Dogs sometimes pant in a manner that sounds like a human laugh. By analyzing the pant using a sonograph, this pant varies with bursts of frequencies. When this vocalization is played to dogs in a shelter setting, it can initiate play, promote pro-social behavior, and decrease stress levels. One study compared the behaviour of 120 dogs with and without exposure to a recorded “dog-laugh”. Playback reduced stress-related behaviors, increased tail wagging, the display of a “play-face” when playing was initiated, and pro-social behavior such as approaching and lip licking.
Source: Ultra Facts