The researchers found that the recordings led to a higher number of play among the birds, and for a longer period of time than observed when they had not heard the stimulus. Scientists know that play vocalisation in some species can act as a form of emotional contagion.
The study, published today in Current Biology, found a certain "play call" spurred other kea to engage in playful behaviour, even if no other birds had been playing.
Doing so revealed that some birds began to spontaneously play upon hearing the play call.
"Further research is needed to look for other effects the play call might have that parallel other effects of human laughter", he says.
"Upon hearing the play call, many birds did not join in play that was already underway, but instead started playing with other non-playing birds, or in the case of solitary play, with an object or by performing aerial acrobatics", the researchers point out.
And, while they note comparisons to humans may be somewhat anthropomorphic, Schwing says that 'If animals can laugh, we are not so different from them'. After analysing the kea's full vocal repertoire, Schwing and colleagues noticed the play call was linked to playful behaviour. It also sounds remarkably like a laugh.
As a control, they also played recordings of the South Island robin. But to show whether actual emotions are triggered in keas by the "laughter" you would have to "find some way of measuring the emotional state of both the callers and listeners".
The parrots soared after one another in aerobatic loops, exchanged foot-kicking high fives in mid-air and tossed objects to each other, in what seems to be emotionally contagious behaviour.
Raoul Schwing of the University of Veterinary Medicine in Vienna, Austria, and his team played 5-minute recordings to gatherings of between two and a dozen wild keas on a mountainside of New Zealand's Arthur's Pass National Park, on the southern island.
It means that humans and their closest relatives might not be the only species capable of emotional contagion spread by sound. "These instances suggest that kea weren't "invited" to play, but this specific call induced playfulness, supporting the hypothesis that play vocalizations can act as a positive emotional contagion".
Play is thought to strengthen bonds between social animals, which has benefits such as food sharing.