Consequences of Laughter Upon Trunk Compression and Cortical Activation: Linear and Polynomial Relations

Abstract

Results from two studies of biological consequences of laughter are reported. A proposed inhibitory brain mechanism was tested in Study 1. It aims to protect against trunk compression that can cause health hazards during vigorous laughter. Compression may be maximal during moderate durations and, for protective reasons, moderate in enduring vigorous laughs. Twenty-five university students volunteered to see a candid camera film. Laughter responses (LR) and the superimposed ha-responses were operationally assessed by mercury-filled strain gauges strapped around the trunk. On average, the thorax compression amplitudes exceeded those of the abdomen, and greater amplitudes were seen in the males than in the females after correction for resting trunk circumference. Regression analyses supported polynomial relations because medium LR durations were associated with particularly high thorax amplitudes. In Study 2, power changes were computed in the beta and alpha EEG frequency bands of the parietal cortex from before to after exposure to the comedy "Dinner for one" in 56 university students. Highly significant linear relations were calculated between the number of laughs and post-exposure cortical activation (increase of beta, decrease of alpha) due to high activation after frequent laughter. The results from Study 1 supported the hypothesis of a protective brain mechanism that is activated during long LRs to reduce the risk of harm to vital organs in the trunk cavity. The results in Study 2 supported a linear cortical activation and, thus, provided evidence for a biological correlate to the subjective experience of mental refreshment after laughter.

Keywords: cortical activation; laughter; linear; polynomial; trunk compression.

Figure 1

Illustration of trunk circumference changes (compressions) during laughter induced by a video entertainment program (“Dinner for one”). Changes are traced by a mercury-filled strain gauge strapped around the abdomen, and regular breathing amplitudes are indicated to the far left in the figure. Arrows indicate the occurrence of laughter.

Figure 2

Linear and polynomial relations between (a) total number of laughter responses (LRs) and (b) mean duration of the five longest LRs.

Figure 3

Linear and polynomial relations between (a) the total number of laughter responses and (b) abdominal and thoracic compression amplitudes during laughter (upper panels) as well as frequencies of abdominal and thoracic HA-responses (lower panels).

Figure 4

Linear and polynomial relations between (a) the mean duration of the five longest laughter responses and (b) abdominal and thoracic compression amplitudes during laughter (upper panels) as well as frequencies of abdominal and thoracic HA-responses (lower panels).

Figure 5

Changes in parietal cortex EEG power (pre-to-post comedy change scores) as consequences of laughter during exposure to a comedy (“Dinner for one”). Left panel: Beta band (EEG-B). Right panel: Alpha band (EEG-A). The 95% confidence intervals are given as dotted lines around the regression lines.