人生樂觀還是悲觀由基因決定

FOR some people in this world, the glass always seems to be half-full. For others it is half-empty. But how someone comes to have a sunny disposition in the first place is an interesting question.

It has been known for a long time that optimists see the world selectively, mentally processing positive things while ignoring negative ones, and that this outlook helps determine their health and well-being. In recent years, it has also become clear that carriers of a particular version of a particular gene are at higher risk than others of depression and attempted suicide when they face traumatic events. The gene in question lies in a region of the genome that promotes the activity of a second gene, which encodes a protein called the serotonin transporter. Serotonin is a messenger molecule that carries signals between nerve cells, and it is known to modulate many aspects of human behaviour, although the details are complex and controversial. The transporter protein recycles serotonin back into the cell that produced it, making it available for reuse, but also reducing the amount in the junctions between cells and thus, it is presumed, the strength of the signal.

在這個世界上，對於一些人來說，玻璃杯裏的水似乎總是半滿。對於另外一些人來說，玻璃杯裏的水總是半空。但是樂觀者是如何首先獲得這種積極向上的天性的呢?這是個很有趣的問題。

長久以來人們知道，樂觀者們選擇性地看待這個世界，他們的心理處理那些積極的事情但是忽略那些消極的事情，人們還知道這種心態有利於樂觀者們的健康和幸福。最近人們還清楚地發現對於有些攜帶某種特別形式的某種特別基因的人，他們在面對創傷性事件面前更加容易患上抑鬱症，也更容易嘗試自殺。這種特別的基因位於人類基因組的某個區域，這個區域激活第二種基因，而這第二種基因對所謂的血清素傳輸子進行蛋白質編碼。血清素是一種信使分子，它傳輸神經細胞間的信號。人們還知道血清素調節人類行爲的許多方面，儘管其中的細節很複雜而且對其解釋也有爭議。傳輸蛋白把血清素“回收”到產生它的細胞，使其能重複利用，但是這也減少了細胞間的節點數量，因此人們也認爲減少了信號的強度。

It has looked increasingly likely, therefore, that genes—particularly those connected with serotonin—have a role to play in shaping a person’s outlook. So Elaine Fox and her colleagues at the University of Essex, in Britain, wondered whether genes play a part in the selective attention to positive or negative material, with consequent effects on outlook.

To find out, they took samples of DNA from about 100 people and then subjected these people to what is known as the dot-probe paradigm test to see how they reacted to different stimuli. In this test participants are briefly shown photographs that may be positive, negative or neutral in tone. They then have to press a keypad to indicate when a dot has appeared on the screen. It has been found by experience that the more distracting an image is, the longer a person takes to respond when the dot appears. That allowed Dr Fox and her team to discover how distracting particular people found particular images.

因此，人們越來越發現基因——特別是與血清素相關的基因很可能對人們形成“世界觀”有作用。所以來自英國埃塞克斯大學(University of Essex) 的Elaine Fox 和她的同事想知道基因是否在對積極或者消極事件的選擇性注意上起一定的作用，從而影響“世界觀”。

爲了找出答案，他們採集了大約100人的DNA樣品，然後對這些人進行所謂的點探測任務實驗，以便觀察他們對不同刺激的反應。在這個實驗中，實驗參與者們短暫地看一些照片，這些照片的“格調”可能是積極的、消極的或者中性的。然後當這些實驗參與者們在屏幕上看到一個點出現後，必須按一下鍵盤。經驗發現照片越是分散人的注意力，那麼當點出現在屏幕上後，人們就需要更長的時間做出反應。這就讓Fox博士和她的研究小組發現特定的人對特定的照片是如何被吸引的。

In a paper just published in the Proceedings of the Royal Society B they report that, sure enough, gene-related variation caused a bias in attention towards positive and negative material. Some people had two “long” versions of the promoter gene (one inherited from each parent), a combination that reduces the amount of serotonin in the junctions between nerve cells. These individuals were biased towards positive images and away from negative ones. By contrast, those who had either a long and a short version of the gene, or two short versions (and thus, presumably, more serotonin in the junctions), did not have such protective biases. In other words, the optimists really did see the world differently.

Rose-tinted spectacles may be good for one’s health, as these results fit in with wider ideas about how a tendency to look on the bright side of life is part of being resilient to stress. Those with short variants of this gene are expected to have an increased susceptibility to mood disorders following such stress. It is not all good news, though, for optimists. Because these results suggest that a person’s attitude to life is inherited, they serve as a stark warning to all buoyant optimists that trying to cheer the rest of the world up with nothing more than a smile and an effortlessly sunny disposition is doomed to failure.

在剛剛發表於《皇家學會學報B》(Proceedings of the Royal Society B)的文章中，他們報道說，與基因相關的變化肯定導致了人們對積極和消極事物注意力的偏愛。有些人具有兩個“長”版本的啓動子基因(遺傳自雙親)，這種組合減少了神經細胞節中血清素的含量。這些人偏愛積極的照片，而不喜歡消極的照片。相反，那些帶有一長一短，或者兩短“版本”啓動子基因的人就沒有這種保護性的偏愛，而這種基因組合可能使得神經節中的血清素含量更高。換句話說，樂觀者們真地是以不同的方式看世界的。

積極的眼光可能對人的健康有好處，這些結果也和大衆的觀點相吻合， 那就是經常看到生活陽光的一面會有助於應付壓力。而那些“短”版基因的人在這樣的壓力下可能更易受到情緒混亂的影響。然而，對於樂觀者們來說，並非一切都是好消息。因爲這些研究結果暗示一個人對待生活的態度可能來自於遺傳，這對所有的樂觀者們提供了一個嚴厲的警告：想僅僅依靠微笑和天生的積極性格讓整個世界都高興起來是註定不可行的。