Passage 3



  Does play help develop bigger, better brains? Bryant Furlow investigates


  玩耍能否帮助大脑发育得更大更好?Bryant Furlow就此展开了调査。

  A 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.

  A玩耍是件严肃的事。孩子们沉溺在假想的世界中,狐狸幼崽儿嬉戏打闹,小猫玩线球,这些行为都不只是取乐而已。看上去玩耍是成人世界的辛苦工作到来之前,无忧无虑、精力充沛的消磨时光的方式,其实远非如此。首先,玩耍可能使动物们送命。比如,百分之八十的小海狗死亡都是因为玩耍中的小海狗没能看到接近的捕食者。玩耍也是相当消耗精力的。顽皮的小动物要花上百分之二三的精力来嬉戏打闹,而对于儿童而言,这个数字可以高达百分之十五。“就算只有百分之二三也是个不小的数目了。”Idaho大学的John Byers说道,“你很难发现动物们如此消耗精力。”Byers补充说。总有一定的原因使他们这么做。

  B 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.


  C 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.


  D 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.

  D接着,我们又有了技能训练假说。乍看上去,玩耍的小动物好像是在练习那些成年时必须的复杂动作。但是,更为仔细的观察表明,这种解释把问题简单化了。在某项研究中,California大学的行为生态学家Tim Caro观察了小猫的捕食游戏以及它们成年之后的捕猎行为。他发现,小猫玩耍的方式对成年后的捕猎技能并没有太大的影响。

  E 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.

  E今年早些时候,加拿大Lethbridge大学的Sergio Pellis公布说,哺乳动物的玩耍与他们大脑的大小往往成正比。在比较了十五种哺乳动物的测量数据之后,Sergio和他的研究小组发现,更多的玩耍会造就大一些的脑子(与身体大小比较而言),而且这个理论反过来也成立。Durham大学的Robert Barton认为,由于大一座的脑子比小一些的脑子对发育刺激更敏感,因此它们需要更多的玩耍来促进它们发育至成年期。他说:“我的结论是,玩耍与学习有关,也与大脑发育过程中环境资料的重要性有关。”

  F 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.


  G ‘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.’

  G“人们没有充分注意到玩耍激活了大脑多少部件。”Colorado大学的Marc Bekoff说。Becoff研究了玩要的小土狼,发现其中所涉及的行为显然比成年土狼的花样更多,更不可预测。他推断,这样的行为能激活大脑许多不同的部分。由于动物们在玩耍时行为总是迅速地变换,Becoff将玩耍比喻为一个行为万花筒。“他们会做出不同环境所需要的动作——捕猎,进攻,繁殖等,而他们正在发育的大脑获得了各种各样的刺激。”

  H 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.

  H大脑不仅比猜想中更多地参与玩耍,而且好像还能够激活更髙级的认知过程。“玩耍中有很多的认知成分。”Becoff指出。玩耍通常包括对玩伴的评估,互相依存的观念,以及恃殊标志及规则的使用。他认为玩耍会创造一个更具行为灵活性,在今后生活中更多学习潜力的大脑。这一观点得到了Gettysburg学院Stephen Siviy研究结果的支持。Siviy认为玩耍能够影响大脑中一种特殊化学物质的分泌,这种物质会刺激神经细胞生长。他被这种刺激可能达到的程度吓了一跳。“玩耍使一切都变得活泼起来。”通过使大脑中不常交流的部分产生联系,玩耍也许会提髙创造力。

  I 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?