Why Isn't Human Intelligence Evolving Faster?

Thomas Hills is an associate professor of psychology at Warwick University. Along with Ralph Hertwig from Basel University he recently published a paper entitled "Why Aren't We Smarter Already: Evolutionary Trade-Offs and Cognitive Enhancement".

Why did you embark on this project?

I study the evolution of cognition. There is a growing interest in drug-enhancements for cognitive abilities, such as Ritalin and modafinil. Drugs like these are being used in many different places, like the military and education. So the question is, if these abilities are so great, why don't people already them? Typically, in evolutionary theory, if you want to ask why a fish doesn't swim faster, or why a bird can't see farther, the answer is there are trade-offs. The natural question is: what are the trade-offs for cognition and intelligence?

So you're asking why we haven't evolved to be more intelligent?

Exactly. And the evolutionary answer is that the costs are too high.

Doesn't education increase our intelligence?

Sure. We aren't suggesting that you can't read a book and get smarter; you can. We know from countless studies that if you give kids access to more resources, and you give them a better learning environment, they'll become smarter individuals. Our focus is on the increase in intelligence over evolutionary time, and, specifically, cognitive skills like memory and focus. More memory and focus are not necessarily better. You may not want to be so focused that you don't hear someone yelling "Look out!", or have such a perfect memory that you can instantly relive the pain you've felt at any point in your lifetime.

So, what are the downsides of highly developed cognitive skills?

There are two kinds, and we classify them as "within-domain" and "between-domain" trade-offs. Within-domain refers to cases, for example, where too little or too much focus creates a disadvantage. For instance, if you are pursuing someone you want to marry, and it's not working out, you need to know when to give up. If you are pursuing a particular objective that takes time to accomplish, then you have to know when to carry on.

A between-domain trade-off is what happens in the situation where you get individuals who appear to be exceptional in one domain and simultaneously show deficits in other domains. A classic example is the idiot savant. For example, a person might be able to count hundreds of matches that have been dropped on the floor but can't hold a conversation. Research has shown that you can turn off particular areas of the brain and turn people into these kinds of savants. Now the question is: do you want the skills of the savant?

Even in adult learning, studies by Eleanor Maguire on London taxi-drivers' enhanced spatial awareness noted that it comes with poorer performance in other areas. So they become smarter in one place while losing abilities in other domains. Brains seem to make interesting trade-offs.

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