For many years psychologists and behavioral biologists agreed that laughter was a unique emotional expression found only in humans. However, as the study of animal emotions expanded this idea was called into question. The Nobel Prize winning ethnologist, Konrad Lorenz suggested that dogs are capable of laughing. He says that it is during play that dogs actually appear to laugh. In his book Man Meets Dog, Lorenz describes it this way:
"...an invitation to play always follows; here the slightly opened jaws which reveal the tongue, and the tilted angle of the mouth which stretches almost from ear to ear give a still stronger impression of laughing. This ‘laughing' is most often seen in dogs playing with an adored master and which become so excited that they soon start panting".
It is this panting which Lorenz identified with human laughter. Although he may have been one of the first to suggest that dogs laugh, the idea that other animals laugh had already been suggested by earlier scientists. Charles Darwin started the ball rolling in his book The Expression of Emotions in Man and Animals published in 1872. He noticed that chimpanzees and other great apes produce a laugh-like sounds when they are tickled or when they are playing. More recently Jane Goodall described this same ‘‘laughing'' and ‘‘chuckling'' reported by Darwin and others as a sort of breathy panting that can escalate to a more guttural ‘‘ah-grunting,'' if intense. The general consensus is that this ape laughter sounds somewhat like the heavy breathing that might simply result from vigorous play is meant to be a signal of their playful intentions. According to Robert Provine, a psychologist at the University of Maryland Baltimore County, the sound of chimpanzee laughter is much breathier that that of humans which tends to chop the laugh sounds into short "ha-ha" sounds. Instead there are longer pant sounds with each inward and outward breath.
Research done by Patricia Simonet at Sierra Nevada College in Lake Tahoe looked at laughter sounds in dogs. Simonet's team investigated the question by standing in parks with a parabolic microphone that allowed them to record the sounds that dogs made while playing from a distance. In describing the laughter sounds of dogs she says that, "To an untrained human ear, it sounds much like a pant, 'hhuh, hhuh." When the recordings were analyzed she found that that this exhalation bursts into a broader range of frequencies than does regular dog panting. She confirmed the positive effects of this laugh sound in an experiment on 15 puppies, which romped for joy simply upon hearing the recorded canine laugh. More recently she was able to show that these same sounds helped to calm dogs in an animal shelter.
Simonet noticed that when she tried to imitate the laugh panting sounds of dogs it seemed to have a positive effect on the animals hearing it.
I must admit that I was a bit skeptical about the usefulness of humans making these dog laugh sounds. So I began to experiment, originally with my own dogs. My first attempts were not very successful, causing virtually no response or at best puzzled looks from my dogs. However I was eventually able to shape a set of sounds which reliably evoked interest on the part of my dogs. It required conscious monitoring to get the sound pattern right. For me, what seems to work the best is something like "hhuh-hhah-hhuh-hhah..." with the "hhuh" sound made with slightly rounded lips, while the "hhah" sound is made with a sort of open mouthed smiling expression. The sound has to be breathy with no actual voicing. Thus if you touch your throat while making this sound you should not feel any vibration. This caused my own dogs to sit up and wag their tails or to approach me from across the room.
Since these initial informal experiments I have extended my observations and tried using my human imitation of dog laughter sounds to calm worried, anxious and shy dogs in a dog obedience class and in other settings. It seems to help if you glance at the dog directly only for brief intervals alternating with glancing away. Also short quick side to side movements appear to help. It seems to work best in calming dogs that are moderately anxious or insecure. If the negative emotions experienced by the dog are too intense it does not seem to help. This is reminiscent of trying to calm humans. If they are moderately anxious introducing somehumor into the situation can be helpful and relaxing, while if they are in a state of panic your attempts might be viewed as actually laughing at their emotional state and may actually make things worse.