Section C Laughter is a fundamental part of everyday life. It is so common that we forget how strange-and important-it is. Indeed, laughter is a "speaking in tongues" in which we're moved by an unconscious response to social and linguistic cues. Stripped of its variation and nuance, laughter is a regular series of short vowel-like syllables usually transcribed as "ha-ha", "ho-ho" or "hee-hee". These syllables are part of the universal human vocabulary, produced and recognized by people of all cultures. Given the universality of the sound, our ignorance about the purpose and meaning of laughter is remarkable. We somehow laugh at just the right times, without consciously knowing why we do it. Most people think of laughter as a simple response to comedy, or a cathartic mood-lifter. Instead, after ten years of research on this little-studied topic, I concluded that laughter is primarily a social vocalization that binds people together. Students in my classes confirmed the social nature of laughter by recording the circumstances of their laughter in diaries. After excluding the effects of media, the fact was striking: Laughter was thirty times more frequent in social than solitary situation and it's a signal we send to others and it virtually disappears when we lack an audience. As anyone who has ever laughed at the sight of someone doubled over can attest, laughter is contagious. Because our laughter is under minimal conscious control, it is spontaneous and relatively uncensored. Contagious laughter is a compelling display of Homo sapiens, a social mammal. It strips away our outer layer of culture and challenges the hypothesis that we are in full control of our behavior. From these synchronized vocal outbursts come insights into the neurological roots of human social behavior and speech. The irresistibility of others' laughter has its roots in the neurological mechanism of laugh detection. The fact that laughter is contagious raises the intriguing possibility that humans have an auditory laugh detector-a neural circuit in the brain that responds exclusively to laughter. Once triggered, the laugh detector activates a laugh generator, a neural circuit that causes us in turn to produce laughter. Furthermore, laughter is not randomly speech. There is evidence of "the punctuation effect", the tendency to laugh almost exclusively at phrase breaks in speech. The pattern requires that speech has priority over laughter. Pain reduction is one of laughter's promising applications. Rosemary Cogan, Ph. D., a professor of psychology at Texas Tech University, found that subjects who laughed at a funny video or underwent a relaxation procedure tolerated more discomfort than other subjects. Humor may help soften intense pain and it may also help us cope with stress. In a study by Michelle Newman, Ph. D., an assistant professor of psychology at Pennsylvania State University, subjects viewed a film about three grisly accidents and had to narrate it either in a humorous or serious style. Those who used the humorous tone had the lowest negative effect and tension. However, a problem with these studies is that none of them separate the effects of laughter from those of humor. None allow for the possibility that presumed effects of laughter or humor may come from the playful setting associated with these behaviors. And none evaluate the uniqueness of laughter by contrasting it with other vocalizations such as shouting. Rigorous proof that we can reduce stress and pain through laughter remains an unrealized but reasonable prospect. While we wait for definitive evidence, it can't hurt-and it's certainly enjoyable-to laugh. Answer the following questions with the information given in the passage.

问答题 What does the author believe is the nature of laughter?

问答题 What surprising fact did the study reveal about the circumstances in which people laugh?

问答题 What fact does the passage reveal about laughter and speech?

问答题 What further studies are needed on laugher and pain reduction?

问答题 What does the passage mainly talk about?