Playing your unborn child Mozart will increase its intelligence. So might feeding it fish oil. Physical exercise, nicotine, coffee, Nintendo's Dr Kawashima's Brain Training, meditation… all have been heralded as pathways to making us smarter.

Some of these, as US journalist Dan Hurley explores in this intriguing book about "training" intelligence, are plain nonsense: academia quickly proved there was no Mozart Effect (learning a new instrument is more likely to have benefits), fish oil may even have a negative impact on later cognitive abilities and Nintendo itself said Dr Kawashima was purely for entertainment. Hurley does a fine job of wading through the research and also embarks on an enjoyable project to try and increase his own "fluid" intelligence – the underlying ability to learn which usually peaks in early adulthood. He begins seven programmes which he thinks have proven successful – including an exercise boot camp and learning the lute – and tests himself at the beginning and end of the process. First on the list is the computer game many cite as kickstarting the new science of intelligence training: N-Back.

It would take this whole review to explain how N-Back works (just play it online) but its creators Martin Buschkuehl and Susanne Jaeggi published a study in 2008, that found the test didn't just improve working memory but fluid intelligence – by more than 40% in some cases. Tellingly, the US military were quickly involved in funding N-Back. But many aren't so sure and the shame of this book is that after piquing our interest and beginning his training, Hurley gets bogged down in academic debate. It's only in the very last pages that we go back to his experiences – and the results are mixed. He resorts to having to say he "feels smarter". But then, this isn't a headline-grabbing manual, it's an investigation into the industry growing up around this new science. Makes you think.