applications for the busy human.
Olfactory hallucinations, â smelling things that arenât there, also exist, and can be worryingly common. People often report the phantom smell of burningâtoast, rubber, hair or just a general âscorchedâ smell. Itâs common enough for there to be numerous websites dedicated to it. Itâs often linked to neurological phenomena, such as epilepsy, tumors or strokes, things that could end up causing unexpected activity in the olfactory bulb or elsewhere in the smell-processing system, and be interpreted as a burning sensation. Thatâs another useful distinction: illusions occur when the sensory system gets something wrong, has been fooled. Hallucinations are more typically an actual malfunction, where somethingâs actually awry in the brainâs workings.
Smell doesnât always operate alone. Itâs often classed as a âchemicalâ sense, because it detects and is triggered byspecific chemicals. The chemical sense is taste. Taste and smell are often used in conjunction; most of what we eat has a distinct smell. Thereâs also a similar mechanism as receptors in the tongue and other areas of the mouth respond to specific chemicals, usually molecules soluble in water (well, saliva). These receptors are gathered in taste buds, which cover the tongue. Itâs generally accepted that there are five types of taste bud: salt, sweet, bitter, sour and umami. The last responds to monosodium glutamate, essentially the âmeatâ taste. There are actually several more âtypesâ of taste, such as astringency (for instance from cranberries), pungency (ginger) and metallic (what you get from . . . metal).
Smell is underrated, but taste, by contrast, is a bit rubbish. It is the weakest of our main senses; many studies show taste perception to be largely influenced by other factors. For example, you may be familiar with the practice of wine tasting, where a connoisseur will take a sip of wine and declare that it is a fifty-four-year-old Shiraz from the vineyards of southwest France, with hints of oak, nutmeg, orange and pork (just guessing here) and that the grapes were crushed by a twenty-eight-year-old named Jacques with a verruca on his left heel.
All very impressive and refined, but many studies have revealed that such a precise palate is more to do with the mind than the tongue. Professional wine tasters are typically very inconsistent with their judgements; one professional taster might declare that a certain wine is the greatest ever, while another with identical experience declares itâs basically pond water. 3 Surely a good wine will be recognized by everyone? Such is the unreliability of taste that no, it wonât. Wine tasters have also been given several samples of wine to taste and been unable to determine which is a celebrated vintageand which is mass-produced cheap slop. Even worse are tests that show wine tasters, given samples of red wine to evaluate, are apparently unable to recognize that theyâre drinking white wine with food dye in it. So clearly, our sense of taste is no good when it comes to accuracy or precision.
For the record, scientists donât have some sort of bizarre grudge against wine tasters, itâs just that there arenât many professions that rely on a well-developed sense of taste to such an extent. And itâs not that theyâre lying; they are almost certainly experiencing the tastes they claim to, but these are mostly the results of expectation, experience and the brain having to get creative, not the actual taste buds. Wine tasters may still object to this constant undermining of their discipline by neuroscientists.
The fact is that tasting something is, in many cases, something of a multisensory experience. People with nasty colds or other nose-clogging maladies often complain about being unable to taste food. Such is the interaction of senses determining taste that they
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