We all had a family doctor who had this amazing ability to predict how long a fever would last, that too without conducting any medical test. Similarly, an experienced cook is able to tell the quantity of ingredients required to make a dish for an event. A tailor can tell the length of cloth required to stitch a suit by just looking at the body structure. Even before Google maps came into existence, an experienced cab driver could have given you a fair estimation of time required to reach a particular destination, that too for different hours of the day. And a good fielder is able to take a running catch without first calculating the trajectory, speed and direction of the cricket ball.