When audiences burst into applause they act as if "infected" by sound, say researchers.
Scientists studied clapping contagion in groups of university students listening to an oral presentation.
An individual's likelihood of starting to clap was found to increase in proportion to the number of other audience members already putting their hands together.
But it made no difference where members of the audience were seated. The source of the "infection" was sound, not the sight of other clapping hands.
Clapping lasted for an average of six seconds before it trailed off in a similar contagious way.
Mathematician Richard Mann, from Uppsala University in Sweden, and colleagues wrote in the Journal of the Royal Society Interface: "In an applause setting, each clap produced by an individual provides us with a time point at which he or she remains 'infected' by appreciation, and cessation of clapping denotes 'recovery'."
The lessons learned from audience applause could be applied to other forms of social contagion, said the scientists.