When Tetris effect occurs, your cerebral cortex (the big brain) grows, which was confirmed by 2009 study at Harvard Medical School. The learning activity improves both your intelligence and memory while automating the activity and creating shortcuts to use less mental power for the same task.
You develop dexterity, and the same task comes to you easier and takes less time. The study from 2009 suggests that as much as 90 minutes of practice a week for three months is enough for the brain growth to occur. However, to reap the benefits of the Tetris Effect, the practice should be done in a specific way, which you will discover and try yourself in the next lesson.