How does a baby develop at 4 month

We have reached the four-month mark. Your little one may already have doubled their birth weight, and from here their weight gain will slow. No wonder, as they are constantly on the move.
What drives all that movement? Curiosity, interest and attention, plus those happy accidents when a move works and they realise it. These bring real joy. All day long they roam, try things, learn and get steadier. This is why giving them plenty of space matters, because room to move helps and so do the new sights and sounds they can take in around the home.

Faces are becoming familiar

From around four months babies gradually start to tell facial outlines and features apart. Visual acuity is at roughly 30 percent. It is an important stage, as depth perception forms with the two eyes and brain working together. This is a process, and since about three months the eyes have been able to move in parallel.

Why are eye checks important?

It is easy to forget how crucial image sharpness is at this age. If, due to a problem, the picture from one eye is blurred, the brain may stop using that eye’s input. If this continues, that eye may never send a sharp picture later on, even with glasses. This is amblyopia. The risk window usually runs to about age five to seven, so screening matters, because issues are easier to spot and treat early.

What about screens?

If the TV is on and your baby can see it, the moving picture is a powerful visual lure. They will not look away. But this makes them focus on a small area with fast motion. They need to practise slow near-far shifts and smooth eye movements. To support healthy visual development, avoid TV viewing. Ideally there is no set in the room where your baby sleeps, as hearing it without seeing it can be unsettling too.

Hearing develops rapidly through experience 

Your baby is going through qualitative hearing development. With constant sound input they begin to tell sources and familiar tones apart and notice what is new. They recognise their parents’ speech and turn towards voices.

Sing to them. Lullabies soothe and they will weave the tunes into their own early “speech”. Talk to them during the day, as it fuels communication, gives feedback and encourages them to search for sound sources. Mum’s and Dad’s voices cannot be replaced by recordings, so your own singing beats a track every time, even if you do not rate your vocals.

When might hearing be a concern?

If crying does not vary, if cooing has not started, or if it is present but stays the same with no new tunes or patterns.

How movement develops at four months 

The bent-limb posture gradually eases. Legs can be drawn up with a slight bend and turned outwards. This is how they learn they can change position. First comes rolling from back to side, often with a head-led push. Arms move symmetrically. Hands meet at the midline and go to the mouth. Limb movements grow more co-ordinated.

If your baby has had regular tummy time, they probably enjoy it by now. With head lifted they hold themselves steadily, and by month’s end that wide arm support narrows to shoulder width.

Free floor space is essential 

Give your baby a generous area and avoid keeping them in the same little spot. We often restrict space out of worry. Yet it is attention and interest that kick off motor progress. Let them explore the flat and you will see movement become steadier and quicker.

Allow free movement and step in only if you spot a safety risk or they signal they need help. If a move is a bit tricky, let them work it out and enjoy the success.

Intentional gestures boost communication 

Your baby is now acting deliberately in many ways. They start to reach out to parents on purpose. They constantly signal with sounds, cooing that is ever more varied and tuneful.
It helps if we always respond. That response can be words, baby-directed speech, a smile, a stroke, picking them up or feeding when hunger cries appear. Every behaviour is communication, even ignoring, which is unhelpful for the baby.

Your baby can form a true two-person relationship 

At first both sides, baby and parent, act intentionally to create and maintain the bond. They turn to each other more. However compelling toys and new movement may be, keeping contact with parents remains vital.
Strengthen that face to face connection with play, gentle rocking, singing, tickles and smiles.

Thinking and learning at four months 

It is a magical phase when babies discover they can affect their surroundings. They draw attention with their voice and make noise with objects.

What is “peekaboo”?

It helps babies grasp object permanence, the idea that things and people still exist when they cannot see them. Hide and reveal toys, cover your face or duck behind something. Soon they will gleefully hide behind the curtain and pop out grinning.

They begin to understand cause and effect more deeply. They use objects in specific ways. They shake a rattle and nudge a roly-poly toy. There is no need to drill or over-direct. Their intrinsic motivation powers exploration. Let them choose which object to reach for and what to grasp.

Link sound with movement. Sing while you sway. These shared-attention moments let your baby attend to speech and motion together.

Every child’s path is individual. Some are motor focused, others tune into communication. Be patient, and if key milestones are missed, seek professional advice.

You may also like our earlier overview of baby development month by month, from birth to 18 months.

References:

Healthier Together (NHS, West London) – Communication & talking skills.

Centers for Disease Control and Prevention (CDC). Developmental Milestones: 4 months