Using a method called violation of expectation, where babies are shown photos, videos, and events that come as expected and then followed by some that break rules or are unusual, the babies gaze is followed as a child will usually stare at images that are surprising. But the question as to what age a child starts to understand how the physical world works remains.
“We believe that infants are born with expectations about the objects around them, even though that knowledge is a skill that’s never been taught. As the child develops, this knowledge is refined and eventually leads to the abilities we use as adults,” said Kristy vanMarle, an assistant professor of psychological sciences at the University of Missouri.
vanMarle and Susan Hespos, who is a psychologist at Northwestern University, looked through all researches on infant cognition over the last 30 years to determine the answer to their question. It was found out that as soon as the baby enters his first two months of life, he is already able to have an intuitive understanding of some physical laws. This is also the same time that they are able to track moving objects with their eyes. An example of this is that children have the knowledge that objects will never float but will fall without support. They also understand that an object that is hidden does not cease to exist but only cannot be seen.
It was also found out by the same research that children also have rudimentary math abilities. As early as the child reaches 6 months, he or she can already determine which group of dots has more dots in it. Meanwhile a 10-month-old baby can already distinguish which cup contains more liquid.
Source : http://www.huffingtonpost.com/2012/01/25/babies-physics_n_1230699.html