Cohen Kadosh added that it was important to identify any downsides of this and other similar forms of transcranial electrical stimulation to ensure that boosting one cognitive ability did not lead to damage in another.

BBC: Brain stimulation promises 'long-lasting' maths boost

They used a technique called transcranial direct current stimulation, or tDCS. If you pass a weak electrical current through part of the brain, it temporarily and safely disrupts neural activity.

WSJ: Mind & Matter: Alison Gopnik on Beating the Brain's Curbs on Innovation