As explained in this article on Tabasco sauce, there is an objective, scientific way to measure the spiciness of foods; peppers or hot sauces subjected to this test get a rating in Scoville heat units. Unfortunately, these measurements are never used where it counts: on menus in Mexican, Szechwan, and Thai restaurants. The menus sometimes have little chile symbols, or sometimes just asterisks, that are supposed to indicate how spicy a dish is. But these symbols are arbitrary, they vary from one restaurant to the next, and they are nearly always (in my experience) meaningless.
Even worse: the suggestion “Specify desired level of spiciness.” I do, but they never take me seriously. Maybe I just look like some lightweight gringo who can’t handle his capsaicin, but no matter how spicy I order my food, it’s almost never even hot enough to make my eyes water, which is beginning to approach “hot enough” in my book.
A case in point: One day I went to a Thai restaurant and ordered the dish on the menu with the most chiles next to it. The waitress asked how hot I wanted it. I said, “Extremely hot.” She looked at me with a concerned expression. “Extremely hot?” she asked. “Incredibly hot,” I replied. The concerned expression turned to a puzzled, worried look. “Wait a minute, do you want it extremely hot or incredibly hot?” Clearly, we were experiencing a communication failure.
I tried a different tactic. “I want you to make it as hot as it possibly can be,” I said. The waitress paused for a moment to let this sink in, then gave me a horrified expression, as though I had just asked her to set me on fire. Finally, she said, slowly, “You mean…like death?” “YES!” I exclaimed, delighted that my message had finally gotten through. “Hot like death. Exactly. Please.” She regarded me severely for another moment, wrote something down on her pad, and disappeared into the kitchen.
When the dish arrived, it was noticeably spicy—I’m going to go out on a limb and say maybe two out of four peppers. But not death. Not even “pass-the-hanky” hot. What a disappointment.