Parallel play (or parallel activity) is a term that was introduced by Mildred Parten in 1932 to refer to a developmental stage of social activity in which children play with toys like those the children around them are using but are absorbed in their own activity and usually play beside rather than with one another. Children in this stage may comment on what they are doing or imitate what another child does, but they rarely cooperate in a task or engage in dramatic play or formal games with others. This stage occurs after solitary and onlooker play and before associated and cooperative play when children engage in more complex social interactions. Preschool children of all ages engage in parallel play, particularly when using sand, water, blocks, and art materials; this type of play appears to serve as a bridge to more complex cooperative activities.
Bakeman, R., and J. R. Brownlee. "The Strategic Use of Parallel Play: A Sequential Analysis." Child Development 51 (1980):873-878.
Parten, Mildred B. "Social Participation among Preschool Children." Journal of Abnormal and Social Psychology 27 (1932):243-269.
Rubin, K. H., William Bukowski, and J. G. Parker. "Peer Interactions, Relationships, and Groups." In William Damon and Nancy Eisenberg eds., Handbook of Child Psychology, Vol. 3: Social, Emotional, and Personality Development. New York: John Wiley, 1998.