When baby rhesus macaques start to gain independence from their mothers, they don’t just do as baby birds do and jump out of the nest for good, never to return. They have this behavior we like to call a “check-in”. Basically, a baby will run around and explore its surroundings alone, then when he gets afraid or uncomfortable, he’ll scurry back to his mom just to let her know he’s OK and to make sure she’s still there.
As of September 21st, 2011, the popular website Four Square reached 1 billion “check-ins”. Four Square is a social networking site that allows its users to let others know where they are, as long as they connect with their smartphone or other GPS-enabled device.