Who needs to write it down? (Image: Jeffrey Coolidge/Getty)

Are you bad at sums? Never remember your times tables? Now you can simply zap your brain with a pulse of electricity to make mental arithmetic a whole lot easier.

In 2010, Roi Cohen Kadosh at the University of Oxford and colleagues showed that a technique called transcranial direct current stimulation could help people to learn and process symbols representing numbers.

Now, his team has shown that a similar procedure can help people improve their mental arithmetic – and crucially, the effects are long lasting.


This non-invasive procedure could help children with learning difficulties, or be used in the rehabilitation of people after a stroke. It might even be able to help other people improve their mental athleticism.

Random noise

Cohen Kadosh’s team used transcranial random noise stimulation (TRNS), in which electrodes placed on the surface of the scalp deliver a fluctuating electrical signal to specific regions of the brain, exciting the neurons. In this case, the electrodes were placed over volunteers’ prefrontal cortex – an area of the brain involved in performing mental arithmetic.

The team gave one group of 25 people TRNS and gave a second group of 26 sham treatment – they wore the electrodes but no current was passed through. Both groups were initially equally fast at their sums.

After just five consecutive sessions, each lasting about 40 minutes, the people given TRNS significantly improved their ability to do mental arithmetic. They were twice as fast at doing the actual calculations and their rate of improvement was twice that of the other group. Their “drill learning”, the ability to recall arithmetic facts such as multiplication tables, also improved five-fold in both measures.

To find out what was going on, the team measured the flow of oxygen in the brain during the tasks. They did this using near infrared spectroscopy, which involves shining a non-invasive infrared light into the brain and measuring changes in the absorption of the light. These changes correspond to changes in oxygen concentration in the brain.

They found that TRNS seems to increase the efficiency with which stimulated brain areas use their supplies of oxygen and nutrients.

After six months, half of the participants were tested again. The TRNS group could still perform the mental calculations 28 per cent faster than the sham group.

What’s the cost?

Earlier this year, Cohen Kadosh published work showing that although some brain stimulation can improve cognition, this comes at a cost to other cognitive functions. In the new study, his group tested for unintended consequences on several non-mathematical tasks but found no effect – positive or negative.

That’s not to say that there aren’t any downfalls to a quick mathematical boost, says Cohen Kadosh, but larger studies would be needed to investigate this in more detail.

The technique could potentially help rehabilitate people with stroke, or help children learn. “We aim to start a study with children with numerical learning difficulties,” says Cohen Kadosh, “and we plan to extend it to other populations.”

Journal reference: Current Biology, DOI: 10.1016/j.cub.2013.04.045