As I’m sure you have figured out by now, I enjoy finding proof that we humans, Homo sapiens sapiens, are not that different from other forms of life. We share many characteristics with the other living creatures with whom we share our planet. Today, I have one more example for you—laughter.
Laughing is an involuntary reaction in humans consisting of rhythmical contractions of the diaphragm and other parts of the respiratory system. It is elicited mostly by external stimuli like being tickled. We associate it primarily with joy, happiness, and relief, but fear, nervousness and embarrassment may also cause it. Laughter depends on early learning and cultural factors.
The study of humor and laughter is called gelotology from the Greek gelos (γέλιο) meaning laughter.
Chimpanzees, gorillas, bonobos, and orangutans display laughter-like behavior when wrestling, play chasing, or tickling. It is difficult for us to recognize their laughter because it is generated by alternating inhalations and exhalations that sound to us like breathing and panting.
Rats display long, high frequency, ultrasonic vocalizations during play and when tickled. We can only hear these chirping sounds with special equipment. They are also ticklish, as we are, and certain areas of their body are more sensitive than others. The rat laughter is associated with pleasant feelings. Social bonding occurs with the human tickler, and the rats can even become conditioned to seek the tickling.*
A dog’s laughter sounds similar to a normal pant. Performing a sonograph analysis of this panting behavior shows that the variation of the bursts of frequencies is similar to the laughing sound. When we play this recorded dog-laughter to dogs in a shelter, it can contribute to promoting play, social behavior, and decrease stress levels.*
Victor Borge once said, “Laughter is the shortest distance between two people.” Maybe it is simply the shortest distance between any two living creatures. Keep laughing, my friends!
* Panksepp & Burgdorf, 2003, ‘Laughing’ rats and the evolutionary antecedents of human joy?; Simonet, Versteeg & Storie, 2005, Dog-laughter: Recorded playback reduces stress related behavior in shelter dogs.
If animal behavior fascinates you, you will enjoy "Ethology—The Study of Animal Behavior in the Natural Environment," the book and course by ethologist Roger Abrantes.