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.
You cite a study of the Ashkenazi Jews to illustrate this.
Research published in 2005 by Gregory Cochran and his co-authors suggests that the increased intelligence in the Ashkenazi is associated with a similar rise in specific neural disorders. In other words, in this case, increasing human intelligence appears to have arisen with a cost in cognitive diseases specifically associated with increased intelligence.
Can you talk to me about the Flynn effect?
The Flynn effect is the observation that, if you look at measures of IQ, people appear to be improving over about the past 100 years. There are many potential explanations. People might be healthier now than they were 100 years ago. There might be more emphasis on people doing well on intelligence tests. There are studies that suggest major improvements are in the lower portion of the population, which is consistent with our idea that some people are as smart as they are going to get. But the Flynn effect is unlikely to be an evolutionary phenomenon; the conditions are just not right for human evolution on this time scale.
So it is a bell-curve distribution that is shifting to the right?
Exactly, it's just kind of squeezing up against a wall.
Does that suggest some of us are reaching the upper limits of human intelligence?
That's a tricky thing to say. There are many ways to be smart. One reason why we may be smarter now is because we are better at distributed cognition. I can offload information on to external environments such as my computer, or a book, or even other people in my social network. And so long as we keep developing better means of distributing our cognition, chances are our efficiency and speed in processing information are going to increase.
Does that mean people at the lower end should be taking mind-enhancing drugs?
This might help some people with clinical disabilities to lead a normal life. But in many cases we should also be asking how we might change their external environment to improve, for example, their learning abilities. Pharmaceutical interventions are appealing because they seem so simple, but they are rarely as simple as they appear. Moreover, it's clear that we have hardly touched the surface of investigating educational or environmental enhancements.