Introduction. The are many situations in life when we must rapidly learn a lot of new things. Children learn that squiggles shaped like "R" make the /r/ sound, and squiggles shaped like "P" make the /p/ sound. Adults learn that certain flavors of wine are called "merlot," but other flavors are called "burgundy." Physician learn than certain combinations of symptoms are one disease, but a different combination of symptoms are a different disease.
Try it yourself. Suppose you are a new clinician learning to classify case histories of patients into disease categories. You see a list of symptoms, make your best diagnosis, and then the expert physician tells you the correct diagnosis. Gradually you learn what symptoms correspond to what diseases. You'll be doing a simple learning task like this.