Baby's Brain in Week 29
By now, your baby is entirely aware of your playtime together. She's knows that people move themselves, but toys need to be pushed, pulled, or carried. She watches a pacifier fall off the edge of the couch and knows it will end up on the floor. And around this age, she's beginning to grasp a concept that will up the fun quotient of your play sessions even further: moving objects displace—that is, bump forward, knock over, or even send flying—stationary ones.
What the Research Shows
Researchers set up a series of experiments in which there were possible and impossible events; in each, moving objects displaced stationary objects. To begin, researchers set a ball rolling down a ramp, which caused a toy at the bottom of the ramp to move.
After watching a few run-throughs, infants (age two-and-a-half months) soon habituated to this event—that is, they became disinterested, as it wasn't anything they were surprised by. To these babies, they were witnessing a clearly feasible event that they knew to be true from their own experiences.
Then the researchers set up a "false device," which they—OK, and we—knew would defy physics: They rolled a little ball down the ramp, which subsequently moved a much larger object. Still, though, these very young babies didn't blink; they didn't find this event as unusual at all.
When six-and-a-half-month-olds were shown the second scenario, they looked reliably longer at the small ball as it displaced the large object. This showed researchers that these older babies were aware that this situation was impossible.
The amazing facts scientists now know? At two-and-a-half months, babies are only interested in the sheer fact that a ball that hits an object makes that object subsequently move (what researchers call "physical causality"), but at six-and-a-half months, babies are keen enough to look at this scenario and take more factors into account:
- the size of the moving object
- the size of the stationary object
- how far—or even if—the moving object can displace the still one