Though most of us spend a lifetime pursuing happiness, new research is showing that that goal may be largely out of our control. Two new studies this month add to a growing body of evidence that factors like genes and age may impact our general well-being more than our best day-to-day attempts at joy.

    In one study, researchers at the University of Edinburgh suggest that genes account for about 50% of the variation in people's levels of happiness - the underlying determinant being genetically determined personality traits, like "being sociable, active, stable, hardworking and conscientious," says co-author Timothy Bates. What's more, says Bates, these happiness traits generally come as a package, so that if you have one you're likely to have them all.

    Bates and his Edinburgh colleagues drew their conclusions after looking at survey data of 973 pairs of adult twins. They found that, on average, a pair of identical twins shared more personality traits than a pair of non-identical twins. And when asked how happy they were, the identical twin pairs responded much more similarly than other twins, suggesting that both happiness and personality have a strong genetic component. The study, published in Psychological Science, went one step further: it suggested that personality and happiness do not merely coexist, but that in fact innate personality traits cause happiness. Twins who had similar scores in key traits - extroversion, calmness and conscientiousness, for example - had similar happiness scores; once those traits were accounted for, however, the similarity in twins' happiness scores disappeared.

    Another larger study, released in January ahead of its publication in Social Science & Medicine this month, shows that whatever people's individual happiness levels, we all tend to fall into a larger, cross-cultural and global pattern of joy. According to survey data representing 2 million people in more than 70 countries, happiness typically follows a U-shaped curve: among people in their mid-40s and younger, happiness trends downward with age, then climbs back up among older people. （That shift doesn't necessarily hold for the very old with severe health problems.） Across the world, people in their 40s generally claim to be less happy than those who are younger or older, and the global happiness nadir appears to hit somewhere around 44.

    What happens at 44? Lots of things, but none that can be pinned down as the root cause of unhappiness. It's not anxiety from the kids, for starters. Even among the childless, those in midlife reported lower life satisfaction than the young or old, says study co-author Andrew Oswald, an economics professor at the University of Warwick in Britain. Other things that didn't alter the happiness curve: income, marital status or education. "You can adjust for 100 things and it doesn't go away," Oswald says. He and co-author David Blanchflower, an economist at Dartmouth College in New Hampshire, also adjusted their results for cohort effects: their data spanned more than 30 years, making them confident that whatever makes people miserable about being middle-aged, it isn't related, say, to being born in the year 1960 and growing up with that generation's particular set of experiences.

    At first glance, the new studies may appear at odds with some previous ones, largely because in happiness research, a lot depends on how you ask the question. Oswald and Blanchflower looked at responses to a sweeping, general question: "Taken all together, how would you say things are these days - would you say that you are very happy, pretty happy or not too happy?" （The wording changes slightly depending on where the survey was conducted, but the question is essentially the same.） In a 2001 study, Susan Charles at University of California, Irvine, measured something slightly different: changes in positive affect, or positive emotions, versus negative affect over more than 25 years. Charles found that positive affect stayed roughly stable through young adulthood and midlife, falling off a little in older age; negative affect, meanwhile, fell consistently with age.

    Charles thinks that feelings like angst, disgust and anger may fade because as we get older we learn to care less about what others think of us, or perhaps because we become more adept at avoiding situations we don't like. （The Edinburgh researchers, too, found that older study participants scored lower than younger ones on scales of neuroticism - worry and nervousness - and higher on scales of agreeableness.） Oswald chalks up the midlife dip in happiness shown in his study to people "letting go of impossible aspirations" - first, there's the pain of fading youth and the realization that we may never accomplish all that we had dreamed, then the contentment we gain later in life through acceptance and self-awareness. "When you're young you can't do that," Oswald says.

    An oft-cited finding from other happiness research suggests, however, that neither very good events nor very bad events seem to change people's happiness much in the long term. Most people, it seems, revert back to some kind of baseline happiness level within a couple years of even the most devastating events, like the death of a spouse or loss of limbs. Perhaps that kind of stability is due to heredity - those happiness-inducing personality traits that identical twins have been shown to share.

    Still, lack of control doesn't necessarily mean lack of joy. "The research also shows that most people consider themselves happy most of the time," says University of Edinburgh's Bates. "We're wired to be optimistic. Most people think they're happier than most [other] people." And even if you aren't part of that lucky majority, Bates says, there's always that other 50% of overall life satisfaction that, according to his research, is not genetically predetermined. To feel happier, he recommends mimicking the personality traits of those who are: Be social, even if it's only with a few people; set achievable goals and work toward them; and concentrate on putting setbacks and worries in perspective. Don't worry, as the saying goes. Be happy.

    雖然我們大多數人用一生來追尋幸福，但最新研究表明，這個目標很大程度上不受我們控制。本月公布的兩個新研究又一次證明，基因、年齡等因素對幸福感的影響，可能比我們每天作出的努力來得更加顯著。

    愛丁堡大學的研究者認為，基因決定著大約50%的人類幸福程度變量--這正是形成堅強性格特征的潛在決定因素，合作研究者Timothy Bates說，這些特征包括"社交活躍、積極、穩定、勤奮和盡責".他還表示，這些幸福的特質通常同時體現出來，因此如果你具備其中一個，則很可能也擁有全部特征。

    Bates和他的同事調查了973對成年雙胞胎后得出了這些結論。他們發現，一般來說，相比起非同卵的雙胞胎，一卵雙生的雙胞胎在性格上具有更多相同點。當被問到他們感覺有多快樂，一卵雙生雙胞胎的回答相似度比其他雙胞胎要高得多，這顯示出幸福感和性格有著強烈的基因成分。這個刊登在《心理科學》雜志上的研究進一步表明：性格和幸福感并非單純的共存關系，實際上正是天生的性格特質帶來了幸福感。在關鍵特征上--比如外向、平和、盡責等，擁有相似分數的雙胞胎，其幸福感指數也很相近；然而，一旦這些特質的分數不同，幸福感指數也隨之不盡相同。

    另一項大型研究結果在一月份發表，并于本月刊登在《社會科學和醫學》上。它顯示，無論人們個人的幸福感水平如何，我們都落入了一個更宏大的、跨文化的、全球性的快樂模式中。根據對超過70個國家，兩百萬人的調查，幸福感呈現出典型的U型曲線：在四十多歲的人群中，幸福感隨著年齡的增長而下降，然后在更年長的人群中又有所回升（這不包括那些遭受嚴重健康問題的人）.全世界范圍內，四十多歲的人群一般都比更年輕或更年長的人感到更少快樂，幸福低谷出現在大約44歲的年齡段。

    44歲發生了什么？許多事情，但沒有一樣能夠被視為不幸福的根源。研究者起先以為是來自對子女的憂慮，但不是。合作研究者，來自英國華威大學的經濟學教授Andrew Oswald表示，即使在沒有子女的中年人中，他們同樣比更年輕和更年長的人感受到更低的生活滿意度。其它事物，諸如收入、婚姻狀態和教育等均無法改變幸福曲線的走向。Oswald說："你可以調整100樣事情，但它就是不變。"他和另一位合作研究者，新漢普郡達特茅斯學院的經濟學家David Blanchflower, 因應"群效應"而調整了研究：他們的研究數據延續超過30年，使他們確信，無論是什么因素使人們在中年階段感到不快樂，都與其所處的特定時代無關，例如都出生在1960年并具有那一代人的獨特經歷。

    乍看起來，這些新研究與之前的很不一致，這大部分是因為在幸福感研究中，如何設問是很關鍵的。Oswald和Blanchflower提出的是一個宏觀的、全面性的"大問題":"總的來說，你怎么描述這些年來的各種事情？--你會說非常快樂、相當快樂還是不怎么快樂？"（用詞隨著調查地點的轉變有些許變化，但問題基本上是一樣的。）在2001年，加州大學爾灣分校的Susan Charles在研究中使用了稍不同的尺度：在超過25年里，積極的影響、積極的情緒的變化與消極的影響的對比。Charles發現積極的影響在青年和中年時代大致保持穩定，在更年長時稍微下跌；同時，消極影響隨著年齡持續地下降。

    Charles認為，像悲傷、厭惡和憤怒等情感逐漸減弱，是因為隨著年齡漸長，我們學會了不再那么在意別人的眼光，或者是因為我們更能夠審時度勢，避開不利的局面。（愛丁堡的研究者同樣發現，年長的調查對象在神經過敏程度上，如憂慮、緊張等，比年輕者分數較低；而在合作寬容程度上得分較高）.Oswald認為，研究顯示的中年幸福低谷是因為人們"不得不放棄無法實現的夢想".首先，人們需要面對青春消逝的無奈，并意識到自己可能永遠不能實現所有的夢想了。然后，當更年長一些之后，人們又通過寬容和自我覺醒獲得了滿足感。"當你年輕的時候你做不到這樣。" Oswald說。

    一個經常被引用的幸福感研究結果表明，極好和極壞的事件似乎并不能明顯改變人們在長期內的幸福感水平。多數人經歷過最慘痛的事情，例如配偶死亡或肢體殘疾等，之后的若干年內，他們的幸福感水平又回復到某個基線上。也許這種穩定性來自于遺傳--即那些能夠促進幸福感的性格特質，正如一卵雙生雙胞胎表現出來的那樣。

    當然，無法控制幸福感水平并不意味著失去歡樂。"研究同時顯示，多數人認為他們大多數時候都是快樂的。"愛丁堡大學的Bates說，"我們傾向于樂觀。多數受訪者認為他們比大多數其他人更快樂。"即使你不是那幸運的大多數，Bates說，根據他的研究，仍然有另外50%的生活滿意度并非由基因注定。要感受快樂，他建議仿效快樂者的性格特質：積極社交，即使只是和一些人；設定可達成的目標并努力去實現；注意消除自己觀念里的憂慮和挫折感。別擔心，正如俗語說的。快樂吧！