一个人的笑容并不都是一个样子的。如果是自然的微笑,象在高兴时发自内心的笑,这种笑是对称的——在左右两颊均衡地展现出来。但如果是勉强的笑,那末嘴的左角比右角向上翘得稍高些,这种笑是不对称的。十多年来,一些精神病学者一直在研究分析面部肌肉对面部表情的影响。上述意见就是他们研究的结果。旧金山加利福尼亚大学的约瑟夫·哈格博士认为,做作的笑与自然的笑是由控制面部的两条不同的神经渠道引起的。哈格说,“我们可以肯定,勉强的笑与发自内心的笑是两种不同的神经细胞所引起的,但确切指 One’s smile is not always the same. If it is a natural smile, like a heartfelt smile when it is pleasing, the smile is symmetrical - displayed evenly on the left and right cheeks. But if grudging, then the left corner of the mouth up slightly higher than the right corner, this laugh is not symmetrical. For more than a decade, some psychiatrists have been studying the effects of facial muscles on facial expressions. The above opinion is the result of their research. Dr Joseph Haggard of the University of California, San Francisco, argues that laughed and natural laughs are caused by two different neural channels that control the face. Hage said, "We can be sure, barely laugh and heartfelt laughter is caused by two different types of nerve cells, but the exact means