Given that we've been evolving for millions of years, and generally reckon it's our intelligence that's given us the edge as a species, it's perhaps surprising that we're all not a little bit brighter.
But according to researchers at the University of Warwick and the University of Basel, we've pretty much hit the limits, and we're never going to develop a science fiction-style 'supermind'.
Thomas Hills and Ralph Hertwig looked at a range of studies, including research into the use of drugs like Ritalan which help with attention, studies of people with autism and a study of the Ashkenazi Jewish population.
And they've concluded that there's just too severe a penalty. For every gain in cognitive functions, they say - such as a better memory, increased attention or improved intelligence - there's a price to pay elsewhere.
For instance, people with enhanced cognitive abilities - such as savants, people with photographic memories, and even genetically segregated populations of individuals with above average IQ - 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.
"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," says Hills.
"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."