When a child plays on their own they are in complete control of their activity. They decide what their play involves, how their play develops and when to stop. This level of control gives the child the engagement that makes play so powerful. The control comes from allowing certain things to happen and preventing other things from not happening. For example, when playing with construction toys, a child decides which pieces to use to represent whatever it is they are building. This could be defined by the pieces themselves (maybe some of the pieces are specifically designed represent certain things, such as windows or trees) or the child defines what the piece is (they might use a block to represent a door). The child is free to stop building whenever they want to.
When children play together, the activity develops in a similar way. All the children must decide together how the activity progresses and it does so by children allowing the ideas of others to shape the play. There is potential for one child to be the 'leader' but this only happens with consensus from all of the children involved because without agreement, the play will fall apart. If the child feels the activity is no longer what they want to do, if they feel they can no longer accept the 'rules' then they are free to leave the game.
So what about adults? It's certainly possible for adults to play with children but because they are usually seen as being 'in charge' a child may feel that they are unable to leave the activity. This can easily mean that there is no play happening any more! This is where adults need to be very careful with their interactions when interrupting or initiating play. Practitioners need to know their children and the children need to trust the adults. That way adults can make the right decision with play:
But how do you choose which to do when? It is generally accepted that deeper learning takes place when children are most interested and engaged with their activity. The greatest levels of interest and engagement will take place when children are freely allowed to choose their play. So where possible we want children to feel that they are in control. We may adjust the environment to give different learning opportunities or we may integrate ourselves into the play but we should keep in mind that if we want the children to be playing then we need to allow them control.
After all, if there's one thing us adults are good at - it's not being in complete control, right?!