科學證據表明你是一個樂觀或悲觀的人也許在你出生時就已經注定了。各位多愁善感時常情緒低落的同學，就面對現實吧。'Happiness' gene helps you look on the bright side

Positive people may owe their optimism to a gene variant that helps them dwell on the good and ignore the bad.

That's the conclusion from a study examining people's subliminal preferences for happy, neutral, and threatening images.

Volunteers who had inherited two copies of the "long" variant of 5-HTTLPR – a gene that controls transport of the mood-affecting neurotransmitter serotonin – showed clear avoidance of negative images, such as fierce animals, and a clear preference for positive ones, such as puppies. People with this variant combination are dubbed "LL" carriers.

The effect wasn't seen in volunteers with at least one version of the "short" variant of the same gene – these people showed no strong preference whatever the content of the images.

Time lapse

In repeated tests, the 97 volunteers had less than a second to identify dots hidden in one or other of a pair of adjacent images. Each pair contained a neutral image alongside one that was either positive or negative.

The researchers found that LL volunteers took 18.3 milliseconds longer on average to spot the dots in a negative rather than neutral image, suggesting a subliminal aversion to bad images.

Conversely, they noticed the dots 23.5 milliseconds sooner in the positive images, such as cuddly puppies, than in the neutral ones, suggesting they were subliminally drawn to them. "It sounds very small, but in terms of attentional time, it's consistent," says team leader Elaine Fox of the University of Essex in Colchester, UK.

Optimistic streak

Fox and her colleagues conclude that the LL volunteers may be primed to seek out positive events and ignore negative events.

Earlier studies had revealed a tendency for negativity and anxiety among individuals with at least one short variant of the gene, but the study is the first to reveal an optimistic streak in LL individuals.

"A number of mechanisms may contribute to this difference, and the authors have provided good evidence that attentional bias in the processing of emotional stimuli may be one of those mechanisms," says Turhan Canli, who has studied the same phenomenon at Stony Brook University in New York.

樂觀主義者之所以會樂觀向上也許是因為擁有能幫助他們凡事都向好的方面看且不去在意負面影響的基因。

通過一個檢測人在看到愉悅、中立和具威脅性的圖像時潛意識趨向性的實驗，人們得出了以上結論。

5-HTTLPR基因能夠控制影響人情緒的神經遞質血清素的傳遞。擁有兩對“長”變異5-HTTLPR基因的志愿者表現出對負面圖像的明顯排斥，如看到兇惡的動物，和對正面圖像的明顯喜愛，如看到小狗。帶有這種變異基因組合的人被稱為“LL”攜帶者。

在遺傳了至少一條“短”變異5-HTTLPR基因的志愿者中則看不到這種趨向性。這些人對不同圖片并沒有明顯的喜好。

時間差

在重復實驗中，97名志愿者需在不超過一秒的時間里分辨出隱藏在一對相鄰圖像中任意一張里的黑點。每一對圖像都包括一張中立的和一張或正面或負面的圖像。

研究發現，攜帶LL基因的志愿者找出負面圖像中的黑點比找出中立圖像中的黑點用時長18.3毫秒，表明這部分志愿者潛意識里不喜歡看負面的圖像。

相反地，這些志愿者找出正面圖像，如可愛的小狗，中的黑點比找出中立圖像中的黑點用時短23.5毫秒，表明他們潛意識里被正面圖像吸引。“看上去是很小的差別，但說到集中注意力的時間，這個研究結果是前后一致的。”英國Colchester埃塞克斯大學的研究小組組長Elaine Fox如是說。

樂觀的個性

Fox和她的同事們認為攜帶LL基因的志愿者也許天生就為尋找積極向上的事情，忽略有負面影響的事件做好準備了。

早先有研究表明擁有至少一條短變異5-HTTLPR基因的人個性有消極和抑郁的趨勢，不過這次的研究第一次揭示了樂觀個性和LL基因攜帶者之間的關系。

紐約Stony Brook大學的Turhan Canli，一位同樣研究這一現象的學者，說道“有許多運行機制都可能造成這種人個性上的差異，作者為我們提供了良好的證據來說明在處理情緒刺激時的注意力偏向性也許是其中一種運行機制。”