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How animals perceive time
动物如何感知时间？
Slo-mo mojo
慢动作的魔力
Small creatures with fast metabolisms see the world like an action replay
小生物可能拥有快速代谢系统，眼中的世界就想慢动作回放。
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.
苍蝇的寿命比大象短。这是毫无疑问的。但是从苍蝇的角度来说，它的生命真的有那么短暂吗？这是都柏林圣三一学院的Kevin Healy在《动物行为》上发表的论文中提出的问题的本质所在。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.
对时间的主观经验就是主观的。即使是能与彼此交谈对照时间的人类也不能确定他们跟别人的经验相同。但是，客观的测量与主观的经验确实有关系。这就是所谓的临界闪烁融合频率，简称CFF，这是闪烁的光作为照明固定光源的最低频率。换句话说，测量动物眼睛刷新图像的速度然后处理信息。
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.
对人类来说，平均的CFF是60赫兹（即，每秒六十次）。这是通常设置的电视屏幕刷新率。狗狗眼睛的刷新率是80赫兹，这可能是它们不看电视的原因。对狗来说，电视节目看起来像一系列快速变化的幻灯片。
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会拥有生物学优势，因为这意味着面对威胁或者机会时会有更快的反应速度。苍蝇的CFF是250赫兹，很难被拍死。在人类看来迅速落下的一卷报纸在苍蝇看来就想是慢动作。
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先生推断，动物CFF的主要限制来自于其体型及其新陈代谢速度。体型小意味着大脑中信号传递速度快。高代谢率意味着更多的能量处理信息。然而，一个文献检索显示之前没人研究过这个问题。
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.
幸运的是，对Healy先生来说，很多人为了别的原因也研究了许多物种的CFF。同样的，许多人也研究了许多上述物种的新陈代谢速率。物种体型大小的数据到处都是。这么一来，他需要做的就是关联并重新利用这些结果。他这么做了。
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.
为了简化问题，他只看34种脊柱动物。CFF最低的是欧洲鳗鲡，只有14赫兹。紧随其后的是棱皮龟，有15赫兹。锤头鲨跟人类一样，是60赫兹，黄鳍金枪鱼跟狗一样是80赫兹。最高的是地鼠，有120赫兹。当Healy先生将他的CFF数据跟体型和新陈代谢速率联系起来，他发现了相关性完全符合其预测。（必须承认，体型和新陈代谢速率不是独立的变量，小动物的新陈代谢速率比大型动物更快）
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.
他的假设是进化可能让动物更慢的速度看世界，结果看起来这个假设是对的。苍蝇对人类来说似乎很短命，但是从苍蝇的角度来说，它们能活得很长。记得下次拍死一个，可能拍不到哦。
