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经培育得到的脑容量更大的孔雀鱼，它们的内脏更小，繁育的后代也更少。
翻译：页一
不同动物间的对比表明，脑容量越大智力就越高，但它们消耗的能量也越多，还会导致许多其它后果。如今，科学家也观察到了同一物种中不同大脑尺寸的影响，他们的研究对象是孔雀鱼（guppy）。这项研究发表在《当代生物学》（Current Biology）杂志上。
瑞典研究人员培育了两组不同的孔雀鱼，一组大脑容量较大，另一组大脑容量较小。经过快速地改良培育，第一组鱼的脑容量比第二组大9%。
不出所料，当总共48条孔雀鱼接受学习测试时，大脑容量大的雌鱼表现得比大脑容量小的雌鱼更好。然而，两组鱼中雄鱼的得分基本相同，这可能是因为雌性孔雀鱼的视觉系统更适合研究中所用的智力测试。
但是更大的大脑容量也有不利的一面：这些更聪明的鱼内脏却更小，雄鱼小了20%，雌鱼小了8%；此外，大脑容量大的孔雀鱼后代数量也少了19%。为了给它们较大的大脑提供能量，这些聪明鱼做出的牺牲可能是进化上的劣势。“聪明反被聪明误”或许会变成现实。
Comparisons of different animals have shown that larger brains provide greater intelligence, but they also guzzle more energy and have other consequences. Now scientists have observed the effects of varying brain size within a single species: guppies. The work is in Current Biology. [Alexander Kotrschal et al., Artificial Selection on RelativeBrain Size in the Guppy Reveals Costs and Benefits of Evolving a LargerBrain]
Swedish researchers bred two different lines of guppies, selecting one for larger brains and one for smaller. The fish quickly modified until brains were nine percent larger in the big-brained line than in the other.
Not surprisingly, when 48 guppies were given learning tests, large-brained female fish outperformed small-brained females. However, males from both lines scored about the same, possibly because the female guppies' visual system was more suited to the type of intelligence test used.
But big brains also had a downside—the brainier fish had smaller guts, by 20 percent for males and 8 percent for females. Plus, the large-brained guppies produced 19 percent fewer offspring. In order to provide energy to their bigger brains, the egghead fish made sacrifices that may be evolutionary disadvantages. It may indeed be possible to be too smart for your own good.
—Sophie Bushwick
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