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How animals perceive time
動物如何感知時間？
Slo-mo mojo
慢動作的魔力
Small creatures with fast metabolisms see the world like an action replay
小生物可能擁有快速代謝系統，眼中的世界就想慢動作回放。
Sep 21st 2013 |From the print edition
FLIES live shorter lives than elephants. Of that there is no doubt. But from a fly’s point of view, does its life actually seem that much shorter? This, in essence, was the question asked by Kevin Healy of Trinity College, Dublin, in a paper just published in Animal Behaviour. His answer is, possibly not.
蒼蠅的壽命比大象短。這是毫無疑問的。但是從蒼蠅的角度來說，它的生命真的有那么短暫嗎？這是都柏林圣三一學院的Kevin Healy在《動物行為》上發表的論文中提出的問題的本質所在。他的回答可能是否定的。
Subjective experience of time is just that—subjective. Even individual people, who can compare notes by talking to one another, cannot know for certain that their own experience coincides with that of others. But an objective measure which probably correlates with subjective experience does exist. It is called the critical flicker-fusion frequency, or CFF, and it is the lowest frequency at which a flickering light appears to be a constant source of illumination. It measures, in other words, how fast an animal’s eyes can refresh an image and thus process information.
對時間的主觀經驗就是主觀的。即使是能與彼此交談對照時間的人類也不能確定他們跟別人的經驗相同。但是，客觀的測量與主觀的經驗確實有關系。這就是所謂的臨界閃爍融合頻率，簡稱CFF，這是閃爍的光作為照明固定光源的最低頻率。換句話說，測量動物眼睛刷新圖像的速度然后處理信息。
For people, the average CFF is 60 hertz (ie, 60 times a second). This is why the refresh-rate on a television screen is usually set at that value. Dogs have a CFF of 80Hz, which is probably why they do not seem to like watching television. To a dog a TV programme looks like a series of rapidly changing stills.
對人類來說，平均的CFF是60赫茲（即，每秒六十次）。這是通常設置的電視屏幕刷新率。狗狗眼睛的刷新率是80赫茲，這可能是它們不看電視的原因。對狗來說，電視節目看起來像一系列快速變化的幻燈片。
Having the highest possible CFF would carry biological advantages, because it would allow faster reaction to threats and opportunities. Flies, which have a CFF of 250Hz, are notoriously difficult to swat. A rolled up newspaper that seems to a human to be moving rapidly appears to them to be travelling through treacle.
有最快速的CFF會擁有生物學優勢，因為這意味著面對威脅或者機會時會有更快的反應速度。蒼蠅的CFF是250赫茲，很難被拍死。在人類看來迅速落下的一卷報紙在蒼蠅看來就想是慢動作。
Mr Healy reasoned that the main constraints on an animal’s CFF are its size and its metabolic rate. Being small means signals have less far to travel in the brain. A high metabolic rate means more energy is available to process them. A literature search, however, showed that no one had previously looked into the question.
Healy先生推斷，動物CFF的主要限制來自于其體型及其新陳代謝速度。體型小意味著大腦中信號傳遞速度快。高代謝率意味著更多的能量處理信息。然而，一個文獻檢索顯示之前沒人研究過這個問題。
Fortunately for Mr Healy, this search also showed that plenty of people had looked at CFF in lots of species for other reasons. Similarly, many other people had looked at the metabolic rates of many of the same species. And size data for species are ubiquitous. All he had to do, therefore, was correlate and repurpose these results. Which he did.
幸運的是，對Healy先生來說，很多人為了別的原因也研究了許多物種的CFF。同樣的，許多人也研究了許多上述物種的新陳代謝速率。物種體型大小的數據到處都是。這么一來，他需要做的就是關聯并重新利用這些結果。他這么做了。
To simplify matters he looked only at vertebrates—34 species of them. At the bottom end of the scale was the European eel, with a CFF of 14Hz. It was closely followed by the leatherback turtle, at 15Hz. Tuataras clocked in at 46Hz. Hammerhead sharks tied with humans, at 60Hz, and yellowfin tuna tied with dogs at 80Hz. The top spot was occupied by the golden-mantled ground squirrel, at 120Hz. And when Mr Healy plotted his accumulated CFF data against both size and metabolic rate (which are not, it must be admitted, independent variables, as small animals tend to have higher metabolic rates than large ones), he found exactly the correlations he had predicted.
為了簡化問題，他只看34種脊柱動物。CFF最低的是歐洲鰻鱺，只有14赫茲。緊隨其后的是棱皮龜，有15赫茲。錘頭鯊跟人類一樣，是60赫茲，黃鰭金槍魚跟狗一樣是80赫茲。最高的是地鼠，有120赫茲。當Healy先生將他的CFF數據跟體型和新陳代謝速率聯系起來，他發現了相關性完全符合其預測。（必須承認，體型和新陳代謝速率不是獨立的變量，小動物的新陳代謝速率比大型動物更快）
The upshot is that his hypothesis—that evolution pushes animals to see the world in the slowest motion possible—looks correct. Flies may seem short-lived to people, but from a dipteran point of view they can thus live to a ripe old age. Remember that next time you try (and fail) to swat one.
他的假設是進化可能讓動物更慢的速度看世界，結果看起來這個假設是對的。蒼蠅對人類來說似乎很短命，但是從蒼蠅的角度來說，它們能活得很長。記得下次拍死一個，可能拍不到哦。
