossible to know whether the students would volunteer as subjects, and, if so, how many would be available for the experiment. Furthermore, as in the preliminary plans it was thought desirable to continue the experiment only to the Christmas vacation, it was necessary that when college did open, the experiment, if it was to be started, should begin immediately. By coming to the Nutrition Laboratory for the psychological measurements the greater part of the apparatus would be in readiness and thus a minimum of experimental opportunity would be lost. Some of the apparatus and technique had been previously elaborated in connection with other problems with the object of securing measurements and procedures which could be repeated on the same individual without the development of large practice changes. Great care had been taken to make the measurements as objective and free from personal bias as possible. Many of them will be noted to have a distinct physiological trend. The avoidance of all practice changes with fluctuations in interest and attention is of course an ideal which is never quite reached in psychological investigations, but it is believed that the measurements, procedures, and conditions in the present research all contributed to minimizing the influence of these factors. The interval of two weeks which came between experimental sessions of the same squad was also useful for this purpose.

In planning this phase of the investigation there were several considerations which favored the use of a wide range of neuro-muscular measurements. The nature and extent of the effects of prolonged reduced diet could not be anticipated, and for this reason these effects should be given as many opportunities as practicable to show themselves. Our men were not what might be termed trained psychological subjects; they had received but slight practice in introspection. The tests were given in the evening. Under these conditions prolonged measurement* of one kind would have favored development of sleepiness and fatigue. The physical movements and frequent changes necessitated by the large variety of measurements prevented ennui.

A serious effort was made to secure sufficient data for every measurement with each subject to obtain a fair sample of the subject's performance. Usually not more than 10 to 12 minutes was required for any one measurement, while certain of the measurements required a period of only 5 minutes or even less. Under normal circumstances this is not sufficient to cause ennui or fatigue.

The large variety of measurements made possible the employment of several men at the same time. Not infrequently a man may have some physical limitation which makes one or more of the measurements difficult or unpleasant to him. For example, he may have poor eyes, the knee-jerk may be absent, or he may believe that his memory is very poor. Such circumstances favor short intensive tests and several of them.

Psychological Measurements Used

The measurements which were chosen for this investigation may be catalogued under two heads:

First, those given to the men as a group, that is, when all the men served as subjects at the same time, at the beginning of each evening session. These, listed more or less in their order of complexity, were:

(1) Accuracy in tracing between irregular parallel lines.

(2) Discrimination for the pitch of tones.

(3) Discrimination for specified number groups on a printed page.

(4) Addition of one-place numbers for a period of 10 minutes.

(5) Memory span for 4-letter English words.

Second, measurements given to the men individually; that is, when one man was tested at a time. These, numbered serially from the measurements previously given and listed in approximate order of increasing complexity, were:

(6) Strength of grip (evening and morning).

(7) Changes in pulse rate occasioned by short periods of exertion (morning).

(8) Latency, amplitude, and refractory period of the patellar reflex.

(9) Reaction time for turning the eye to a new point of regard (morning).

(10) Reaction time for speaking 4-letter words.

(11) Continuous discrimination and reaction in finding serial numbers.

(12) Sensory threshold for visual efficiency (acuity).

(13) Sensory threshold for electric shock.

(14) Speed of the eye movements (morning).

(15) Speed of the finger movements (evening and morning).

(16) Efficiency in traversing a right-angle maze.

(17) Efficiency in performing certain clerical tasks.