Certain Physiological Changes Accompanying Prolonged Mental Reaction

Abstract

In an attempt to note the extent and to find the limits of certain suspected physiological changes produced during periods of prolonged mental effort, several series of carefully planned experiments were undertaken involving 3 subjects familiar with the solution of mental arithmetic problems. The task was uniform throughout and consisted in the solution of multiplication of 4 numbers by 4 numbers from memory alone. The level of metabolic rate was measured by oxygen consumption using the Graphic Metabolism machine. Changes in the blood elements, erythrocytes and leucocytes and changes in hemoglobin content were checked in the usual manner by use of the hemocytometer and the hemoglobinometer. Conspicuous changes in excretory products were determined by routine urine analyses, involving variations in specific gravity, reaction, occurrence of albumin and sugar, di-acetic acid and acetone. Five specific tests were made on each of the subjects, the first series to establish the “norms” without mental effort. The second series covered a one-hour concentration period. The succeeding tests were for 4, 8, and 12 hours duration, respectively, repeated on 4 successive days. Checks were made preceding and following the 4-day series to establish metabolic levels. In general there appears a slight rise in the metabolic level on the second day of the 12-hour series in 2 of the 3 subjects. On the third day the metabolic level of all 3 continued well above the basal rate, while records from the fourth day show an extremely high level in all subjects. The urine analysis showed fluctuations in specific gravity within normal limits; the reaction was from neutral to acid during the daily interval with no trace of either sugar or albumin in any subject.