Reasoning about probabilities is something humans can't always manage especially well, but it's clearly a skill we're capable of. In the wider world of animals, however, there are very few species we can say are able to make choices based on probabilities. So far, the only animals that have demonstrated the ability to make choices based on statistics are our fellow primates and the kea, an alpine parrot from New Zealand.

关于概率的推理，人类并不总是能够处理得特别好，但这显然是我们能够做到的一项技能。然而，在更广阔的动物世界里，我们可以说很少有物种能够根据概率做出选择。到目前为止，唯一能够根据统计数据做出选择的动物是我们的灵长类动物和kea，一种来自新西兰的高山鹦鹉。

All the species where this ability had been seen have a large brain relative to their body size, a feature that is associated with many advanced cognitive capabilities. So it was reasonable to conclude that statistical reasoning required some significant mental horsepower. But a study released on Thursday indicates that managing probabilities may be more widespread than we think since an animal with a relatively small brain—the giraffe—is apparently capable of it.

所有具有这种能力的物种都有一个相对于身体大小的大大脑，这一特征与许多高级认知能力有关。因此，我们可以合理地得出结论，统计推理需要一些强大的脑力。但周四发布的一项研究表明，管理概率的范围可能比我们想象的要广泛，因为长颈鹿这种大脑相对较小的动物显然有这种能力。

Reasoning based on probability and statistics sounds complicated, but we do it all the time. We weigh the likelihood of various factors when deciding what to bet in poker or which route to take on a commute. We're not always good about it; if we were, we'd freak out more about driving than we do about air travel. But the capacity to do so is there.

基于概率和统计的推理听起来很复杂，但我们一直在这样做。当我们决定在扑克中下什么赌注或选择通勤路线时，我们会权衡各种因素的可能性。我们并不总是擅长于此;如果是的话，我们对开车会比乘飞机更害怕。但这样做的能力是存在的。

The ability is also distinct from basic numeracy. When we choose which checkout line to commit to at the grocery store, we're typically just counting the number of people in each line, not weighing any sort of probability. One of the challenges of doing this sort of behavioral science with animals is distinguishing between probabilistic reasoning and basic numerical abilities.

这种能力也不同于基本的计算能力。当我们在杂货店选择哪条结账线时，我们通常只是计算每条线的人数，而不是权衡任何可能性。用动物做这种行为科学的挑战之一是区分概率推理和基本的数字能力。

Behavioral scientists seem to have settled on an approach where they start with a mixture of things the animal desires along with items they're indifferent to and vary the number and ratio of both of them. In the case of giraffes, this means giving them mixtures of carrots or zucchini—given the choice, they'll go for the carrots every time.

行为科学家似乎已经确定了一种方法，他们从混合动物渴望的东西和它们不感兴趣的东西开始，并改变两者的数量和比例。以长颈鹿为例，这意味着给它们胡萝卜或西葫芦的混合物——如果有选择的话，它们每次都会选择胡萝卜。

For the experiment, the researchers would show the animals tubs with mixtures of the two vegetables, then grab a single item from each without the giraffe being able to see what is in each hand. The animal would then gesture to one of the hands and receive whatever food item it held. For the basic test, the researchers had two tubs: one that contained 20 carrots and 80 pieces of zucchini and another that contained 80 carrots and 20 pieces of zucchini.

在实验中，研究人员会向长颈鹿展示两种蔬菜的混合物，然后在长颈鹿看不见每只手里拿着什么的情况下，从每只手里抓一个东西。然后，动物会向其中一只手做手势，并接受它手中的任何食物。在基本测试中，研究人员有两个桶:一个装有20根胡萝卜和80块西葫芦，另一个装有80根胡萝卜和20块西葫芦。

All four of the tested giraffes immediately figured this one out. In the first round of 20 tests, each was able to choose the hand that had a higher probability of holding a carrot at least 17 times.

所有四只接受测试的长颈鹿都立刻明白了这一点。在第一轮的20次测试中，每只长颈鹿都至少有17次能够选择更有可能拿着胡萝卜的手。