Here is a great article from the Luminosity website about Brain Training:

Because the science of neuroplasticity and cognitive enhancement is relatively new, a number of myths surround brain training. These myths, though, are exactly that – myths – which is why we’d like to take a moment to separate fact from fiction.

Cognitive exercise only makes you better at cognitive exercise.

FICTION! Controlled clinical trials show that the right kinds of cognitive exercise can fundamentally enhance the brain’s ability to process the information needed for daily and professional tasks. Studies research performed at Stanford and Berkeley have demonstrated 10-20% improvements in memory, attention, and speed of processing.

Cognitive training can help anyone at any age.

FACT! Everyone can improve! 97% of all users who train for at least 10 hours see improvements in performance. Who couldn’t benefit from enhanced memory and attention?

People don’t need brain training if they do crosswords or similar activities.

FICTION! It is recommended doing a variety of things to keep the brain in top form, including proper diet, physical exercise, adequate sleep, and staying socially active. However, none of these lifestyle factors specifically target the core brain regions that underlie cognitive functions such as attention, memory and speed of processing.