Crash, bang, crack. Toddler Stevie begins to explore the wonderful world of breakable objects. How can his parents effectively teach him restraint, yet satisfy his need to explore?

Not by relying on physical punishment say psychologist Thomas G. Power and graduate student M. Lynn Chapieski. They observed sixteen 14-month-old babies (eight boys, eight girls) at play with their mothers, noting every object the babies grasped and their mothers' attempts to restrain them. They also interviewed each mother to find out her usual disciplinary approach: reliance on physical discipline (such as a light slap on the hand), and occasional or conditional physical discipline (such as a light hand slap only after attempts at distracting the child fail) or no physical discipline.

What did they discover? In both the long and short term, physical punishment proved unsuccessful. Babies who were physically punished by their mothers were more likely to grasp breakable objects and were least likely to obey restrictions, reaching for forbidden objects again and again. And when given a test measuring infant development seven months later, these babies scored lower than did those who received no or low discipline. This was especially true of tasks related to spatial skills and problem solving, such as fitting puzzle pieces together and fixing pegs in a board.

Interestingly, mothers who relied on physical punishment made fewer objects available for exploration and play--including safe or unbreakable objects and toys. Power and Chapieski see a connection between this and babies' low test scores later. "In a home where there are very few objects for the baby to play with, you get kids who hesitate to touch objects in the environment," Power says. "This leads to less exploration and a limited chance to improve their visual/spatial skills and problem solving ability."

Thomas G. Power and M. Lynn Chapieski are at the University of Houston. Their study appeared in Developmental Psychology (Vol 22, No. 2).