The environment also brings out what security experts call the "mama-bear instinct." A Chuck E. Cheese's can take on some of the dynamics of the animal kingdom, where beasts rush to protect their young when they sense a threat.

Stepping in when a parent perceives that a child is being threatened "is part of protective parenting," says Frank Farley, a psychologist at Temple University and former president of the American Psychological Association. "It is part of the species -- all species, in fact -- in the animal kingdom," he says. "We do it all of the time."