最新研究表明，智力进化是有限的，人类不可能拥有“超级大脑”。很多人对可以通过不同途径增强认识能力的药物非常感兴趣，但很自然就会问到，为什么我们不会变得更加聪明？这是因为evolutionary ceilings的存在。这正如身高八英尺可能很不错，但是心脏会因此无法将血液输送到大脑。

利他林和安非他命等药物能帮助人们更好地集中注意力。但是它们通常只对无法有效集中注意力的人们有所帮助，而那些能集中注意力的人们服用后会表现得更糟糕。更高的智力与心理和情绪也有关，患有创伤后紧张症的人无法忘记过去遭受的伤害。研究人员还举例说，德系犹太人的平均智商远高于一般的欧洲人种，但却受到“黑蒙性白痴病”这种遗传疾病的困扰。

A new research paper argues that there are limits to our mental evolution and that humans are not likely to ever develop a "supermind."

Studies of human evolution show that as natural selection, nutrition, and medical technology have improved, so has the upward trajectory of the human body. But Thomas Hill and Ralph Hertwig write in Current Directions in Psychological Science that our bodies may have their own self-imposed evolutionary ceilings.

"A lot of people are interested in drugs that can enhance cognition in various ways," Hill and Hertwig write. "But it seems natural to ask, why aren't we smarter already?"

According to Hill and Hertwig, humans have grown in height over time but because of the limited ability of the heart to pump blood to the brain, it would not be feasible for people to suddenly become eight feet tall. Likewise, sudden growths in brain capacity are most likely limited by our own evolutionary caps:

A baby's brain size is thought to be limited by, among other things, the size of the mother's pelvis; bigger brains could mean more deaths in childbirth, and the pelvis can't change substantially without changing the way we stand and walk.

Hill and Hertwig also argue that supposed cognitive-enhancing drugs like Ritalin and amphetamines may temporarily improve focus, but usually only work on people with "lower baseline abilities," and those who don't suffer from conditions like Attention Deficit Disorder actually perform at lower levels under their influence.

"If you have a specific task that requires more memory or more speed or more accuracy or whatever, then you could potentially take an enhancer that increases your capacity for that task," the two write. "But it would be wrong to think that this is going to improve your abilities all across the board."

And then there are the psychological and emotional issues associated with higher intelligence. Hill and Hertwig point to conditions like post traumatic stress disorder, a condition brought on when someone literally cannot forget a past trauma. They also point to the case of the Ashkenazi Jews, who possess IQ's significantly higher than the general population of Europe but also disproportionately suffer from Tay-Sachs disease.

"Memory is a double-edged sword," Hills says. "If something bad happens, you want to be able to forget it, to move on."

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(Agencies)

（中国日报网英语点津 Rosy 编辑）