1) The document discusses how the brain is like a muscle that can grow stronger through exercise and challenges. It compares brain development to physical fitness, stating that challenging your mind leads to more connections between brain cells.
2) Babies learn language by exercising their brains through listening, practicing speech, and having conversations - this causes their brains to physically grow and develop.
3) The document promotes intellectual challenges and problem-solving as ways to strengthen the brain and increase intelligence over time. It claims that an "exercised" brain is more capable of meeting goals and tackling difficulties.