A自然段

Playing is a serious business. Children engrossed in a make-believe world, fox cubs play-fighting or kittens teasing a ball of string aren’t just having fun. Play may look like a carefree and exuberant way to pass the time before the hard work of adulthood comes along, but there’s much more to it than that. For a start, play can even cost animals their lives. Eighty per cent of deaths among juvenile fur seals occur because playing pups fail to spot predators approaching. It is also extremely expensive in terms of energy. Playful young animals use around two or three per cent of their energy cavorting, and in children that figure can be closer to fifteen per cent. ‘Even two or three per cent is huge,’ says John Byers of Idaho University. ‘You just don’t find animals wasting energy like that,’ he adds. There must be a reason.

玩耍是一项严肃的事情。沉浸在幻想世界中的孩子，狐狸幼崽们的嬉戏或小猫戏弄一团线球并不仅仅是为了好玩。玩耍可能看起来像是在成年之前消磨时间的轻松愉快的方式，但实际上远不止如此。首先，玩耍甚至可能导致动物丧命。幼年毛皮海豹中80％的死亡是因为玩耍的幼崽们没有察觉到接近的捕食者。从能量的角度来看，玩耍也是非常昂贵的。活泼好动的幼年动物在嬉戏中消耗大约2到3％的能量，而在孩子们身上，这个比例可能更接近15％。“即使只有2到3％的能量消耗也是很大的，”爱达荷大学的约翰·拜尔斯指出。“你几乎找不到其他动物浪费能量的情况，”他补充道。必然存在着某种原因。

B自然段

But if play is not simply a developmental hiccup, as biologists once thought, why did it evolve? The latest idea suggests that play has evolved to build big brains. In other words, playing makes you intelligent.  Playfulness, it seems, is common only among mammals, although a few of the larger-brained birds also indulge. Animals at play often use unique signs – tail-wagging in dogs, for example – to indicate that activity superficially resembling adult behaviour is not really in earnest. A popular explanation of play has been that it helps juveniles develop the skills they will need to hunt, mate and socialise as adults. Another has been that it allows young animals to get in shape for adult life by improving their respiratory endurance. Both these ideas have been questioned in recent years.

但是，如果玩耍并不像生物学家曾经认为的那样仅仅是一种发展阶段的偶然现象，那么它为什么会进化出来呢？最新的想法认为，玩耍进化出来是为了培养大脑。换句话说，玩耍让人变聪明。看起来，好玩只在哺乳动物中普遍存在，尽管一些大脑较大的鸟类也会参与其中。玩耍的动物通常会使用独特的信号，比如狗摇尾巴，来表明这种看似成年行为实际上并不认真。关于玩耍的一个普遍解释是，它帮助幼崽们发展成为成年后需要的捕猎、交配和社交技能。还有一个解释是，它让幼年动物通过提高呼吸耐力来为成年生活做好准备。但是，近年来这些观点受到了质疑。

C自然段

Take the exercise theory. If play evolved to build muscle or as a kind of endurance training, then you would expect to see permanent benefits. But Byers points out that the benefits of increased exercise disappear rapidly after training stops, so any improvement in endurance resulting from juvenile play would be lost by adulthood. ‘If the function of play was to get into shape,’ says Byers, ‘the optimum time for playing would depend on when it was most advantageous for the young of a particular species to do so. But it doesn’t work like that.’ Across species, play tends to peak about halfway through the suckling stage and then decline.

以锻炼理论为例。如果玩耍进化为了增强肌肉或者作为某种耐力训练，那么你会期望看到永久的益处。但拜尔斯指出，增加运动量带来的好处在训练停止后很快就会消失，所以幼年玩耍带来的耐力提升在成年后就会消失。“如果玩耍的功能是为了好好锻炼身体，”拜尔斯说，“玩耍的最佳时间应该取决于对某个物种的幼崽来说最有利的时期。但事实并非如此。”各个物种中，玩耍的活跃程度往往在吸食阶段过了一半左右达到顶峰，然后逐渐减少。

D自然段

Then there’s the skills-training hypothesis. At first glance, playing animals do appear to be practising the complex manoeuvres they will need in adulthood. But a closer inspection reveals this interpretation as too simplistic. In one study, behavioural ecologist Tim Caro, from the University of California, looked at the predatory play of kittens and their predatory behaviour when they reached adulthood. He found that the way the cats played had no significant effect on their hunting prowess in later life.

然后是技能训练假设。乍看之下，玩耍的动物似乎在练习它们成年后所需的复杂动作。但仔细观察会发现，这种解释过于简单化。加利福尼亚大学的行为生态学家蒂姆·卡罗在一项研究中观察了小猫的捕食性玩耍以及它们成年后的捕猎行为。他发现，小猫的玩耍方式对它们日后的捕猎能力没有明显影响。

E自然段

Earlier this year, Sergio Pellis of Lethbridge University, Canada, reported that there is a strong positive link between brain size and playfulness among mammals in general. Comparing measurements for fifteen orders of mammal, he and his team found larger brains (for a given body size) are linked to greater playfulness. The converse was also found to be true. Robert Barton of Durham University believes that, because large brains are more sensitive to developmental stimuli than smaller brains, they require more play to help mould them for adulthood. ‘I concluded it’s to do with learning, and with the importance of environmental data to the brain during development,’ he says.

今年早些时候，加拿大莱斯布里奇大学的塞尔吉奥·佩利斯报告称，哺乳动物普遍存在大脑大小和好玩程度之间的强正相关关系。他和他的团队在比较了十五个哺乳动物目的测量数据后发现，相对于体型而言，大脑越大的动物越容易好玩。反之亦然。杜兰大学的罗伯特·巴顿认为，由于大脑对发育刺激更为敏感，相较于较小的大脑，大脑需要更多的玩耍来帮助塑造成年后的状态。“我得出结论是与学习以及大脑在发育过程中对环境数据的重要性有关，”他说。

F自然段

According to Byers, the timing of the playful stage in young animals provides an important clue to what’s going on. If you plot the amount of time a juvenile devotes to play each day over the course of its development, you discover a pattern typically associated with a ‘sensitive period’ – a brief development window during which the brain can actually be modified in ways that are not possible earlier or later in life. Think of the relative ease with which young children- but not infants or adults – absorb language. Other researchers have found that play in cats, rats and mice is at its most intense just as this ‘window of opportunity’ reaches its peak.

根据拜尔斯的说法，年幼动物玩耍时期的时机为我们提供了一个重要线索，揭示了其中的奥秘。如果你画出幼崽每天玩耍的时间随着其发育的变化过程，你会发现这个模式通常与“敏感期”有关，即一种短暂的发展窗口，在这个窗口期内，大脑可以发生无法在早期或晚期发生的方式进行修改。想想年幼儿童相对容易吸收语言知识（但婴儿和成年人不是），你就能明白这种情况。其他研究人员发现，猫、老鼠和小鼠的玩耍在“机遇之窗”达到最高峰时最为强烈。

G自然段

‘People have not paid enough attention to the amount of the brain activated by play,’ says Marc Bekoff from Colorado University. Bekoff studied coyote pups at play and found that the kind of behaviour involved was markedly more variable and unpredictable than that of adults. Such behaviour activates many different parts of the brain, he reasons. Bekoff likens it to a behavioural kaleidoscope, with animals at play jumping rapidly between activities. ‘They use behaviour from a lot of different contexts – predation, aggression, reproduction,’ he says. ‘Their developing brain is getting all sorts of stimulation.’

“人们对玩耍所激活的大脑部分没有给予足够的重视，”科罗拉多大学的马克·贝科夫说。贝科夫研究了玩耍中的小狼幼崽，并发现其中涉及的行为明显比成年动物更加多变和不可预测。他认为这种行为使大脑的许多不同部分都被激活。他将其比喻为一种行为万花筒，玩耍中的动物会在各种不同的背景下跳跃。“它们从很多不同的背景中借用行为——捕食、攻击、繁殖，”他说。“它们正在接受各种各样的刺激，去发展它们的大脑。”

H自然段

Not only is more of the brain involved in play than was suspected, but it also seems to activate higher cognitive processes. ‘There’s enormous cognitive involvement in play,’ says Bekoff. He points out that play often involves complex assessments of playmates, ideas of reciprocity and the use of specialised signals and rules. He believes that play creates a brain that has greater behavioural flexibility and improved potential for learning later in life. The idea is backed up by the work of Stephen Siviy of Gettysburg College. Siviy studied how bouts of play affected the brain’s levels of a particular chemical associated with the stimulation and growth of nerve cells. He was surprised by the extent of the activation. ‘Play just lights everything up,’ he says. By allowing link-ups between brain areas that might not normally communicate with each other, play may enhance creativity.

不仅大脑的更多部分参与到玩耍中，而且玩耍似乎也会激活更高级的认知过程。“玩耍中存在着巨大的认知参与，”贝科夫说。他指出，玩耍通常涉及到对玩伴的复杂评估、互惠思想以及使用专门的信号和规则。他认为，玩耍创造了一个行为更加灵活、学习潜力更强的大脑。史蒂芬·西维（Gettysburg College）的研究结果也支持这一观点。西维研究了玩耍时间对与刺激和神经细胞生长相关的一种化学物质在大脑中的水平的影响。他对这种激活的程度感到惊讶。“玩耍将所有东西都点燃了，”他说。通过允许大脑区域之间建立可能不会正常交流的联系，玩耍可能增强创造力。

I自然段

What might further experimentation suggest about the way children are raised in many societies today? We already know that rat pups denied the chance to play grow smaller brain components and fail to develop the ability to apply social rules when they interact with their peers. With schooling beginning earlier and becoming increasingly exam-orientated, play is likely to get even less of a look-in. Who knows what the result of that will be?