They can be expected to engender both in lay people and in specialists a sense of respect that, even when tempered by scepticism, is greater than respect accorded to mere qualitative descriptions. Therefore, when one opts to use numbers, one incurs a greater responsibility to provide evidence than if one uses a less quantitative estimate. In the case of the aforementioned claims, the issue is not whether the correct percentage is 90 versus perhaps 92 or 88, but whether it is anywhere near 90, as opposed to near 50, for example.
Here, though, it is perhaps important to stress that the focus in this piece is on flavour perception rather than the entire multisensory eating experience where the sensory balance is undoubtedly quite different [ 2 ]. The final conclusion that Sivak [ 3 ], p. For the publications that cite other publications in support of such claims, the finding is the same: the final publications in the citation trees offer no supporting evidence.
The implication is that we researchers have been a too lax about citing others, without checking for supporting evidence, and b too eager to appear more quantitative than the evidence allows. As so often turns out to be the case, though, when one eventually traces these things back to their roots, the original authors cited in support of this particular figure, never said quite what everyone since has quoted them as saying! A little closer to the theme of the present article, another claim that is often made in the literature on the chemical senses is that there are 30, smells.
In the introductory chapter to his excellent book, What The Nose Knows , Avery Gilbert attempts to trace the origin s of this claim. Once again, the underpinning data needed to support such a claim is, in fact, simply not there. Estimates of odor diversity lead either to a dead end or to Ernest C.
The comfortable, often-cited figure of 10, smells is, from a scientific perspective, utterly worthless. In fact, as reported by scientists last year in Science , the true figure in terms of the number of discriminable smells may be much closer to one trillion [ 20 ]; see also [ 21 ]! However, the statement has absolutely no basis in scientific fact [ 22 , 24 , 25 ].
The fact that the various claims listed above do not cite a reputable source is not necessarily problematic if one can find solid empirical data to support such a claim. It also serves to mask the underlying confusion amongst scientists and philosophers concerning how best to define taste and flavour [ 27 ].
Anyone wishing to evaluate the veracity of such statements faces a number of substantial challenges:. Foremost amongst these challenges is the fact that no one can agree on quite how to define flavour see [ 27 — 29 ]. Part of problem here is to discriminate between sensory inputs that merely modulate taste and those that are constitutive of it [ 30 , 31 ]. As Bakelar [ 32 ], p. Sure, vision and hearing can radically change the perceived taste of food and drink, but that does not necessarily mean that they should be deemed as constitutive of it.
Until we know which senses are, in fact, constitutive of flavour, and which should be excluded because they are merely modulatory , it is obviously going to be rather difficult to assign a precise contribution of each one to the overall flavour experience.
Footnote 6. However, as we will see below, things are still not going to be easy for a number of reasons. The relative contribution of the senses to our experience and enjoyment of food and drink would seem to vary quite considerably depending upon the particular food that is under consideration. The olfactory contribution of sushi, say, seems to be much lower than its contribution to our enjoyment of a ripe French cheese.
This important chemical sense is easily overlooked in considerations of taste and smell, because it has received less experimental study than the classical taste and smell modalities. Footnote 7. However, matters soon become complicated here for as Lawless [ 38 ], p. This blurring is perhaps worst in the sensations of astringency.
Tannins in foods are chemical stimuli [hence meaning that they are constitutive of flavour], and yet the astringent sensations they produce seem largely tactile [which would imply that they were merely modulatory]. They make the mouth feel rough and dry, and cause a drawing, pucker, or tightening sensation in the cheeks and muscles of the face Bate Smith, Should the decision be based on the physiology or the phenomenology?
The jury, it should be said, is still out here. Given such concerns, one could, of course, retreat still further, and just take the case of flavours that have no obvious trigeminal component. However, as we will see below, even in such a restricted case, we run into problems. It is at this point in our discussions, though, that it may be worth looking a little more closely at what is likely the underpinning research that inspired many of the claims one finds nowadays in the literature.
Specifically, Murphy et al. More specifically, the participants were given a series of solutions to taste, and they had to rate the intensity of the odour, the taste, or the overall solution using a magnitude estimation procedure. The participants were given solutions containing only the tastant, solutions containing only the odorant, and solutions containing a mixture of the two. Intensity ratings for the mixture were slightly lower than would have been expected based on the summed response to each of the putatively unisensory stimuli.
Here, it is worth quoting at length, the passage from Murphy et al. Subjects ascribed little odor magnitude to solutions containing only sodium saccharin, but ascribed considerable taste magnitude to solutions containing only ethyl butrate.
Subjects seem to resolve ambiguity regarding the locus of mutual olfactory—taste stimulation in favour of taste. It is at this point that questions about the particular combination of olfactory and gustatory stimuli used become relevant [ 39 ].
Murphy et al. Stevenson and his colleagues have shown that certain odours, such as, for example, a caramel odour could simultaneously enhance sweetness while at the same time suppressing sourness [ 41 ]; see also [ 39 ].
Footnote 9 Hence, the relative contribution of olfaction and gustation to a tasting experience is crucially going to depend on how regularly the component stimuli have been experienced together previously. One suggestion is that it is only when the olfactory and gustatory stimuli are congruent, i. In other words, it may only be under conditions of oral referral that we believe that smell is contributing significantly to the tasting experience that is flavour perception.
Interestingly, the extent of oral referral to the mouth depends on the congruency between the olfactant and the tastant [ 42 , 43 ]. The suggestion, then, that has been made by commentators is that the effect reported in Murphy et al. Are we talking about orthonasal olfaction i. The former certainly plays an important role in the setting of taste and flavour expectations [ 48 , 49 ], and hence plays only a modulatory role, while the latter is thought to be constitutive of flavour experiences.
Importantly, however, these two types of olfaction recruit somewhat different neural substrates when it comes to the representation and processing of food odours [ 50 ]. It is ironic, then, that the Murphy et al. Footnote 10 As such, the claim would seem to be based on research involving the contribution of both modulatory orthonasal olfaction and constitutive cues retronasal olfaction to flavour. As McBurney [ 27 ], p. All of these contribute to flavour.
Footnote 11 After all, every one of us says that we enjoy the taste of the food, when what we really mean to say is that we enjoy its flavour. As Bartoshuk and Duffy [ 53 ], p. Authors also sometimes switch back and forth between different meanings of the term taste , adding further to the confusion.
This is where I start to become confused. By the four basic types, Korsmeyer presumably means the four basic tastes—namely, sweet, sour, salt, and bitter though note that umami is now regularly being included in lists of the basic tastes. Footnote 13 By contrast, flavours, at least as commonly understood, include many of the more interesting qualities of food, think fruity, floral, herbal, meaty, burnt, smoky, etc.
It is only hidden away on page 3 that the author acknowledges that she intends to use the terms taste and flavour interchangeably. The fact that certain olfactory stimuli, such as vanilla, caramel, or strawberry aromas for those in the west, can also modulate, or perhaps even give rise to, the perception of sweetness in an otherwise tasteless solution puts pressure on the definition of taste [ 40 ].
In this case, a person might have a flavour experience with a distinctive taste component even though no tastant was actually present though some tactile stimulation would likely be needed in the oral cavity to give rise to the requisite oral referral to the mouth. Examples would be sugar and salt. In particular, given recent evidence concerning the existence of cells with taste receptors in the gut, respiratory and gastro-intestinal tracts, and elsewhere see [ 57 , 58 ] , the definition should also stipulate that stimulation of the gustatory receptors in the oral cavity is required [ 59 ].
What role attention? In many areas of our daily lives, what we perceive and are aware of depends fundamentally on where our attention happens to be directed, either endogenously voluntarily or exogenously i.
If so, the percentage of taste that is contributed by smell might be expected to vary as a function of the attentional state of the observer. Stevenson [ 63 ] has been doing some of the most detailed thinking in this area. However, flavour binding would appear to make it especially difficult for people to covertly attend [ 64 ] to just one element of an integrated flavour gestalt [ 65 , 66 ].
Indeed, this inability to pull apart sensations based on attention has also been stressed by Smith [ 67 ]. One final source of evidence that would seem potentially relevant to this debate concerns the consequences of the absence of sense of taste gustation or smell olfaction on multisensory flavour perception. In the case of olfaction, the absence of olfactory sensation what is known as anosmia can either be congenital [ 68 ] or acquired i.
By contrast, I am not aware of any congenital form of aguesia. In those cases of late-onset taste loss, resulting from the removal of the tongue [ 70 ] or following herpes [ 71 ], those so affected have reported surprisingly little loss of sensation though see also [ 72 ] for a chef who lost the ability to taste following treatment for tongue cancer.
When it comes to anosmia, the results would appear to depend on when exactly the loss occurred. Congenital anosmics appear to adapt reasonably well, whereas when the loss of smell occurs later in life typically the result of car accident or viral infection appear to dramatic changes in food appreciation [ 73 ]. The answer may also change somewhat as a function of how far into a meal one is as well, given possible consequences of olfactory loss for sensory-specific changes in satiety [ 74 ]; though see also [ 75 , 76 ].
Studying those individuals suffering from a selective loss of trigeminal sensation would also, potentially, be interesting here. It is, however, important to note that drawing any simple conclusions here concerning the relative importance of smell and taste to flavour perception, based on the loss of one of the flavour senses, is made all the more difficult by the cortical plasticity that may occur in such cases [ 67 , 77 ].
However, in the majority of such cases, no specific evidence is cited in support of the claim. What is more, the only article that is, on occasion, cited—specifically, Murphy et al. In fact, I would be tempted to argue that it is pretty much meaningless to try and put a precise value, or even a narrow range of values, around the relative contribution of olfactory cues to multisensory flavour perception.
Given that there is little consensus regarding quite how flavour should be defined specifically regarding which of the senses play a constitutive and which a merely modulatory role delivering a precise verdict is some way off yet and would anyway carry with it a whole host of assumptions.
Researchers should, then, perhaps be more cautious about propagating such explicitly quantitative but unsubstantiated and possibly unsubstantiable claims see also [ 78 ]. As Sivak [ 3 ], p. By verifying what we cite we would minimize the chances that unjustifiable but plausible claims become enshrined in the literature.
Here, though, we should also not forget the role of the gustatory system in visceroception, interoception, and hedonia although coded in a more subconscious way; [ 79 ]. Nevertheless, even without being able to put a precise value on the contribution of olfaction both orthonasal and retronasal one presumes to our expectations and experience of food and drink, most researchers do seem happy to agree that the pleasure, all the interesting dimensions of what is commonly called taste, the meaty, the floral, the fruity, the herbal, the citrus, the burnt, all derive primarily from the contribution of olfaction.
Footnote And this is perhaps never more challenging than when it comes to weighing up the relative contributions of the constitutive flavour senses of gustation, retronasal olfaction, and trigeminal stimulation. The work of a number of modernist chefs, culinary artists, and designers in recent years can be seen as playing in precisely this space see [ 2 , 72 ], for a number of such examples. So, for instance, a growing number of chefs have started to deliver an olfactory component to their dishes through the use of aromatic plateware, through the use of atomized sprays over a dish.
A number of chefs, culinary artists, and companies have also started to deliver an additional aromatic element to a dish through the use of scent-enabled cutlery see [ 81 ] for additional examples. Of course, one of the problems here is with the way in which the press abbreviate what the academic says. However, the ensuing article will typically abbreviate the quote to read Prof. Smith assures me personal communication that he indeed prefaced his statement to The Financial Times in this way.
Note that this is by no means meant to be an exhaustive listing. There are many other examples of a percentage being given in academic and popular press articles: there are many more examples of commentators suggesting asserting? Leading Gilbert [ 18 ], p. Stuckey [ 15 ], p. What about the other three? When you add the influence of touch, hearing, and sight, things get really interesting.
First, while I accept that crying in response to the sting of the onion is mediated by the trigeminal system, I am not so sure I want to call it part of the flavour experience. Second, and highlighting the complexity associated with working and theorizing in this area, while carbonation was traditionally considered primarily a trigeminal stimulant e.
And confusing matters still further, Di Salle et al. It should be noted, in passing, that in many languages, the same term is used for both taste and flavour. The suggestion being that such effects result from prior learning of specific flavour-taste associations in foods e. Note here also that the concept that there are two senses of smell, orthonasal and retronasal, is also typically confusing, or surprising to the layperson.
That, or so it has been suggested, is why they think of smell referring to orthonasal is not involved in tasting flavours. And this is before we get to the complexity that is introduced by the fact that we use the word taste to talk about aesthetic appreciation here [ 92 ].
Indeed, some scientists believe that there may be 15—20 more basic tastes, such as metallic, fatty acid, and kokumi, that are awaiting their proper recognition [ 15 , 93 ].
As Stuckey [ 15 ], p. And anyone who has tasted a mixture of the basic tastes at a near-threshold level knows how strange and empty an experience it is.
Fincks HT. The gastronomic value of odours. Contemp Rev. Google Scholar. Spence C, Piqueras-Fiszman B. The perfect meal: the multisensory science of food and dining. Oxford, UK: Wiley-Blackwell; Book Google Scholar.
Sivak M. Lyman B. A psychology of food, more than a matter of taste. Mutual action of taste and olfaction. Sens Processes. Eating can be more enjoyable when the other aspects of flavor, such as texture, temperature, and spiciness are emphasized. Texture can be enhanced by adding crunchy foods nuts, croutons, water chestnuts to your meals. Combining cold and hot temperatures in the same dish sour cream on a baked potato , as well as trying hot and spicy foods may help to make food less bland.
Keep in mind that a pleasant atmosphere and attractively prepared meals can also help to make food more enjoyable. We would strongly recommend that you equip your home with smoke detectors. Those individuals potentially exposed to gas leaks should consider purchasing a gas detector. Your gas company should be able to supply you with information regarding gas detectors.
If not, the Taste and Smell Center can be contacted for this information. In order to guard against eating food you suspect may be spoiled, ask someone else to smell it. If that is impossible, pay particular attention to the dates stamped on most perishable foods and do not consume them after that date. UConn Health. However, in some cases after a cold, smell and taste might not return so quickly. According to Dr.
Holbrook, this is thought to be caused by a viral infection that harms the olfactory neurons and diminishes your sense of smell and taste for longer periods of time.
If this occurs, it is important to speak to your doctor and be evaluated by an ear, nose, and throat ENT specialist to determine the possible cause. There are not many treatment options for these patients. But, fortunately, the nerves of your nose are able to regenerate.
Many patients do recover, although it could take several months to years. There is also a newer treatment for smell loss known as odorant training that has seen encouraging results. It calls for patients to smell four odors — rose, eucalyptus, lemon and clove — twice each day. Sometimes, patients believe that they have taste loss, when it is actually a loss of smell. Holbrook noted. It is difficult to have a complete taste loss, so most of these patients notice a decreased or altered sense of taste.
Many describe a metallic taste in their mouths when eating or drinking. This can be a result of many causes, including infection, central brain disorders, nutritional deficits or complications in surgery of the mouth or ear. When there is a loss of taste, it should also be evaluated by an ENT specialist.
If you or a loved one experience persistent loss of smell or taste, Dr. Holbrook recommends seeing a doctor. There could be an underlying cause to be addressed, or — worse — there are dangerous hazards that can accompany these losses, especially for those with a loss of smell i.
Holbrook said. Eric Holbrook, M. Eye and Ear. Search the Mass. Eye and Ear physician directory to find the right ophthalmology eye or otolaryngology ear, nose and throat specialist. Good article.
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