There are some people who have interests in only some narrow field, and are not interested in anything else:
- physicians who heal only ears, and for whom the stomach doesn't matter
- clerks who know all the fiscal laws by heart, but ignore anything that isn't written there
- fanatics who care only what the scriptures say
- housewives interested only in cooking and soap operas
- geeks who care only for computer games and comics
- crazy scientists that know everything about chemistry but don't know who Columbus was and have probably never heard of America
What do I call someone who has such narrow-field interests and/or knowledge?