Memory is one of the most interesting things to study, especially testing to see how much infants can remember. As adults, most of us have infantile amnesia, which is the inability to remember early memories, usually before the age of three. However, that does not mean that infants can't remember earlier memories!

Researchers attached a string to the infant's foot and a mobile in their crib. Using instrumental conditioning (a learning process that links behavior to a consequence), the baby learned that if they kick their foot, the mobile above them will move.

Once the infant learns they can make something interesting happen (the mobile moving) they do it constantly to entertain themselves. The researchers also made sure to measure the baby's kicking without the mobile to make sure the infant doesn't just like to kick their feet a lot. Results showed that two month old babies can remember how to do this for a full twenty-four hours later, and six month old babies can remember up to two weeks later!