The question of whether animals experience emotions and behaviors akin to our own has long captivated human curiosity. While not precisely identical to human laughter, many species exhibit distinct vocalizations and body language during playful interactions that scientists refer to as “laughter-like” behaviors. These expressions offer a window into the rich social lives of animals, suggesting a shared evolutionary heritage for positive communication.
Understanding Laughter in Animals
From a scientific standpoint, “laughter” in the animal kingdom is characterized by specific vocalizations, facial expressions, and body movements primarily observed during play. Unlike human laughter, it serves as a crucial signal during social interactions, not necessarily tied to humor or amusement. Researchers identify these behaviors by observing animals in playful contexts, noting sounds distinct from other forms of communication, such as alarm calls or distress signals. These vocalizations often involve a rapid alternation between inhalations and exhalations, resembling the breathy sounds of human laughter.
Scientists also analyze the acoustic properties of these sounds, looking for patterns like noisiness or tonality, pitch, length, and rhythm. The context in which these sounds occur is equally important; if they consistently appear during playful wrestling, chasing, or tickling, they are considered analogous to laughter. This approach helps distinguish play signals from other vocalizations and provides insight into animal emotional states.
The Laughter Chorus: Animals That Exhibit Playful Vocalizations
A comprehensive review of scientific literature found vocal play signals in at least 65 species, primarily mammals, but also a few bird species. Chimpanzees produce “pant-hoots” during play, breathy vocalizations from both inhalation and exhalation. These sounds are often accompanied by a “play face,” where their mouth is open but teeth are not shown.
Bonobos, closely related to chimpanzees, also vocalize during play or when tickled. Their vocalizations tend to be higher-pitched and more melodic compared to the lower, more guttural pant-hoots of chimpanzees. Gorillas also produce chuckles during play, often with a similar open-mouthed “play face.”
Beyond primates, rats exhibit laughter-like behaviors in the form of high-frequency ultrasonic chirps, typically around 50 kHz, which are inaudible to the human ear. These chirps are emitted when rats are tickled or play, and rats producing more chirps tend to play more. Dogs also display a form of laughter through breathy, panting sounds that vary with bursts of frequencies. When these sounds are played back to other dogs, they can encourage play, promote positive social behavior, and reduce stress.
Some bird species, such as the Australian magpie and kea parrot, also vocalize during play. When recordings of kea parrots’ warbling laughter were played through speakers, other keas would spontaneously begin to play.
The Role of Laughter in Animal Social Life
These laughter-like vocalizations and actions serve significant functions in animal social lives. Play signals, including these sounds, are crucial for communicating intentions during playful interactions. They help clarify that behaviors, which might otherwise appear aggressive or threatening, are indeed part of play and not a genuine attack. For example, a play-bow in dogs or a specific vocalization can signal “I’m just playing,” preventing misunderstandings that could lead to actual conflict.
Beyond preventing escalation, these vocalizations facilitate social bonding within animal groups. They act as an invitation to play, encouraging interaction and strengthening relationships between individuals. The ability to communicate play intention allows animals to engage in complex social play, vital for developing social skills such as cooperation and conflict resolution. Hearing laughter-like sounds can also induce positive emotional states, as seen in bonobos who become more optimistic after hearing the giggles of their companions. This suggests that the emotional contagion of laughter has deep evolutionary roots.
From an evolutionary perspective, these communicative play behaviors offer advantages by fostering social cohesion and allowing young animals to practice essential skills in a safe environment. Play helps animals develop motor skills, cognitive abilities, and social competence without the risks associated with real-life situations. The presence of laughter-like vocalizations across a wide range of species underscores their importance in mediating social interactions and promoting healthy development.