Why do toddlers play next to each other rather than together?

That is parallel play, and it is a normal, expected stage rather than a failure to socialise.

Child development research describes a rough progression: solitary play in infancy, onlooker play where a child watches others, parallel play from around two, associative play where children interact but pursue separate goals, and finally cooperative play with shared aims and roles, which typically becomes reliable around four or five.

In parallel play, children sit near one another using similar materials, largely absorbed in their own activity. They are aware of each other and often imitate — one starts stacking and the other does too — but they are not coordinating.

Why they cannot yet play together properly:

Theory of mind is still developing. Genuine cooperative play requires understanding that the other child has their own intentions and plan. That capacity emerges gradually across the preschool years.

Negotiation requires language they do not have. Agreeing roles, proposing rules and resolving disputes are linguistically demanding.

Sharing requires impulse control that is not yet in place. A toddler taking a toy is not being unkind; they wanted it and the inhibition circuitry is immature.

Parallel play is doing real work. Children in it are observing, imitating, learning turn-taking by watching, and getting comfortable with proximity. It is the groundwork for cooperative play, not a substitute for it.

What helps: provide duplicates of popular toys to reduce conflict, stay nearby to narrate what the other child is doing, and resist pushing them to share before they are able. Adult-mediated turn-taking with a timer works better than expecting spontaneous generosity.

When to raise it: if a child past four consistently shows no interest in other children, avoids eye contact, or does not engage in pretend play, mention it to a health visitor or GP.