Somewhere around four months a baby starts making noise at you on purpose. Not crying, not the windy half-sounds of the first weeks. A deliberate ah aimed at your face, then a pause. The pause is the interesting part. They're holding the door open for you.
Researchers call this serve and return. The baby serves, you return, they serve again. It looks like nothing. It's the scaffolding every later conversation gets built on, and babies who get a lot of it hear far more language in a day than babies who are talked at.
What returning actually looks like
- Copy the sound back before you improve on it. They said ba, you say ba, then you say ball. In that order.
- Wait longer than feels natural. A baby needs about five seconds to organise a reply. Most adults wait one.
- Follow their eyes. Whatever they're staring at is the topic they chose. Name that, not the thing you wanted to talk about.
- Answer the pointing. A point is a question. Any answer counts.
You aren't teaching words yet. You're teaching that making a sound causes something to happen.
This is also why narrating your day works so well at this age. Peeling a carrot out loud is dull for you and rich for them: your voice keeps moving, your face keeps changing, and every so often they serve and you get to return. The nappy change, the walk to the car, the long minutes where you both watch the washing machine. All of it counts, which is either reassuring or exhausting depending on the day.
The bit nobody warns you about
Babies look away mid-conversation, and it's easy to read as boredom. It's usually the opposite. Their nervous system tops out faster than yours, so they break eye contact to cool down, then come back. If you chase the gaze, you extend the overload. If you wait, they return on their own, generally within half a minute.
Reading works the same way this year, which surprises people who think books start at two. A board book at eight months isn't a story, it's a shared object with a rhythm and a turning page. They chew the corner, you keep reading, they look up when your voice changes. That's the whole exercise, and it's enough.
