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 disposition1 in the first place is an interesting question.
It has been known for a long time that optimists2 see the world selectively, mentally processing positive things while ignoring negative ones, and that this outlook helps determine their health and well-being3. In recent years, it has also become clear that carriers of a particular version of a particular gene4 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 molecule5 that carries signals between nerve cells, and it is known to modulate6 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 junctions7 between cells and thus, it is presumed, the strength of the signal.
It has looked increasingly likely, therefore, that genes8 -- 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 DNA9 from about 100 people and then subjected these people to what is known as the dot-probe paradigm10 test to see how they reacted to different stimuli11. In this test participants are briefly12 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.
In a paper just published in the Proceedings13 of the Royal Society B they report that, sur
e enough, gene-related variation caused a bias14 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 biased15 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 biases16. 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 variants17 of this gene are expected to have an increased susceptibility to mood disorders18 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 stark19 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 doomed20 to failure.
词汇表：
1 disposition     
n.性情，性格；意向，倾向；排列，部署
参考例句：
He has made a good disposition of his property.他已对财产作了妥善处理。
He has a cheerful disposition.他性情开朗。
2 optimists     
n.乐观主义者( optimist的名词复数 )
参考例句：
Even optimists admit the outlook to be poor. 甚至乐观的人都认为前景不好。 来自《简明英汉词典》
Optimists reckon house prices will move up with inflation this year. 乐观人士认为今年的房价将会随通货膨胀而上涨。 来自辞典例句
3 well-being     
n.安康，安乐，幸福
参考例句：
He always has the well-being of the masses at heart.他总是把众的疾苦挂在心上。
My concern for their well-being was misunderstood as interference.我关心他们的幸福，却被误解为多管闲事。
4 gene     
n.遗传因子，基因
参考例句：
A single gene may have many effects.单一基因可能具有很多种效应。
The targeting of gene therapy has been paid close attention.其中基因的靶向性是值得密切关注的问题之一。
5 molecule       
n.分子，克分子
参考例句：
A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈?f婘??妈?成的。
This gives us the structural formula of the molecule.这种方式给出了分子的结构式。
6 modulate       
v.调整，调节(音的强弱)；变调
参考例句：modulate
Please modulate the sound on the TV.请调节一下电视的音量。
This system could modulate the voice signal effectively.这个系统可以对语音信号进行有效的调制。
7 junctions       
联结点( junction的名词复数 )； 会合点； （公路或铁路的）交叉路口； （电缆等的）主结点
参考例句：
Metals which were mutually soluble would tend to give strong junctions. 可互溶的金属趋向于产生牢固的结合点。
Some adhering junctions are present as narrow bands connecting two cells. 有些粘附连接以一窄带的形式连接两个细胞。
8 genes     
n.基因( gene的名词复数 )
参考例句：
You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪
9 DNA     
(缩)deoxyribonucleic acid 脱氧核糖核酸
参考例句：
DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。

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