When kids first start to play, say around one to two years old, if they are playing “with” another child they are really not playing together so much as playing next to each other. They may watch what each other does, and they may imitate, but they don’t mingle their play. Psychologists call this “parallel play.”
When kids get a little older, provided they are secure and wired up for it, they start to play with each other. Your kid’s doll or truck starts to interact with the other kid’s toy. Voila: the birth of cooperative play.
In this three to five time of life, kids start to build cooperative play in their imaginations. The toys may be props, but the play’s the thing. Group play emerges. Kids playing house, or dinosaurs, or doctor are creating a fragile world that hovers between them—just like grown-ups on a stage or doing improvisational comedy: it is a world of “yes and.”