I have just discovered Wikipedia’s page on a ‘List of common misconceptions’ that includes, among many other wonders, a great piece about the myth of the tongue taste map.
Different tastes can be detected on all parts of the tongue by taste buds, with slightly increased sensitivities in different locations depending on the person, contrary to the popular belief that specific tastes only correspond to specific mapped sites on the tongue.
The original tongue map was based on a mistranslation of a 1901 German thesis by Boring (an eminent psychologist at Harvard). In addition, there are not 4 but 5 primary tastes. In addition to bitter, sour, salty, and sweet, humans have taste receptors for umami, which is a savory or meaty taste.
You can see the referenced entry here and there’s much more joy on the complete page of misconceptions.
UPDATE: Thanks to commentors Steve and Vinnie for pointing me in the direction of the latest XKCD comic that mentions the ‘common misconceptions’ page. Not my source but a wonderful reference point!
Link to Wikipedia ‘List of common misconceptions’.