is frequently quoted that upwards of 80% of our taste is made up by smell.
So if you plug your nose and cover your eyes, the taste between an apple and onion should be indistinguishable, right?
The logic makes sense. When I'm home sick, congested and mucus-ridden, eating is often a mundane, muted task. All potato chip flavors taste the same. Chicken noodle soup reminds me of tea with chunks in it. When things are really misty in my nasal cavities, well, you can literally substitute apples and onions and I won't be able to tell the difference.
