This study found that meditation can improve concentration and learning. And the mind can show these changes after only 4 days of meditation.

ScienceDaily (2010-04-19) — Psychologists studying the effects of a meditation technique known as “mindfulness” found that meditation-trained participants showed a significant improvement in their critical cognitive skills — and performed significantly better in cognitive tests than a control group — after only four days of training for only 20 minutes each day. The results resembled previously studied cognitive improvements connected to far more extensive training in meditation.

Read more about this study at Science Daily.