Laughter as a scientific problem: An adventure in sidewalk neuroscience.

Laughter is a stereotyped, innate, human play vocalization that provides an ideal simple system for neurobehavioral analyses of the sort usually associated with such animal models as walking, wing-flapping, and bird song. Laughter research is in its early stages, where the frontiers are near and accessible to simple observational procedures termed "sidewalk neuroscience." The basic, nontechnical approach of describing the act of laughter and when humans do it has revealed a variety of phenomena of social and neurological significance. Findings include the acoustic structure of laughter, the minimal voluntary control of laughter, contagiousness, the "punctuation effect" that describes the placement of laughter in conversation, the dominance of speech over laughter, the role of breath control in the evolution of speech, the evolutionary trajectory of laughter in primates, and the role of laughter in human matching and mating. If one knows where to look and how to see, advances in neuroscience are accessible to anyone and require minimal resources.