People have always sought advantages over their rivals. But trying to improve intelligence as a way to do it has been off-limits. An education can be bought, but ability? You either had it or you didn’t. Now a new science called cognitive enhancement promises that someone who doesn’t have intelligence today could have it tomorrow.

Using science to boost intelligence might sound far-fetched, but some people in high places take the prospect very seriously indeed. In the dying days of Tony Blair’s premiership, British government officials asked an expert panel to look at the possible political impact. Britain wanted to know if other countries – economic rivals – might be willing to introduce national programmes to artificially boost the intellectual “quality” of their populations.

State-funded scientists in China have run experiments to see if pressurised oxygen chambers – the type typically used to treat scuba divers with the bends – can improve mental performance. Without waiting for the results, ambitious families are booking their teenagers into these chambers the night before the pivotal Gaokao school-leaving test, the traditional route to higher education and a secure career with the state.

Closer to home, the use of smart drugs is common. Some surveys suggest that as many as a quarter of UK undergraduates have taken modafinil or a similar medicine to help their work. A fifth of surgeons say they have taken it, and a similar number of professional scientists. In Britain, it’s a prescription-only drug, so it’s legal to possess but illegal to sell and supply.

Several startup neuroscience companies already sell basic electrical brain stimulators online that they claim will supercharge neural activity. These efforts piggyback on parallel efforts in universities and hospitals that aim to use cognitive enhancement to address the gathering dementia crisis of an ageing population, and the lack of reliable treatments for mental disorders that burden at least a quarter of the global population. The question is only how far this cognitive enhancement research will spread its influence into broader society. There is a strong tradition, after all, of medical treatments being borrowed by the healthy to enhance normal performance: drugs in sport is the most obvious example.

Is brain doping fair? Should it be allowed, or even encouraged? Could it increase our attention? Our memory? Our maths and language skills? And if it can, what are the implications for society? It’s too soon to answer all of these questions, but it’s not too soon to ask them. I believe cognitive enhancement works because I used it to help increase my own intelligence. The evidence? I used it to cheat my way into Mensa.

The international high-IQ society, Mensa offers membership to people with IQ in the top 2% of the population. On the most commonly used scale, that’s an IQ of 130. There are well over a million people in the UK with an IQ of 130 or above. The membership of Mensa UK is about 21,000 people. So clearly, not everybody with a high IQ wants to join a high-IQ society. That made the dozen or so people I met at a London university one Saturday morning in 2015 something of a rarity. They were there to join. I was there to get my baseline IQ score before I started a self-experiment in cognitive enhancement.

There were two separate tests. The first was symbols and shapes: the odd one out; next in a series; what it looks like if you rotate in this direction. Then a second paper swapped the symbols for words. The format was the same but the focus this time was language.

It took a couple of weeks for my results to drop through our letterbox. The word Mensa was clearly visible through the envelope, so it took a couple of seconds for my wife to “open it by mistake”. She called me at work with the news.

“Ha, you got in. I knew you would,” she said. I told a colleague, and in doing so realised there is no way to tell people you have got into Mensa without coming across as smug and a bit odd. How do you know if someone you meet at a party is in Mensa? They will tell you.

I took a closer look at my Mensa test results. I hadn’t passed the first test at all. But I didn’t need to. To join Mensa, applicants need pass only one of the two separate papers. And my score on the second, the language, was high enough. But, working as a journalist, I thought I had a natural advantage when it came to language.

The first test felt much more like a true measure of natural brain power, so that became my goal: to improve my score and pass that test with the help of cognitive enhancement. But I was going to have to wait. Taking an IQ test for a second time comes with a built-in improvement. It’s hard to be sure how big this retest effect is, or how quickly it wears off. To be safe, I decided to wait a year, which is how long Mensa asks people who fail to get in to wait until they try again.

My goal of increasing intelligence – cognitive enhancement – is a tricky thing to identify. Is it enough to achieve an increase in IQ score?

Critics of IQ tests, and there are many, like to point out that it’s ridiculous to try to reduce the myriad abilities and potential of a person to a single representative number. They are right, but it is not clear who they are really arguing with. It is much harder to find someone – at least someone who fully understands IQ tests – who truly believes they should be used that way.

IQ is not so much intended as a measure of individual ability, but a way to compare differences in that ability. And, on average, better performance on IQ tests does indicate higher levels of achievement in the wider world.

First, and most unsurprising given the pen-and-paper style of most IQ tests, students with higher scores tend to spend more time in education and achieve better grades. Are these people only book-smart, and not street-smart? It seems not – the same positive association shows up in the workplace. The employees who are judged the best performers and managers by their bosses and colleagues are most likely to be those with higher IQs. This applies to all sectors, from white-collar, highly skilled professional work to low-complexity, blue-collar jobs.

Performance and pay are linked, and sure enough, those with a high IQ tend to earn more money. And they are less likely to suffer from high blood pressure and heart disease, less likely to be obese, and less likely to have a psychiatric disorder needing hospital treatment. They will probably live longer. Some studies suggest a relatively low IQ carries the same extra risk of an early death as smoking.

A year on, by the time of the Mensa retest, I had bought online a basic brain stimulator: two electrodes wired to a 9V battery (one of the chunky ones from a smoke alarm) that I connected to wet sponges pressed to my scalp. For 30 minutes each night for a week before the test I aimed the current at my anterior temporal lobes, above my ears, trying to copy an experiment in Australia that seemed to show an improvement in volunteers asked to solve puzzles.

Electricity has been applied to the brain to try to change just about every cognitive function, with some success. Before it deployed soldiers to Iraq in the early 00s, the US army made them play a video game to simulate what they would encounter. Volunteers who had a 2mA current applied to the right side of their skull, above their inferior frontal cortex (behind the temple) or right parietal cortex (beneath the crown on the right-hand side), improved twice as fast as the others when it came to identifying threats. (Although one dropped out because they said they experienced a burning pain.) The effect lasted for at least an hour after the current was switched off, which suggests the stimulation might have provoked lasting change in the brains of the volunteers.

These sort of experiments have inspired DIY communities who like to be known as “brain hackers”. Largely outside bona fide research institutes and universities and beyond the reach of any regulation or control, these people are building brain-altering equipment and using it on themselves. They swap stories, techniques and tips over specialist sites on the internet. They film their experiences and upload them to YouTube.

My brain self-stimulation started with a bang. As I turned the switch from off to 2mA, a flash of light shot across my vision, a tracer bullet passed through my brain. I gasped, and my wife – already nervous about my self-experimentation – leaned forward ready to pull the plug on it. It was a phosphene, a pinprick of light not there and created only by the electrical stimulation of the retinas at the back of my eyes, or more likely my brain’s visual cortex. Phosphenes are harmless, but they do show that messing with the brain can have unexpected consequences. At the moment, there is no evidence of harmful side-effects, but electrical brain stimulation can certainly go wrong. Some home users have said they burned themselves quite badly.

On the morning of the Mensa retest, I also took a smart pill: some modafinil that I had bought online and a friendly chemist had tested to make sure it was genuine.

The effects of smart drugs are often hyped and exaggerated. But solid evidence suggests modafinil has a positive and significant effect on cognition. It’s been shown to improve the performance of healthy volunteers in several tasks – recalling a series of numbers, decision making, problem-solving and spatial planning among them. In August 2015, scientists at Harvard and Oxford universities pooled and analysed all of the most reliable experiments and concluded that modafinil is the world’s first safe and effective smart drug.

By safe, they mean in the short term. Nobody knows what the long-term effects might be, partly because scientists haven’t tracked chronic modafinil use, and partly because they are not sure how the drug works, or indeed what it does in the human brain.

I felt the drug made me more alert and helped me to concentrate. I whizzed through the early easy questions, but as time ticked on and the puzzles got trickier, a curious thing happened. The modafinil – at least I think it was the modafinil – dragged me fully into each question, and made it more difficult to take an educated guess and move on. Where I could see the answer early on, the drug acted as an accelerator. But when some effort was required, it was almost a brake. I was sucked into the problem, the way it was phrased and posed, and, if I was taking too long, I found it harder to walk away from the intellectual challenge and move on to the next question. (In January 2017, scientists in Germany reported what looks like a similar effect of modafinil on expert chess players. Those given the drug made better moves, but actually lost more games on time penalties.)

When Mensa sent me the new results, my IQ as measured by the symbols test was now 135, up from 125 a year before, and so well above the threshold required for Mensa membership.

Was the increase down to my efforts at cognitive enhancement? It is impossible to know for sure, but I think some of it was. Still, it is hard to disentangle all of the confounding factors, which is why science and medicine do not take one-off results in such uncontrolled trials seriously as hard evidence. Even if the effect is genuine, we can’t tell if one of the methods I tried worked better than the other. I am only a case study. But case studies can still be useful. They can identify effects that require attention, exploration and, eventually, explanation.

The rise of cognitive enhancement challenges us to think about intelligence and ability in a new way. Around the time the UK government asked experts to investigate enhancement, the Parliamentary Office of Science and Technology produced a briefing note on the topic for British policy makers. “Widespread use of enhancers would raise interesting questions for society,” it said. “Currently, individuals with above-average cognitive performance in areas such as memory and reasoning are valued and rewarded. Making such performance readily available to all individuals could reduce the diversity of cognitive abilities in the population, and change ideas of what is perceived as normal.”

Just as with doping in sports, the benefits that cognitive enhancement techniques offer do not have to be colossal to be significant. Intelligence is relative. It’s like speed in the old joke about the two wildlife cameramen filming a lion. As the hungry beast notices them and gets roaring to its feet, one of the pair slips off his jungle boots and laces up a pair of trainers.

“You’ll never outrun a lion,” says his colleague.

“I don’t need to. I just need to outrun you.”

To investigate, to explore and explain, the only way is to pay attention and to carry out larger and more controlled trials. Should we? I think we should, if for no other reason than to give society the evidence it needs to decide what to do about cognitive enhancement. It seems the smart thing to do.

The Genius Within by David Adam is published by Picador on Thursday (£16.99). To order a copy for £14.44, go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99