Often, though, a toddler's punches pack powerful emotions. "Think of a 1-year-old's world," Dr. Schenck says. "Each day, he's struggling to master new skills and encountering unfamiliar situations." Hitting is a way for a child to express frustration or feelings of being overwhelmed.
"When a 4-year-old has a toy snatched away, he can say, 'That's not fair,' " Dr. Schenck adds. "But a 1-year-old's expressive language skills aren't fully developed."
Toddlers may not realize that hitting can hurt, because a sense of compassion isn't completely in place until about age 3. Even if your child grasps the idea, she may not be able to restrain herself -- 1-year-olds have almost no impulse control. (In fact, this trait isn't usually well-established until about age 5.)