Sensitivity of Taste

I found a great blog written in Japanese by Mr. David, an American studying Japanese. I was amazed by his language skill and amused by all of his posts.
In this post, he is wondering why the Japanese describe both salty and spicy taste by the same word "KARAI". It's strange to us, too. And it gave me a good opportunity to think about our sensitivity of taste.

We write the word "KARAI" with kanji as. This kanji has another pronunciation "TSURAI", with the meaning of "to be hard or painful". I think its meaning is very similar to "bitter", it is the name of another different taste though. "KARAI" is also used to express being strict to judge, and you say "bitter judgement", right?
Conversely, "to be loose to judge" is expressed as(AMAI). It also has meaning of "to be sweet". Seeing that an English word "sweet" also has the meaning of "beautiful" or "kind", maybe the sweet taste is welcomed by all of the world.

And I assume that spicy taste would be the most disliked taste by the Japanese, not "bitter". Of course there are a lot of ethnic restaurants in Japan and many people love spicy food. But we can hardly find any spicy food in traditional Japanese food except sushi with too much WASABI. Isn't it because our sensitivity of taste is more acute than foreign people? We love food which have no strong taste like rice or tofu, don't we? So we would express too salty taste as the same word as spicy, right? Who am I asking? So I tested it with my own tongue.

Look carefully at these four beer cans. What do you think the differences between them are? They are almost same, but each of these beer is made of different kind of water from different areas in Japan. Do you know any other countries that make this kind of sensitive things? Only we are supposed to be able to find out those subtle differences of water with our delicate tongue! I opened all pull tabs and sipped them alternately.

Nothing different! They were completely the same to me! The four cans of beer brought me nothing but a hangover. Who cares about the difference of the water in beer? Forget about my assumption above. We're only sick!