Applause in appreciation of a good performance follows a well-defined pattern of initial thunder turning into synchronized clapping, according to Barabasi. The synchronization process is relatively sudden, after which the individuals in the audience clap simultaneously and periodically, and the synchronization can disappear and reappear several times during the duration of the applause.

"The phenomenon is a wonderful expression of social self-organization," explains Barabasi, "and provides a human-scale example of the synchronization processes observed in numerous systems in nature, ranging from the synchronized flashing of the Southeast Asian fireflies to oscillating chemical reactions."

Other examples of spontaneous synchronization in biological and social systems include crickets synchronizing their chirps, pacemaker cells in the heart synchronizing their fire, and women living together for extended periods finding their menstrual cycles synchronized.

The results of the study of synchronized clapping include a number of unique features, however, that have not yet been observed in physical or biological systems, Barabasi says. "As a consequence," he says, "modeling the phenomenon of synchronized clapping may go beyond the description of this fascinating social self-organization and offer hints that could be useful in describing synchronization in other complex systems as well."

Barabasi and his team studied the mechanism and development of synchronized clapping with three experiments in which they performed a series of measurements that focused on both the collective aspects of the self-organization process as well as the behavior of individuals in the audience. They recorded, digitized and analyzed applause expressed for several theater and opera performances in Hungary and Romania. Recordings were made both by a microphone hanging from the ceiling of the concert hall and others placed near randomly selected individuals.

Well-controlled clapping experiments also were conducted using a group of 73 high school students. Additionally, one individual's clapping frequencies were studied for an entire week and analyzed. In all, 47 recordings were made and analyzed.

One conclusion the researchers made is that while the synchronization process increases the strength of the signal at the moment of the clapping, it leads to a decrease in the average noise intensity in the room. "This is rather surprising," says Barabasi, "since one would expect that the driving force for synchronization could be the desire of the audience to express its enthusiasm by increasing the average noise intensity." Analyzing the recordings of individuals clapping helped to solve this apparent anomaly.

The rhythmic applause is formed when individuals in the crowd lower their natural clapping frequency roughly to half. The result, says Barabasi, is that the congregate clapping loses volume. Individuals are not clapping any less loudly, but there is almost twice as much a pause between each clap in order to reach synchronization.

"The amazing interplay between unsynchronized and synchronized clapping is a consequence of this frustration," Barabasi says.

Individuals within the audience may be unsatisfied with the decrease in volume. Because they can only clap so hard, the way that individuals can increase the average noise intensity level is by speeding up the rhythm. With this effort, however, the synchronization is lost.

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