"Brain training" is a multi-million dollar industry. These activities are intensive computerized training exercises designed to improve your cognitive ability — to grow your brain.

In a recent issue of Nature, researchers recruited more than 11,000 participants and divided them into different study groups. These groups had "brain training" several times each week on tasks that were supposed to improve reasoning, memory, planning, eye-hand coordination and attention span. Each participant was tested on basic mental function before and after the six weeks of training.