You'll be glued to the monitor when your 18-month-old starts chatting himself to sleep. Don't expect to make sense of what he's saying, but it's a great way for him to settle down and process the events of the day, much as you might. “This is a time when older babies may review the day in their own language,” explains Tovah Klein Ph.D., director of the Center for Toddler Development at Barnard College. “They may name things such as ‘dog’ or ‘mommy’ or practice random words they have recently acquired, like ‘bye-bye.’” Such talk is not only enriching, it's relaxing, says Klein. “They are calming themselves into a sleep state,” she says. “Sometimes the speech is repetitive in a soothing way.” Don't feel the need to interrupt; it's just a sign your little one is working through his emotions in an effort to learn how to manage them. There's not much you need to do (except to record it so you'll never forget!), just know it's good for your baby's language, memory and emotional development, plus it's totally normal!