Influence of Laughter on Muscle Tone

Abstract

This study had its inception in the observation that in narcolepsy there occur attacks of cataplexy or tonelessness on emotion, especially during laughter and mirth. It was thought worth while to study by objective methods the effect of laughter on muscle tone.

The apparatus used was devised by Dr. L. C. Hutchinson of the University of Minnesota. The method consists essentially of passively flexing the forearm at a constant speed against a flat spring. The greater the resistance offered by the arm, the greater was the deflection of the spring. The spring was connected with a writing lever in such a way that the writing lever rose or fell with increasing or decreasing deflections of the spring. In this way the writer lever writing on a smoked drum described a tracing.

Experiments were done on 50 normal subjects. The first reading was taken with a calm facial expression. Then a reading was taken during laughter. Laughter was induced. In no instance was any considerable amount of mirth present but not all spontaneous laughter is due to mirth. It was thought possible that changes in muscle tone seen on laughter were due to the fact that the subject was distracted by his laughter, for this reason control readings were taken with the subject frowning to rule out the effect of distraction.

It was thought that the best method of measuring variations in muscle tone under the varying conditions of the experiment was to determine the differences in the amount of work done in passively moving the arm a certain distance. Since the area underneath a curve is an indicator of the amount of work done, the measurement of these areas and their comparison afforded a convenient method for the interpretation of the results.