Just as scientists are reexamining the basic tastes, they are also redefining the tongue map. The tongue map breaks the tongue down into regions of sensation -- bitter in the back, sour on the sides, salty on the front edge and sweet at the tip. Umami researchers have claimed that the tongue's posterior is important for detecting the fifth taste.
But for everyone who remembers arguing the tongue map as a grade-schooler, insisting they could perceive salt at the back of the tongue or sour at the tip, news that the tongue map is flawed at best must come as sweet vindication.
A German scientist named D.P. Hanig developed the tongue map in 1901 by asking volunteers where they could perceive sensation. Other scientists later corroborated his findings but charted the results in such a way that areas of lowered sensitivity looked like areas of no sensitivity. By 1974, Virginia Collings determined that while the tongue did have varying degrees of sensitivity -- some areas could perceive certain tastes better than others -- there was no real truth to the strict tongue map. Although taste receptors usually react strongly to a single taste, many respond to multiple gustatory stimulations. People can perceive taste anywhere there are taste receptors.
Scientists are also learning more about the shocking diversity of taste sensitivity. In the next section we'll learn about an acute sense that you actually might be glad not to have.