VALLEY SPRINGS - Erin Cottle, 17 months, and Deven Anderson, about the same age, got off to a rocky start Monday morning. They met over a puzzle. Something under Deven's control, possibly a piece of the puzzle, smacked Erin's eye.

Tears flowed. Erin retreated to her mommy, Catriona Cottle, for a kiss, a hug. Deven, concerned, toddled over to see if she was all right. The storm passed. First Deven, then Erin, slipped happily back to playing with 15 other children on the carpeted floor of a rented martial arts studio.

Such bumps and adventures were once a routine part of childhood. These days, however, unstructured play with other youngsters is limited or absent for many children, pushed aside by the isolation of a car-oriented society, busy schedules and even electronic entertainment, say parents and early childhood development experts.