You’ve been known to snort, shed tears, spit fruity beverages out your nose and heave in uncontrollable fits of laughter—sometimes at the most inopportune moments. But what is laughter, really? Why do we laugh at things that aren’t even funny? And is it really the best medicine? To get to the heart of this universal human expression, Robert R. Provine, a professor of psychology and neuroscience at the University of Maryland, Baltimore County, studied 2,000 cases of naturally occurring laughter over a 10-year period. Laughter: A Scientific Investigation is Provine’s engaging and funny report on the evolution, health benefits, contagiousness, social role and neural mechanisms of laughter.