One of my very favorite quotes: "Neuroscience tells us that play is critical in helping the brain to work and learn. It’s not the play activity itself that causes learning, though. It’s the repetition that play encourages. Repetitive activity results in patterned neural activity that changes the brain. And the critical link between play and learning -- the reason we keep repeating something and therefore learn from it -- is pleasure.
What constitutes ‘play’ to someone changes over time. Peekaboo excites a baby and stacking and dumping interests a toddler, while a preschooler might prefer extended fantasy play, dressing up like a ballerina or Spider-Man. For a mother or father ‘play’ may be a rousing game of tennis or curling up with a book. But the biology of play always stays the same. When something feels good, the accompanying chemical response makes our brain cells want to experience those positive feelings again. (Or as a toddler is fond of saying, ‘Do it again! Do it again!’ ” (Source: Stamm, J., & Spencer, P. (2007). Bright from the start: the simple, science-backed way to nurture your child's developing mind, from birth to age 3. New York, N.Y.: Gotham Books. Chapter 4. )