Anosmia and Taste

Preface: Taste, Gustation, and Flavor

    I asked one of my colleagues, Dr. Bob Graham, who is an expert in psychophysics (the relationship between physical reality and psychological sensations/perceptions), to critique this web page. His response follows:

In my opinion, arguments about taste and smell are difficult to keep clear unless you upgrade the vocabulary. Start with the ground rule that "taste" will only be used for the five qualities obtainable from the taste receptors of mouth and throat: salt, sweet, bitter, sour, umami. I know of no good evidence for any further taste qualities. All other experiences that one gets from food (or other objects) in the mouth should be referred to as "flavor". Flavor is regarded as the result of gustatory-olfactory interaction. Anosmics can taste quite well -- nothing missing there. But they cannot experience flavor.

    I asked Bob about 'umami,' he replied: Umami is the Japanese name for a taste quality that most researchers now are calling glutamate as it may be specific to that one amino acid (glutamic acid). It is the flavor that puts the zing in soy sauce and spices with MSG. However, I am uncertain whether they really have good cause to limit the taste quality to glutamate when the receptor might be sensitive (perhaps to a lesser degree) to a number of amino acids. The quality might really be a "protein" sensation. The Japanese can lay some claim to naming the quality because they are the ones who spent the lab time on it for all those years when the rest of us were satisfied with just 4 qualities. Now, would someone please identify the "fat" quality receptor on the tongue? My tongue has the darn things and they are Hot-wired into my reinforcement center. When they fire, lights go on all over my limbic system and my right hand reaches for the fork. Surely the little buggers can't just be a figment of my imagination.

    I am quite familiar with the distinction between "taste" and "flavor" made by Bob, and think that such a distinction needs to be made, but it is my opinion that psychophysicists have merely confused the issue by taking a common term, "taste," and giving it a restricted definition, one that is at odds with what almost every one else means when they say "taste." I shall make the same distinction, but with different language. I shall use "taste" and "flavor" as synonyms, and shall use the term "gustation" (a term well known to psychophysicists) to refer to the sense associated with the chemoreceptors on the mouth and throat (which give rise to the sensations salt, sweet, bitter, sour, umami). Psychophysicists may not like this, but I think it will improve communication with real people. After all, when someone says "I add vanilla to my hot chocolate to make it taste better," she is not referring to the minor stimulation of gustatory receptors by the chemical vanillin, she is referring to the powerful (and delightful) stimulation of the olfactory receptors by that chemical. [By the way, you have never really experienced vanilla until you have taken a whiff of the pure chemical -- when I did so, it put me into a vanilla world for a few seconds. My whole existence was vanilla. Yes, it does have a psychoactive effect, as do many of the chemicals that produce powerful olfactory sensations.] Likewise, when someone says "I like peas, but can't stand the taste of pureed peas" he is not referring to a minor difference in gustatory sensations but rather to a major difference in tactile sensations (one of several senses that contribute to taste/flavor). I like oats, but can't understand how my wife eats that slimy mush she makes out of it. I might even like the taste of okra if I could get past the tactile sensation it gives me when I put it in my mouth.

Taste/Flavor in Persons Who Have Never Had a Sense of Smell

    Those with congenital anosmia frequently insist that they have the same sense of taste that those with a normal olfactory sense have. If they were using the word "taste" in the very restricted way that psychophysicists do, that is, referring only to the gustatory sense, I would agree. In fact, I would even agree that anosmic persons might be better able to discriminate among foods on the basis of gustatory stimuli alone than are those with a normal sense of smell but temporarily deprived of that sense -- when comparing the tastes of two foods, they might be able to attend to differences in gustatory stimulation that are, in a person with a normal sense of smell, not noticed because they are trivial in comparison to the differences in olfactory stimulation. But do persons who do not have a sense of smell have the same richness of flavor sensations that those with olfaction have? Of course, they do not, but how can the person who has never had a sense of smell know that? How can someone without a particular sense know what it would be like to have that sense? How could I know what it would be like to have an electromagnetic sense, as some animals do? I cannot -- but I can know both what it is like to be anosmic, and not to be anosmic, because I have traveled between the world of anosmia and a normal (as far as I can know) sense of smell many times.

    Those who have never had a sense of smell frequently make statements like that made by one of my correspondents (I'll call her Liz): "The other misnomer seems to be that if you cannot smell then you cannot taste, which I KNOW is totally untrue." I doubt that Liz was using "taste" with the restricted meaning that Dr. Graham would have us employ. How could Liz know what taste/flavor is like if she has never had a complete sense of taste (not just gustation, but the complex sense which results from gustation, olfaction, tactile senses, and others). As one who has traveled back and forth between the world of sensing odors and the world of anosmia, I can assure you that one's experience of taste without olfaction is nothing like that with olfaction. It is like viewing a rainbow in black and white.

Flavor Discrimination

    Liz replied "However I can Taste if there is no sugar in my Coffee, if food is "off" that is rancid for example. I can tell if there is too much salt in my food etc... If others with Smell and Taste detect more than I do it must something very violent!!"

    I would expect that Liz could detect sugar, rancidness (acidic and bitter), and saltiness, as these are all sensations which rely on the gustatory receptors on the tongue, not on olfaction. I do not understand what she means by "violent." The "itching" in Liz's nose is no doubt due to stimulation of nonolfactory receptors by irritants. When I am anosmic, I rely strongly on such irritants ("hot" spices) to provide me with some sense of taste beyond what I get from the gustatory senses.

    Another correspondent said "I don't think you'd say that a colour-blind person can't see a rainbow just because they don't see all of the colours, or in the same way you do." Of course I would not say that. What I am saying is that the sensation of taste with olfaction is remarkably different than that of taste without olfaction, and since I travel back and forth between the world of anosmia and olfaction, I can know that, and those who have never had a sense of smell cannot.

    Another (Niall) commented "With regards to the taste and smell nexus - I KNOW that I can still taste quite well, but can not smell a thing since incurring a head injury. Though I am certain that my taste is a little different, it is not as extreme a loss as you suggest with your analogy of the black and white rainbow..."

    My reply: "Well, I felt the same way as Niall after I first lost my sense of smell. One gets used to tasting things without olfactory input. But then I had the first surgery which (temporarily) restored my sense of smell. Then I realized that taste without olfaction is, for me at least, really like a rainbow in black and white. You should see me when I first get my sense of smell back after having been anosmic for months (for example when using steroids to restore the sense) -- I just have to taste everything in the grocery store to refresh my memory of what it really tastes like. Many others who have lost their sense of smell think that the "rainbow in black and white" is an excellent analogy. Perhaps this is especially the case in individuals whose sense of smell was very acute and/or valued prior to becoming anosmic.

    So why is it that folks who have never had a sense of smell conclude that their sense of taste is the same as is that of those who do have a sense of smell? The following communication from one of my correspondents (I'll call him Kevin) may shed some light on that question.

    I would agree that a person that can smell would have a greater sense of taste, but I can distinctly taste the difference in almost anything. ex. coke and pepsi, apple and grape juice I can't think of anything that is close but definitely different tastes. Many of the stories on these web sites is that people with anosmia can taste the difference between what is salty and spicy. My taste goes deeper than telling what has too much salt and too much spice. The one thing that I do have difficulty with is fruit flavoured candy. If I don't see the wrapper certain flavours are a mystery to me (blueberry). The article was interesting but I do believe that some people with anosmia can have as strong a sense of taste as someone who can smell. Since I've learned of these sites I have set-up some tests for myself if I'm tasting something that I can or it is something I'm really tasting. example If I see the orange pop I know to expect that flavour or if I take a blind taste test will I be able to tell what I have put in my mouth.

    My response: I am not surprised that Kevin can tell the difference between many (but not all) foods even though he has no sense of smell. I can too when I am anosmic. The gustatory sense is capable of making finer discriminations than might be expected if you think of it as just being able to taste 5 sensations (sweet, sour, salty, bitter, and umami), but think of how many combinations one could construct with various intensities of 5 sensations, each combination representing a different taste. That alone would enable the person who has no sense of smell to be able to discriminate many foods from others. Then consider that the flavour of foods is also affected by the contribution of tactile receptors in the mouth and throat (pureed foods do not taste like intact foods), pain receptors in the mouth and throat (I use hot peppers to make my food tasty when I am anosmic), thermal receptors in the mouth and throat, the sound of the food as it is eaten, what it looks like, expectations about what it will taste like, and on and on. None of these require a sense of smell. The "what it looks like" reminds me of research done years ago at the Univ. of Pennsylvania. Students were offered brownies in their traditional shape or shaped like, well, feces. Guess what, the traditional shape was preferred.

    So, it should be clear that persons who have no sense of smell should be able to discriminate many foods from others, but does that mean that their sense of taste is the same as that of persons with normal olfaction? Of course not, no more than a rainbow looks the same to a color blind person as it does to a person with normal color vision. Consider the nocturnal animal, which has no cones in its retina and thus no color vision, but can nonetheless reliably discriminate between a red stimulus and a green stimulus. How can it do that if it has no color sense? Well, red and green light stimulate the "black and white" photoreceptors (rods) differently -- the green stimulus appears much brighter than the red stimulus. The animal can make the discrimination, but it is not made on the basis of color vision, and the animal does not have an Umwelt (sensual/perceptual world) like that of an animal that does have color vision. I argue that taste for the anosmic is like vision for the nocturnal animal -- many discriminations can be made, but they are not based on a full sense of taste -- and the anosmics cannot possibly know that, unless they have their sense of smell restored. Also, people with a normal sense of smell really cannot appreciate how much it contributes to their sense of taste unless they have completely lost it for an extended period of time and then get it back again. Those who have, as have I many times, can speak from personal experience.

    One final note, regarding the Coke versus Pepsi discrimination. While I do not deny that Kevin may be able reliably to make this discrimination, I should add that many persons with normal olfaction claim to be able to make the discrimination but when tested under double-blind conditions, their discriminatory power is found not to be reliable. Think about it -- if there really were dramatic differences in the taste of Coke versus Pepsi, would these companies spend so many millions of dollars trying to get us to choose one over the other?

    Another correspondent (Joel) opined: I can understand this viewpoint, and I certainly agree with its validity to the extent that olfaction certainly is entirely beyond the experience of congenital anosmics (such as myself), and consequently we cannot say what the experience of smell is like. It does not follow, however, that our experience of chemosensory phenomena is no different from normal gustation when it is deprived of normal olfaction. The very fact that we have no experience of smells means that our schema's of "taste" are entirely different from someone who has developed with a fully-operant sense of smell, even if they subsequently lose it. Not having a sense of smell is not the same as having never had such a sense, and though there are certainly parallels in our experience, there is not necessarily a 1-to-1 correspondence. Therefore, respectfully, Karl, I do not think that you are in the best position to appreciate the experience of the congenital anosmic. Certainly, we do not have the capacity to perceive flavor--that much is clear. But our gustatory sense may be far more perceptive than yours, and there may well be other differences, as a number of postings on this board might lead one to think.

    My response: Agreed, and well stated. It certainly would be interesting to find a case where a person was anosmic from birth but gained a sense of smell later in life, after the development of gustatory schema - but lacking such a case, the best we can do is share our experiences and speculate regarding what the other perceives. I can add that I was anosmic for many years before I had the surgery that restored my sense of smell, and those years of experience without olfaction did not modify my gustatory sense to the extent that taste without olfaction was anything like taste with olfaction. Of course, there could be a 'sensitive period' phenomenon operating here -- that is, one's gustatory perception may be influenced by a lack of olfaction that starts early in life but not by (or not as much by) a lack of olfaction that starts later in life -- I had apparently normal olfaction early in life.

    Joel suggests that taste (gustation) in a person who has been anosmic from birth is different than taste in a person who is anosmic now, but who has had, at some time in the past, a functional olfactory sense. Accordingly, Joel argues that nobody but a congenital anosmic can understand what the sense of taste is like in a congenital anosmic. Do note that Joel's interesting argument includes the supposition that the gustatory sense (taste) and the more complex perception of flavor, is not the same in congenital anosmics as it is in those who have had an olfactory sense at some point in their lives. Joel argues that having never experienced olfactory sensation, the congenital anosmic's brain develops a different interpretation of the gustatory sense than does the brain of a person who has had olfactory experience. Joel suggests that the congenital anosmic develops a "more perceptive" gustatory sense than that in a person who has experienced olfaction. This argument is similar to that commonly made with respect to compensatory abilities involving other senses in blind persons -- that is, the blind person learns more effectively to use information from his or her other senses, to offset the lack of vision. Until recently, the majority opinion of scholars has been that this is a myth, but there is now some evidence that (partial) sensory compensation may, indeed, be a fact. You can find a summary of recent research at Sensory Compensation.

    Please note that Joel did not suggest that compensatory processes allow the person with congenital anosmia to experience the flavor of foods in the same way that persons with an olfactory sense can. His suggestion was that persons with congenital anosmia may learned to use gustatory information more effectively than do persons who have an olfactory sense, and this suggestion is a quite reasonable one given the recent research on sensory compensation. An interesting test of Joel's hypothesis would be to compare the performance of persons with congenital anosmia with that of persons who are temporarily anosmic on a task that involves discriminating different foods from one another. To the best of my knowledge, no such research has been reported in the literature. There would some serious technical problems with producing the temporary anosmia -- for example, simply plugging up the nose would not do, since odors from ingested foods may reach the olfactory receptors by traveling up from the mouth.

    Again, let me note that the current research on sensory compensation does not suggest that sensations that would normally be produced by one sensory system can, in a person without that sensory system, be produced by a different sensory system -- but technological advances may someday allow this to be the case after devices are implanted into the brain, devices intended to produce the same sort of sensory information that is produced by the missing system.

    Perhaps it would be interesting to consider a similar case with respect to color vision. Graham and Hsia (Unilateral curves for normal and dichromatic subjects including a case of unilateral color blindness, Science, 1954, 120: 780). reported a case of a woman who was red-green color blind in one eye, but had normal color vision in the other eye. Let us call her Suzy. It has been argued that Suzy could use the one eye to see the world as a person with normal color vision does and the other eye to see the world as a person with red-green color blindness does. She described the world seen with red-green color blindness as being black, white, and shades of yellow, blue, and gray, with absolutely no sensation of redness or greenness.

    Now suppose that a man (Jake) with red-green color blindness in both eyes has listened to Suzy explain her experiences. Jake says to Suzy, "you think you can look through that one eye and see what I see with both of my eyes, but you are mistaken. Because you have had the experience of normal color vision in the other eye, your brain has not developed the same as has mine. My compensatory brain development allows me to see the world with as much variety and richness of color as that in the world you see with your so-called normal eye."

    Now I ask you, do you still believe the assertion that Suzy can, with her one color blind eye, see the world as does Jake with both of his eyes? Behaviorally we can distinguish the color blind person -- I suspect most of you have seen the little diagrams which have symbols on them that a person with normal vision can see but a person with color blindness can not -- but how can we argue with Jake's assertion Suzy cannot really describe what colors look like to Jake?

    After you and I listen to this conversation between Suzy and Jake, I turn to you and say, "you know, the mental experience I get when I look at something red is not at all like that you get when you look at something red -- sure, we both call that stop sign over there "red," but the raw feel of redness in my mind is distinctly different than the raw feel of redness in your mind -- in fact, the raw feel I get when sensing redness could well be like the raw feel you get when sensing blueness, or maybe even like the raw feel you get when smelling vanilla, or hearing a pure 100 Hz tone or being tickled or who knows what."

    We may well be wasting our time trying to figure out what another being's mental life is like -- how can we ever really know? I suppose that is why my profession turned away from such phenomenological investigations many years ago.

Anosmia and Eating

    Regarding the effect of anosmia on eating, I think it not simple. Sometimes I think that I eat too much when anosmic because I lack the "afferent inhibition of hunger" provided by the sense of smell (tells your brain that you have eaten, so you can reduce your need to eat even though the nutrients have not yet been absorbed from the gut). But when I get my sense of smell back, food tastes so very much better that I eat and eat just for the enjoyment of it, and recognizing that I can loose it again any moment.

Who has it worse, those who never had it or those who had it and lost it?

    In correspondence with another congenital anosmic I noted that an interesting topic among those with anosmia is whether congenitals or those who lost their sense of smell have it worse. I really think it is a toss-up. Those of us who lost it really know what we lost, but at least we have the memory of how great it was -- and I have the prospect of getting it back for a while by surgery or steroid treatment. I may be somewhat unusual in being one who travels back and forth from the world of anosmia and that of a normal sense of smell -- but who else would be better qualified to tell others what it is like to be anosmic and what it is like to have a normal sense of smell. In a way, I am like one case well know to psychophysicists, a woman who is (partially) color blind in one eye, but has normal color vision in the other (see Graham, C. H., and Hsia, Y. Luminosity curves for normal and dichromatic subjects including a case of unilateral color blindness, Science, 1964, 120, 780). She was able to tell us what it is like to be color blind, because when she views the world through the one eye, she has normal color vision, and when using only the other eye, she is color blind. Thus, she can view the world as a color blind person, but knows what it is like to have normal color vision. She was red-green color blind, and told us that with the color blind eye the world was all shades of black-gray-white and yellow-blue, absolutely no sense of red or green. Of course, if she did not have a "normal" eye, she would not know that what a person with red-green color blindness sees is any different from what a normal person sees. In the same way, a person who is and has always been anosmic cannot know what it is like not to be anosmic, but I can.

Beyond Psychophysics

    If despite all the evidence to the contrary, an anosmic person clings to the delusion that he or she can sense the flavors of foods as well as can a person with a normal sense of smell, then we are dealing not with psychophysics but another branch of psychology -- that branch in which denial is known as an effective ego defense mechanism. Denial is not my own personal favorite defense mechanism, but I am not about to deny that it is one which I employ myself.

   This denial is sometime accompanied by other distortions of thought and emotion.  For example, consider this post that appeared on the Yahoo anosmia group:

    In fact, since we can taste from our tounges, <sic> most anosmiacs can at  least taste 4 things. Someone wrote about this a while back. If you think about it, 4 things times 4 combinations. If my calculations are right, we can actually taste 16 things. NOt as good as 40,000 tastes or whatever those smelling bastards can make out but still...

    The combinatorial math is incorrect, and it is also incorrect to assume that tasting one quality (sour, for example) is a dichotomous event.  I would also point out that the marital status of one's parents is probably irrelevant.

Can This Question Be Answered?

     A journalist from the Philippines asked me for suggestions regarding how she could research the question “do people with anosmia have the same richness of flavor sensations as those with olfaction?”  My response to her was:  Your research question is very interesting, but will be difficult to address empirically. What you cannot do is ask people who have congenital anosmia and those who do not to evaluate the richness of their flavor experience, since those who have never had olfaction have no idea of what is absent in their sensory world. Ideally you would be able to obtain data from two critical types of persons:

  1. Persons who have been anosmic since birth, but for whom a treatable cause of their anosmia has been found. You would then question them about how their experience with flavors changed after successful treatment. It will be very hard to locate these people.
  2.  Persons who have had normal olfaction since birth but now have lost it. These will be much easier to find.

    Also useful would be information from persons who have lost their sense of smell, then gained it back after a considerable period of anosmia.

    Another approach would be to do some basic psychophysics on both persons with congenital anosmia and those with normal olfaction. What I have in mind is an objective testing of the ability of persons in each group to discriminate between foods of different flavors. I would start by identifying several foods which anosmic persons can reliably discriminate, and then determine if persons with a normal sense of smell can also (I expect they would). Then you need to identify several foods where olfactory sensation is expected to contribute to the flavor of the foods and then test both anosmic persons and those with normal olfaction on their ability to discriminate between the two.

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This page most recently revised on 29-December-2019