Ancient Greek philosopher Aristotle viewed laughter as “a bodily exercise precious to health.” But (1)_____ some claims to the contrary, laughing probably has little influence on physical fitness. Laughter does (2)_____ short-term changes in the function of the heart and its blood vessels, (3)_____ heart rate and oxygen consumption. But because hard laughter is difficult to (4)_____, a good laugh is unlikely to have (5)_____ benefits the way, say, walking or jogging does.
(6)_____, instead of straining muscles to build them, as exercise does, laughter apparently accomplishes the (7)_____. Studies dating back to the 1930s indicate that laughter (8)_____ muscles, decreasing muscle tone for up to 45 minutes after the laugh dies down.
Such bodily reaction might conceivably help (9)_____ the effects of psychological stress. Anyway, the act of laughing probably does produce other types of (10)_____ feedback that improve an individual’s emotional state. (11)_____ one classical theory of emotion, our feelings are partially rooted (12)_____ physical reactions. It was argued at the end of the 19th century that humans do not cry (13)_____ they are sad but that they become sad when the tears begin to flow.
Although sadness also (14)_____ tears, evidence suggests that emotions can flow (15)_____ muscular responses. In an experiment published in 1988, social psychologist Fritz Strack of the University of Würzburg in Germany asked volunteers to (16)_____ a pen either with their teeth—thereby creating an artificial smile—or with their lips, which would produce a(n) (17)_____ expression. Those forced to exercise their smiling muscles (18)_____ more enthusiastically to funny cartoons than did those whose mouths were contracted in a frown, (19)_____ that expressions may influence emotions rather than just the other way around. (20)_____, the physical act of laughter could improve mood.
