Your Brilliant Baby in Week 14: Understanding Cause and Effect

Reviewed by Dr. Mary Ann LoFrumento in May 2010

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By Baby's fourteenth week, she is beginning to understand cause and effect—that is, that kicking her mobile or yelping for Mommy makes things happen. Baby is learning what she can do—find out more!

Baby's Brain in Week 14

By now, Baby may have graduated to short periods of contentment without you, giving you time to answer an email or fold a load of laundry while she coos in her crib. Sometime soon, take a moment to observe your baby from across the room. You might notice that she can kick her legs in order to whap! the mobile overhead. This action is the first sign of Baby learning cause and effect: "I can move my body to make the mobile dance. This is exciting!"

What the Research Shows

Researchers put three-month-old babies on their backs in their cribs at home and counted the number of times in three minutes that the infants naturally kicked their legs. Then the researchers loosely tied one end of a ribbon to the babies' ankles and the other to a mobile hanging overhead. Much to their delight, the babies realized their kicks caused the mobile overhead to wiggle.

In fact, it pleased these babies so much to see the mobile move that they quickly doubled or tripled their number of kicks to really get the toys overhead to dance. Not only did they enjoy seeing the mobile jiggle, but it was likely amazing for the babies to realize that they could control their environment in this fashion; that their physical skills—kicking—would bring about the object's movement.

Then the researchers removed the mobile from the babies' cribs. Twenty-four hours later, they returned, again tying one end of the ribbon to the each baby's foot and the other end to the mobile. The scientists wanted to know if the babies would need to relearn that their kicking would cause the mobile to move or whether they would start right out flailing their legs as they had the day before, remembering that their own kicks caused the action.

As it turned out, once the babies saw the mobile the following day, they immediately kicked at the more rapid speed, not needing any time at all to re-learn that their leg thrusts caused the mobile's moving. This proved to researchers that at around three months, babies are aware that some of their actions bring about predictable responses in the world around them.