When you consider the tongue, what leaps to mind are the five canonical tastes – sweet, salt, bitter, sour, and umami. These sensations arise when receptors on the surface of taste bud cells are activated by your food, triggering nerve fibres that run to your brain and help generate the experience of a savoury roast or a fresh strawberry. But your tongue is more versatile than that. It's also sensitive to temperature, pressure, and chemicals that mimic both of these things, which turn up in a number of foods. This peculiar latter group of sensations is called chemesthesis, and you probably experience some flavour of it every day.
One of the strangest examples is the Szechuan peppercorn, a staple of Asian cooking. You know when it's been sprinkled over a dish because suddenly your mouth begins to tingle gently, while going curiously numb. A compound known as “sanshool” is responsible. It turns out that sanshool binds to channels in the membranes of neurons in the tongue that respond to touch, producing a kind of tactile mirage.