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There’s no accounting for taste

When I was in early grade school, I was placed in a program called “Enrichment”, where because I was too smart for my own good and was disrupting classes’ ordinary learning-flow, I was taken out of the “easy” classes and taught separately about topics of my choosing.  I believe the first of my chosen topics was the human body — I wanted to know all about how the various cogs and gears fit together and worked in unison.  One of my first scholastic memories involves being corrected on the spelling of “away” on my labelling of the ventricles of the heart, in fact.

Another of my earliest scholastic memories involves a further module in this same topic, wherein I was taught where on the tongue the taste buds for various types of tastes were located.  They even devised an illustrative experiment where they had a series of little unmarked bottles with eye droppers and clear liquid, and used the eye droppers to place a droplet of one type of liquid or another directly on different spots on my tongue.  The teacher was surprised when I recognized the tastes regardless of where they were dropped, but then hand-waved it off proclaiming that it must have been because the drop spread out across my whole tongue.  The fact that this experiment didn’t work out as planned has stuck in my mind since then, as it was one of the first times I was exposed to the concept of experimentation used to prove or disprove dogmatic beliefs.

sciencemotivator-tonguemapOf course, some years later, I discovered that the commonly held folk-wisdom that there were four delineated taste-regions was completely and wholly without any scientific merit whatsoever (never mind that we recently also discovered umami is separate and distinct from sweet, bitter, sour and salty, meaning the map originally made by D P Hanig would have had to be revised).  What sticks in my craw to this day is, the teacher was presented with evidence through experimentation that challenged her dogmatic belief that the taste buds were localized, and yet rather than stirring her curiosity or leading to a real experiment with proper scientific controls, or with overturning the commonly held precepts of taste bud maps, she simply waved it off with a facile explanation invented from whole cloth.

Science, as you must know by now from my myriad postings on the topic, is subject to revision when new evidence comes along that refutes the hypotheses of the day.  There is no scientific “belief system”, you do not take science on “faith”, and you do not accept scientific “dogma”.  You can trust that the theories postulated by scientists are well-evidenced and make testable predictions that have been borne out, but you should never take what someone says as dogmatic truth without being presented with that evidence or those tested predictions.  Also, if you have evidence that refutes a theory, that theory is (rightly) overturned and after new hypotheses are postulated and experimented against, a new theory that better fits the facts is created.

So that’s the story of how it will likely bother me to the end of my days that I was taught folksy bunkum in my “enrichment” program, and will forever question pretty well everything I’m expected to believe by rote.  I hope you learn from my lesson.

Comments

  1. caroline says

    part of my tougne was numb for a good month once and I couldn’t taste sweet stuff, how do you explain that then my scientist :) Mind you it was the right side of my tongue not the front like the picture indicates…

    but really if you have an answer that be great, no one could figure it out.

  2. says

    Caroline!  Awesome!  I *knew* I had some Torontonians reading me, glad you’re one of them.

    Obviously I can’t “answer” this one — we have no way of proving any hypothesis I might make, since your tongue is long since back to normal.  However, I CAN tell you more about how your tongue detects different tastes, and maybe that’ll help some.

    Salty and sour are handled by ion channels, which are proteins that can recognize and distinguish between voltage gradients across cells.  They exist in the cell membranes of all biological cells, and are especially prominent in the nervous system, apparently acting to “gate” certain neuron impulses.  Sodium ions (and other alkali metals) pass directly through them, “activating” those neurons that detect saltiness.  Same with sourness, only hydrogen ion channels are activated by hydronium ions. 

    Sweet,  bitter and umami are handled by G protien coupled receptors (GPCRs).  They’re trans-membrane receptors, meaning they can detect something outside a cell, and activate responses within the cell.  Each of the various tastes can be received by certain receptors that use GPCRs in conjunction with whatever function they have.  Bitter can be detected by T2R’s (“Taste-2 Receptors”).  Sweet registers using the T1R2+3 (heterodimer) and T1R3 (homodimer), and can only work if both of these receptors are triggered in sufficient quantity.  Umami (like MSG) triggers certain umami taste buds in the same way as the sweet receptors are triggered, and the taste is increased by the presence of salt (why meat tastes better when salty or spiced).

    And now I’m getting to the limit of my understanding of the Wikipedia articles I read for this reply.  But I figure whatever shock your tongue underwent after being numbed (you didn’t say how — dentist visit?), it ended up affecting the receptors for sweet without affecting any of the others.  Considering how differently each taste is detected, it doesn’t surprise me that one could be knocked out without hurting the others.  One really cool thing about the way you taste stuff is that we’ve actually discovered a berry that totally rearranges how our taste buds detect certain foods, such that sour things magically taste sweet.  The fact that something like eating a berry could drastically alter the shape of our taste receptors leads me to believe that whatever trauma your tongue had, actually managed to mess with its sweet receptors.  Are you sure you didn’t have any other taste weirdness from it?

  3. caroline says

    wow it’s 7 in the morning and that just blew my brain. I hope I will be able to recover for the rest of the day.
    I have no idea how it happened it just did.  I was just leading my everyday normal life.  It may have been the smoking?  Before that happened my tongue would sometimes feel “off” after a smoke.  I still get the feeling every now and again, but no numbness since that month of just plain cruelness.
    I may have had other taste weirdness, but I didn’t really notice it just made anything that had sugar in it basically taste like assssss.

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