Human minds have hit an evolutionary "sweet spot" and - unlike computers - cannot continually get smarter without trade-offs elsewhere, according to research by the University of Warwick.

Researchers asked the question why we are not more intelligent than we are given the adaptive evolutionary process. Their conclusions show that you can have too much of a good thing when it comes to mental performance.

The evidence suggests that for every gain in cognitive functions, for example better memory, increased attention or improved intelligence, there is a price to pay elsewhere - meaning a highly-evolved "supermind" is the stuff of science fiction.

University of Warwick psychology researcher Thomas Hills and Ralph Hertwig of the University of Basel looked at a range of studies, including research into the use of drugs like Ritalan which help with attention, studies of people with autism as well as a study of the Ashkenazi Jewish population.

For instance, among individuals with enhanced cognitive abilities- such as savants, people with photographic memories, and even genetically segregated populations of individuals with above average IQ, these individuals often suffer from related disorders, such as autism, debilitating synaesthesia and neural disorders linked with enhanced brain growth.

Similarly, drugs like Ritalan only help people with lower attention spans whereas people who don't have trouble focusing can actually perform worse when they take attention-enhancing drugs.

Dr Hills said: "These kinds of studies suggest there is an upper limit to how much people can or should improve their mental functions like attention, memory or intelligence.

"Take a complex task like driving, where the mind needs to be dynamically focused, attending to the right things such as the road ahead and other road users - which are changing all the time.

"If you enhance your ability to focus too much, and end up over-focusing on specific details, like the driver trying to hide in your blind spot, then you may fail to see another driver suddenly veering into your lane from the other direction.

"Or if you drink coffee to make yourself more alert, the trade-off is that it is likely to increase your anxiety levels and lose your fine motor control. There are always trade-offs.

"In other words, there is a 'sweet spot' in terms of enhancing our mental abilities - if you go beyond that spot - just like in the fairy-tales - you have to pay the price."

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The research, entitled 'Why Aren't We Smarter Already: Evolutionary Trade-Offs and Cognitive Enhancements,' is published in Current Directions in Psychological Science, a journal of the Association for Psychological Science.

Notes to editors

Thomas Hills can be contacted on 44-2476-575527 or t.t.hills@warwick.ac.uk.

Or you can contact Anna Blackaby, University of Warwick press officer, on 44-2476-575910 or 44-7785-433155 or a.blackaby@warwick.ac.uk

The DOI for this paper is 10.1177/0963721411418300