A central development of the 18- to 36-month period is a child's evolving ability to play with other children and to build friendships. The traditional pattern for this evolution starts before age two with what is called "imitative play," in which one or more children copy the actions of another. Children also play independently side-by-side in what is called "parallel play." The next step, generally by age three, is genuine interaction, albeit not entirely harmonious. There can be bickering over who plays with what toy, and sharing does not come naturally at first. (Parents teaching a child social skills by example is invaluable here.)
However, the path and speed of this evolutionary process of teaching a child social skills is not set in stone and, in fact, is easily altered by group child care. In group settings, children under two can and do play together, and learn child social skills such as turn-taking, sharing, and an element of cooperation. These come about as cognitive development grows and leads children to understand order and sequence. For example, a child may push a nearby object toward another child who is reaching for it. Researchers say this reflects a natural desire for completion of a natural sequence of expected events, rather than empathy or an emotional response to the desire or need of the other child. Yet this desire for completion lays the foundation for later empathy and emotion-based child social skills.
Here's an example of how this might be expressed. Sam, age 25 months, sat contentedly in the middle of the den surrounded by the contents of a spilled bucket of plastic fruit. As he hummed distractedly, he busily matched the fruit according to his own internal sense of classification — sometimes size, sometimes color, sometimes texture. His cousin Alice, 21 months old, sat about six feet away, tearing up a magazine slowly and deliberately, half page by half page. The sound seemed as interesting to her as the tactile sensation of tearing, not to mention the sheer joy in the act of destruction. When she completed her task and sat back to survey the glorious mess, Sam then pushed another magazine to within her grasp without saying anything, as if he knew she was hungry for more. He returned to his sorting without a single social reference to his cousin's play, as Alice set to work again.