At four months old, your baby is hitting a sweet spot of development where personality starts showing through. You can expect purposeful smiles, early laughing, better head control, reaching for objects, and the beginnings of babbling. Every baby develops on their own timeline, but here’s what most four-month-olds are working on across the major areas of development.
Movement and Physical Skills
Head control is one of the biggest physical achievements around this age. When you hold your baby upright, their head should stay steady without wobbling. During tummy time, most four-month-olds can push up on their forearms and lift their head and chest off the floor, giving them a better view of the world around them.
Some babies start rolling from tummy to back around this time, though rolling in both directions often comes a bit later. When held in a standing position on your lap, your baby may push down with their legs, bearing some weight. This isn’t walking readiness; it’s just their muscles getting stronger and their brain figuring out how legs work.
Tummy time matters more than ever at this stage. The NIH recommends working up from short three-to-five-minute sessions to a total of 15 to 30 minutes per day by two months, so by four months your baby should be comfortable with longer stretches. These sessions build the neck, shoulder, and core strength that make rolling, sitting, and eventually crawling possible.
Hands and Reaching
Four-month-olds are discovering their hands in a big way. Your baby will likely reach for toys and other interesting objects, sometimes successfully grabbing them. They can hold a rattle or small toy and may shake it, though their grip is still clumsy. Bringing hands (and everything else) to their mouth is constant at this age. This isn’t a sign of teething necessarily. It’s how babies explore texture, shape, and taste.
You may also notice your baby watching their own hands, opening and closing their fingers, or clasping both hands together at the midline of their body. These are all signs that hand-eye coordination is coming online.
Communication and Sounds
This is the age when “conversations” start to feel real. Around four months, babies begin cooing and making vowel-like sounds (“ooh,” “aah”), and they’ll often pause and wait for you to respond before making more noise. It’s a back-and-forth pattern that mirrors actual conversation, and it’s one of the earliest building blocks of language.
Laughing typically appears between four and six months. Your baby may chuckle at peek-a-boo, funny faces, or unexpected sounds. They’re also learning to communicate displeasure more clearly, with different cries for hunger, boredom, and discomfort becoming easier for you to distinguish.
Social and Emotional Development
By four months, social smiling is well established. Your baby has been doing this since around two months, but now those smiles are more frequent and more targeted. They’ll smile at familiar faces, smile in response to your voice, and may even flash a grin at their reflection. Babies at this age also start showing a clear preference for familiar people, getting excited when they see a parent or caregiver.
Facial expressions are getting more varied. Your baby might look surprised, frown, or widen their eyes, and they’re becoming better at reading your expressions too. If you look upset, your baby may respond with a concerned expression. This emotional mirroring is an important part of social development.
Vision and Cognitive Skills
Your baby’s vision has sharpened considerably since birth. At four months, they can track a moving object smoothly with their eyes, following it from side to side. Color vision is maturing, and they’re drawn to brighter, more contrasting colors. They can now see across a room, though they still prefer looking at faces up close.
Cognitively, four-month-olds are starting to understand cause and effect in simple ways. When they bat at a hanging toy and it moves, they’ll do it again on purpose. They recognize familiar objects like their bottle and may get excited when they see it. They’re also beginning to notice when something disappears, though true object permanence (understanding that hidden things still exist) won’t develop for a few more months.
Sleep at Four Months
Most babies this age sleep 12 to 16 total hours per day, split between nighttime sleep and at least two daytime naps. Daytime sleep averages about three to four hours total. Some four-month-olds are sleeping longer stretches at night, but many are not, and both are normal.
You may have heard of the “four-month sleep regression,” and it’s real. Around this age, babies shift from newborn sleep patterns to more adult-like sleep cycles, which means they briefly wake between cycles. A baby who previously slept long stretches may suddenly start waking every few hours. This is a normal neurological shift, not a step backward. Separation anxiety can also start emerging around this time, causing nighttime fussiness when a baby realizes you’re not in the room.
Feeding at Four Months
At four months, breast milk or formula remains your baby’s only nutritional need. Both the AAP and the Dietary Guidelines for Americans recommend waiting until about six months to introduce solid foods. Introducing solids before four months is not recommended at all.
Some pediatricians give the green light for solids between four and six months if a baby shows specific readiness signs: sitting up with support, good head and neck control, opening their mouth when food is offered, swallowing food instead of pushing it out with their tongue, and showing interest in what you’re eating. At four months, most babies haven’t hit all of these markers yet, so there’s no rush.
Signs Worth Mentioning to Your Pediatrician
Babies develop at different speeds, and being a little behind on one milestone isn’t usually a concern. But certain patterns are worth bringing up at your next visit. If your baby doesn’t watch things as they move, doesn’t smile at people, can’t hold their head steady when supported upright, doesn’t coo or make sounds, doesn’t bring things to their mouth, or doesn’t push down with their legs when feet are placed on a hard surface, mention it.
Losing skills your baby previously had is a more urgent signal. A baby who was cooing and stops, or who was tracking objects and no longer does, should be evaluated. Early intervention services are available in every U.S. state, and the earlier a delay is identified, the more effective support tends to be.