大黄蜂能否感受到像快乐一样的情绪?这或许看上去是不可能的，但蜜蜂的确会表现出悲观情绪，小龙虾也会经历焦虑。

科学家训练24只大黄蜂通过金属圆筒进入一个密闭室，以探究它们是否拥有类似于正面情绪的感觉。在密闭室中，大黄蜂面对一个拥有4根管子的墙壁。每根管子被贴上蓝色或者绿色的标签。大黄蜂通过训练得知，如果它们进入贴有绿色标签的管子，便不会获得奖励，只能得到水。不过，贴有蓝色标签的管子通向浓度为30%的糖溶液。

随后，大黄蜂接受了一项模糊测试，即管子没有被明确标记成蓝色或绿色。在这项测试中，随着大黄蜂进入通往密闭室的金属圆筒，有一半获得了一滴浓度为60%的糖溶液，而另一半未获得奖励。享受到糖溶液招待的蜜蜂在决定进入标记模糊不清的管子时花费了更少时间。这表明，甜点让它们对自己将要发现什么感到乐观。研究人员在日前出版的《科学》杂志上报告了这一成果。他们表示，吃甜食让人们感到快乐，而这种感觉会让人们在诸如赌博等模糊不明的状况下作出乐观的选择，就像蜜蜂一样。

其他实验则表明，这些昆虫不只是因“糖衣炮弹”而变得更加兴奋或活跃。相反，这种招待会诱导产生一种积极情绪，从而影响它们在其他状况下的行为。例如，和对照组相比，吃到甜食的蜜蜂在被暂时捉住并在模拟捕食者蟹蛛发起攻击的陷阱中被轻轻挤压后，会以更快的速度返回觅食。科学家还通过喂食蜜蜂一种堵塞大脑奖励中心的多巴胺抑制剂，终止了它们的乐观行为。

乐观是人类情绪的一部分，而在蜜蜂中发现乐观情绪，让科学家自身对这种感觉拥有漫长的进化史并且可能在很多动物中发现它感到乐观。

原文摘要：Can bumble bees feel something like happiness? It might seem unlikely, yet honey bees exhibit pessimism and crayfish can experience anxiety. To find out whether bumble bees have something akin to positive emotions, scientists trained 24 of the insects to enter a closed chamber via a metal cylinder. Inside, they faced a wall with four tubes. One was marked with either a blue or green tag. The bees learned that if they entered the green-tagged tube, they would get no reward—only water. But the blue-tagged tube led to a 30% sugar solution. They were then given an ambiguous test, wher the tube wasn’t clearly marked blue or green. In this test, as the bees entered the metal cylinder leading to the chamber, half received a droplet of a 60% sugar solution; the other half did not receive a reward. The sugar-treated bees took less time to decide to enter the ambiguously marked tube, suggesting that the sweet treat had led them to be optimistic about what they would find, the researchers report today inScience. Eating sweet food makes people happy, they note. And that feeling leads us to make optimistic choices in ambiguous situations, such as gambling—just like the bees. Other experiments showed that the insects weren’t merely more excited or active because of the sugar hit; instead, the treat induced a positive feeling that affected their behavior in other situations. For instance, the sugared-up bees returned to foraging faster after being momentarily caught and lightly squeezed in a trap that simulated a predatory crab spider’s attack than did the control bees. The scientists also ended the bees’ optimistic behaviors by giving them a dopamine inhibitor, which blocks the brain’s reward center. Optimism is part of human emotions, and finding it in bees makes the scientists themselves optimistic that the feeling has a long evolutionary history and is likely found in many animals.