Limiting the Child's Life Space
Placing an unacceptably behaving child in a playpen, is an attempt to limit the child's "life space" so that her subsequent behaviors will be acceptable to the parent. Fenced-in backyards are effective in preventing such behavior as running out into the street, walking through the neighbor's flower garden, getting lost, and so on.
Some parents designate a special area in the house where the child is permitted to play with clay, to paint, to cut up paper, or to glue, limiting such messy activities to that special area. Special areas can also be designated as places for children to be noisy, roughhouse, dig in the mud, and so on.
Children generally accept such limitations of their life space, provided they seem reasonable and leave children considerable freedom to meet their own needs. Sometimes a child will resist the limitation and cause conflict with the parent.
*Excerpt from Dr. Thomas Gordon's P.E.T., Parent Effectiveness Training book