According to the official rankings, Conor Muldoon has the 239th best memory in the world. He would probably be justified in calling himself the Irish number one in the 'mind sport' of competitive memorisation – whose participants contend with each other to remember things – except that this may not be quite as impressive as it sounds. "I know of two other competitors here," he says. "But I've never met them. There isn't a community."

Muldoon, a postdoctoral researcher in the computer science department at UCD, is a mnemonist. Mnemonists, who have been known to describe themselves as 'mental athletes', train their brains to look at long strings of data – numbers, dates, playing cards – and then recall them. There is an annual World Memory Championship, which is in its 18th year; this time around, the overall winner will take home a $10,000 prize.

Over a coffee at the campus cafeteria, Muldoon, a quiet man in his late 20s, tells me what sparked his interest. "A few years ago," he says, "I read a book called Use Your Memory by Tony Buzan. He's one of the main guys who started the whole World Memory Championships. I was doing research for my PhD at the time, so I thought it would be a good thing for that. To keep the brain exercised. Use it or lose it." He thought it might help him remember academic papers, he says. "So I started doing the techniques."

The official disciplines of the World Memory Sports Council are not for the faint-hearted. Competitors are presented with a long string of meaningless information and given a set time to memorise it. The more you can correctly remember afterwards, the higher your score. The feats involved can be (literally) mind-boggling. In the 'One Hour Numbers' discipline, the world record is held by Gunther Karsten, who after 60 minutes recalled to mind 1,949 digits – having spent less than two seconds looking at each.

Last year, Muldoon entered his first competition: the 2008 UK Open. It was, he says, "a bit daunting. You just have a room full of tables, all facing one guy at a table. And they come round with different sheets of numbers, cards, the different disciplines. You do one competition and then there's a break, then you do another event and there's a break."

Muldoon came in 21st out of 22 competitors at the UK Open – but was undaunted. "If you don't sign up for something, then you don't really push yourself," he says. "And it's interesting to meet new people over there, and see what their experiences of memory have been." So this year, he entered the inaugural Welsh Memory Championship.

Dai Griffiths was the organiser of that competition, and is an energetic evangelist for mnemonic methods. How did he get interested in memory? "When I was 11 years old, my grandfather bought a new car and wanted me to remember the number plate," he says. "He knew I was inclined to wander off on days out to Abergavenny and Merthyr Tydfil. So he asked me how I was going to do it."

Dai didn't know. "He told me to imagine the characters from comics I was reading at the time, or people's names that began with each letter. Then he painted the picture in my mind for me. In the driver seat was Walter, behind him was Victor, next to Victor was Johnny and in the passenger seat was Tommy. Then he said it as a rhyme: Walter, Victor, Johnny, double six, nine, Tommy."

Griffiths suggests the information is in there somewhere, but it hasn't been properly organised. "Something has been memorised but, it has not been given a storage space," he says. "So when people need to recall the information, they don't know where in their own brain to look."

Writer and blogger Joshua Foer is halfway to being living proof of this. The brother of novelist Jonathan Safran Foer, he was working as a science journalist in the States when he went to cover the US Memory Championships in 2005 – "thinking it sounded like a curious, strange thing". It ended up sparking his interest. "I met a guy named Ed Cooke, who was one of the top mnemonists in Europe," he says. "He took me under his wing and taught me everything he knew about memory training. One thing led to another, and I ended up competing in the following year's US championships." Against all expectations, including his own, he won.

So what was the experience like? "It was pretty gruelling," he says. "International memory competitions are referred to as a 'mental decathlons'. Sounds ridiculous, I admit, but it's actually an apt description. The competitions fry your brain."

Foer – who is writing a book about his experiences called Moonwalking With Einstein, with a film also in the works – hasn't competed since 2006. But he did represent the US at the World Championships that year. He got "totally clobbered," he says. "Europeans take the 'sport' much more seriously than Americans."

Could mnemonism ever be a professional sport? Griffiths thinks so. "One day memory competitions will be televised live," he says.

He is a firm believer, too, in mnemonism's power to unlock human potential. "I would like to see the sport become a part of the Olympics and on the curriculum in every learning establishment form nursery to university."

It's a tenet among advocates of mnemonism that despite the sport's somewhat Dungeons and Dragons-esque aura, it does have have real-world applications. "I think it does help out in other areas," Muldoon says, and suggests that our memories make up a bigger part of our thinking than we might realise. "Almost any decision that you make, anything you do in life really is just a function of memory. So improving your memory improves all sorts of areas in ways you wouldn't expect. I think the way Tony Buzan would describe it is, the brain is like a muscle, and it's the more you exercise it. Like going to the gym and lifting weights, but for your brain."

Foer is more sceptical. "Your memory is not some single, monolithic thing that can be improved," he says. "Anybody who tells you that your brain is a muscle that can strengthened through this kind of training is a huckster. These are specific techniques with specific uses." But that's not to say they're without their niche. "They do come in handy in my day-to-day life, when I choose to use them. I know that when I need to remember something, I will." And in the end, he agrees, what we remember makes us who we are. "We are nothing more and nothing less," he says, "than our memories."