Your Brilliant Baby in Week 20: Understanding Trajectory


Cars, toys, balls, people: Right now Baby is keenly aware of the way items around her move through her world. Learn more about your child in week 20.

Baby’s Brain in Week 20

Note how intently Baby tracks the dog darting across the lawn in front of her, or the way the vacuum passes along the carpet and around furniture. At about five months, your child is enraptured by the way objects move across the floor and ground. But why?

As you know, infants’ lives are all about survival—and they’ll likely survive with more ease if they can predict how objects move and whether that movement may affect them. Once babies make these predictions (and those guesses are verified after much trial and error), they become more comfortable with happenings in the world around them—and they’re free to satisfy their curiosity about other matters in the home environment.

What the Research Shows

From the following study, researchers know that five-month-old babies are highly interested in trajectory, the path a moving object follows through space. Five-month-olds were placed in front of a screen. They could see a toy car being pushed from one side of the screen, and watched as the car then would travel behind the screen and soon reappear on the other side. The researchers would repeat the car’s path several times.

Then the researchers enacted the same sequence again, except this time they stopped the car from reappearing on the other side of the screen. When they did so, the babies would appear perplexed: “Where did the car go?” They sensed something was wrong, as by now they understood the car’s trajectory and expected it to reappear as always.

Taking the experiment one step further, researchers then pushed a car behind the screen and had a toy duck come out on the other side. The five-month-old babies didn’t care. Even though a completely different item appeared after they saw the car disappear, they didn’t flinch. They were expecting something to reappear but didn’t care what it was. Movement alone was what these five-month-olds were concentrating on and learning about.

Further trials revealed that when babies who are a bit older—12 months—see a car go in and a duck come out, they are perplexed. By one year, babies are able to focus not only on movement but also on what is moving.

Week 20 Brain Booster

Since your baby is learning about movement, set objects in motion around her. With her propped up on the floor so she can see, roll balls around the room. Race toy trucks in front of her and behind her back. At the post office, purchase a tube used for mailing rolled-up papers: Once home, roll balls and other small toys through the tube. This activity will elicit smiles for days, weeks, and possibly months as your child masters the laws of trajectory.


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