这是为什么呢？格林有他自己的理论，其中的一条他总结为伍迪·艾伦的名言：“生活中80%的成功是自我表现。”
格林说：“这一点对于给小费来说也很重要。对于接你的出租车司机和为你服务的服务员，你不得不给一点额外的小费。如果他们不存在，你就得不到任何服务，所以我认为给小费一部分是因为他们的存在。”
格林解释说，既然每个人都会获得“因为存在”的那部分小费，所以小费在较小金额的消费中必然占较大的比例。
Americans Love Pets
Americans love pets.And it’s not just puppy love，either.Many pet owners treat their furry friends as part of the family.Sometimes they spice up their pets’lives with entertaining videos and amusing toys.If they have an eye for fashion，pet owners can dress their pets in stylish clothes.For special occasions，they can use canine perfume to make their dogs smell，well，less beastly.You might say Americans treat their pets like they treat their children—sometimes even better.
In America，there are more households with pets than those with children.At least 43percent of U.S.homes have pets of some sort.Exotic creatures，such as monkeys，snakes and even wolves，find a home with some Americans.More common pets include tropical fish，mice and birds.But the alltime favorites are cats and dogs，even at the White House.The Clintons’cat，Socks，has replaced the Bushes’dog，Millie，as reigning First Pet.Americans sometimes have strong feelings about whether dogs or cats make better pets.“Dog people”and “cat people”often enjoy friendly rivalries.
Leading a dog’s life in America isn’t such a bad thing.Many grocery stores sell gourmet pet foods to owners eager to please their pets.In Houston，Texas，dogs can have their dinner delivered to their homes，just like pizza.Welltodo canines can attend doggy daycare centers while their owners work.Pets can even accompany their owners on vacation.Fancy hotels are beginning to accommodate both man and beast.Furry guests at Four Seasons Hotels can enjoy gourmet meals served on fine china and sleep in soft beds.
Beneath the fluffy luxuries，there lies a basic American belief：Pets have a right to be treated well.At least 75animal welfare organizations exist in America.These provide care and adoption services for homeless and abused animals.Veterinarians can give animals an incredible level of medical care for an incredible price.To pay for the hightech health care，people can buy health insurance for their pets.And when it’s time to say goodbye，owners can bury their pets in a respectable pet cemetery.
The average American enjoys having pets around，and for good reason.Researchers have discovered that interacting with animals lowers a person’s blood pressure.Dogs can offer protection from burglars and unwelcome visitors.Cats can help rid the home of unwanted pests.Little creatures of all shapes and sizes can provide companionship and love.In many cases，having a pet prepares a young couple for the responsibilities of parenthood.Pets even encourage social relationships：They give their owners an appearance of friendliness，and they provide a good topic of conversation.
Pets are as basic to American culture as hot dogs or apple pie.To Americans，pets are not just property，but a part of the family.After all，pets are people，too.
美国人的宠物情结
美国人很爱宠物，而且这不只是一种不成熟的、短暂的爱。很多宠物的主人把这些毛茸茸的朋友当作家庭的一部分，有时候还为宠物准备娱乐用的录像带和玩具来增添它们生活的乐趣。如果宠物的主人具有流行的眼光，还会让他们的宠物穿上时髦的衣服。在特殊的场合里，甚至为宠物喷上狗儿专用的香水，让它们味道好闻一点，减少一些动物身上的味道。你也可以说，美国人待他们的宠物如同待他们的孩子一样——有时甚至更好。
在美国，有宠物的家庭比有孩子的家庭还多。至少百分之四十三的美国家庭有宠物，有些美国家庭养一些外国品种的动物，例如猴子、蛇、甚至狼；比较常见的宠物有热带鱼、老鼠和鸟。不过，一直广受欢迎的是猫和狗，连白宫也不例外。克林顿总统的猫——袜子，已经取代了布什的狗——米利，成为神气的“第一宠物”。美国人有时候很在乎到底最好的宠物是猫还是狗，“爱狗的人”和“爱猫的人”喜欢开玩笑地彼此争辩。
在美国，狗所过的生活并不坏，很多杂货店都卖有宠物美食，让主人可以讨好他们的宠物。在得克萨斯州的休斯敦市，狗儿还能享用专程送到家的晚餐，就跟比萨一样。家境富裕的狗儿在主人上班的时候可以去狗儿托育中心。宠物甚至可以和它们的主人一同去度假，高级饭店已经开始可以同时留宿人和宠物，这些毛茸茸的客人在四季饭店可以享用以精致瓷器盛装的美食，并在柔软的床上睡觉。
在舒适奢华的享受之下，其实存在着美国人的一种基本信念：宠物有受到妥善对待的权利。美国至少有七十五个动物福利组织，他们为流浪动物及被虐待动物提供照顾与领养的服务。兽医能提供给动物极好的医疗照顾——价格也极昂贵。若为了负担更先进的健康医疗照顾，人们可以为他们的宠物买健康保险。如果和宠物道别的时机到了，主人们可以为宠物买一块体面的墓地。
美国人一般都喜欢有宠物为伴，这是有原因的。研究人员发现，与动物为伍能够降低人的血压。狗能防止小偷及不受欢迎的访客。猫能帮忙清除家里讨人厌的害虫和有害的小动物。任何种类及大小的小宠物都能带给人们相伴与爱的感觉。很多时候，拥有一只宠物能帮助年轻夫妻作为人父母责任的准备。宠物甚至有助于人际关系：它们使主人们看起来更友善，并且也带给人们一个交谈的好话题。
宠物是美国文化中很基本的一部分，就如热狗和苹果派一样。对美国人而言，宠物不仅仅是他们所拥有的一样东西而已，它是家庭的一部分。毕竟，宠物也是“人”啊！
Ordering a Perfect Baby
“Egg Donor Needed.US 50，000Incentive.”This is a sample heading from one of the ads that has begun to appear at Ivy League schools such as Yale and Harvard.Although egg donation is not news，those intending to purchase human eggs have now gone beyond requesting a certain eye color to demanding Ivy League degrees.These potential buyers believe that raising the standard of their criteria will bring them a better baby.But does this ambition to purchase a genetic advantage for their children make them bad parents？
Couples who place these ads assume that if a young woman attends an Ivy League school，then she will likely pass on her academic ability to her offspring.This assumption disregards many other factors such as the genetic contribution of the sperm and the determining forces of our environment.Our lives are influenced，but not predetermined，by our genes.
One danger of ordering babies like televisions is that parents may have unreasonable expectations of their child.If the child doesn’t turn out the way the parents envisioned，how will he or she be treated？Good parents accept their children for whoever they happen to be—not just for attending Yale.
订做精品婴儿
“急征捐卵者，酬金5万美元。”这是一则广告的标题，最近开始出现在常春藤联盟名校的校园内，如耶鲁大学和哈佛大学。虽然卵子捐赠不是什么新鲜事，但卵子购买者指定的条件标准，已从眼睛的颜色提高到（捐卵者）需有常春藤盟校的文凭。这些潜在的买主相信，提高指定条件的标准，可以生出较优的婴儿。然而这种为孩子购买遗传优势的企图，是否让这些买主变成了不道德的父母？
刊登这则广告的夫妇认为，能读常春藤盟校的女生，很有可能将其在学术上的优秀能力遗传给后代。这种假设忽视了许多其他的因素，如精子遗传和后天环境的决定性影响。我们的人生会受到遗传基因的影响，但并不是完全由它决定的。
想像订购电视机一样量身订做婴儿的父母，会对孩子报有过高的期望。如果生出的孩子没有达到父母的期望，他们会怎么对待孩子？好父母应该能够接受自己的孩子，不管他是什么样子——当然也不能只因为他能上耶鲁大学。