Baby talk can be cute when you baby is first figuring out how to sound out words -- but not so much in an older child. It can be downright grating and annoying but many kids use it far beyond the baby years for a variety of reasons. Often it's less a regression than an indication of emotional advancement; they have chosen to use something specific to their advantage.
When a child who is more than capable of age-appropriate communication begins to talk intentionally like a baby again, she clearly is trying to draw attention to herself. Baby talk -- for kids as well as adults -- is associated with cuteness and positive attention, and the child has made that connection: If I talk like a baby, I'll get the kind of positive attention I want.
Is it really a regression?
If your child is choosing to talk like a baby, probably not. If your child is suddenly unable to speak and communicate in the way he was able to before, then that is a true regression, and likely requires some input from a medical care provider to figure out what is going on. Early intervention for any regression increases (but does not guarantee) a chance at returning to the forward developmental path. Bring any concerns up to your child's pediatrician and other medical care providers.
Changes and anxieties
Sometimes, a child who decides to use baby talk is experiencing some change or stress that makes him crave the kind of attention a baby gets. Kids experience stress just as grownups do. How they manifest it, though, can vary significantly among children. While some kids act out and get angry, some take steps to "go back" to a time they perceive as safer and easier.
Ironically, one way you can sort the issue out is through more grownup-style communication. Talk to your child directly about issues and changes that may be bothering her -- they might not be obvious! -- and offer lots of reassurance that you'll be there to help her along. In addition, let your child know that, although baby talk was cute when she was baby, it's not so cute now, and one great thing about getting a little older is her ability to communicate better.
Even though the baby talk may be annoying, putting a positive spin on age-appropriate speech and communication may get you further than snap reactions.
More on kids' developmental milestones
Your 3-year-old: Development, behavior and parenting tipsYour 4-year-old: Development, behavior and parenting tips3-year speech delay: When should you see a specialist?