Tongue Tied Taste

“Sour, sweet, bitter, pungent, all must be tasted.”  – Chinese proverb

Famous four or five?

Surely there was more to my richly flavoured bowl of noodles last night than the four basic tastes which most of us recognise?  There was a rich savoury sensation on my tongue which I find difficult to describe, although it’s well understood in Asia.

Along with sweet, sour, salty and bitter, umami is now recognised as the fifth basic taste.  Umami means “good flavour” or “good taste” in Japan (where it was discovered), and along with the other four, is sensed via taste receptors on our tongue. Westerners prefer to call it the “savoury” or “meaty” taste, and it is present in meat, cheese, mushrooms and of course soy sauce.  Detection of all five tastes is important in regulating consumption, performing a vital role in helping us decide what can safely be ingested and what we should spit out.  [As an interesting aside, the tongue is also the most flexible muscle we possess!]

Although some psychophysicists have suggested that there may be others (for example, fatty acid and metallic tastes), five are commonly accepted.  The roles of these five are summarised as below:

Sweetness is often linked to energy-rich high calorie foods which are pleasurable and, most importantly, nourishing.

Sourness is often a danger sign for food which is unripe or “off” and unsafe to consume.

Saltiness is present in most chemical salts, including sodium chloride, which have important functions in regulating our body.

Bitterness is often linked to natural toxins and is a signal for poisons which should be avoided.

Umami is the savoury taste of protein rich foods.

The surface of the tongue

These tastes can be perceived all across our tongues, although it was long believed that certain areas of the tongue were specific to each taste.  Sourness and bitterness are aversive, and as we grow older many of us will learn to like them and overcome our natural aversion (do you remember your first beer or fresh lemon juice?).  [Spiciness from capsaicin is also aversive and has to be learned to be liked, although it is technically due to burning sensations rather than taste.]  Herbivores (for example, cows) have far fewer bitter taste receptors than omnivores (like man), giving them far greater potential variety in their diet as they are less selective, although they have to have far bigger livers to manage the toxins in their bodies!

Taste is not alone

In The Chemical Sense I wrote about how what we “taste” comes from more than just our basic taste, but is a rich combination of the perceptions of our tongue along with the other senses.  Smell is the most critical accounting, by some estimates, for around 80% of the sensation of taste when we eat and drink, primarily through the flavour volatiles which go the back of our nose while we chew food.  Other senses play a role too: temperature and pain affect taste perception greatly: it seems that pain (capsaicin for instance) works by initially reducing taste sensations and then enhancing them as the pain moderates.  This is in addition to the release of endorphins which give the chilli buzz!

Sound is also a key player in the perception of texture.  The loudness and timbre (pitch) of sound we experience both in the air and through vibrations in our jawbone, change our perception of the texture of foods like crisps.

We taste what we see

The most important sense in defining our perceptions of taste is vision.  Because of it’s dominance in our sensory world (which I will write about in future), vision tends to override smell and taste where there is conflicting information.  Hence, the ability of experimenters to trick us by changing the colour of a fruit flavoured drink (if it’s green, then it must be lime right?), or wine (if it’s red, then surely it’s more full bodied).

Wine seems to be popular in testing the roles and abilities of our senses, and was one of the first industries to adopt more rigorous techniques from sensory science to understand and improve product perceptions.  Another experiment you may have read about elsewhere involves the role of expectations in altering perceptions of products.  Wine priced at $ 115 tastes a whole lot better than wine priced at $ 15 (even if it’s actually the same), and in another interesting twist on this, diners given a free glass of California red wine, finished much more of their food than diners given a free glass of North Dakota red wine.

We taste what we understand

The wine industry (along with coffee, perfumes and others) employs “experts”.  We all accept that some people have more taste ability than others, but a large part of the ability of wine tasters comes from their rich conceptual understanding of the language and meaning of the elements of any wine they taste.  This conceptual understanding comes from their experience (another case of 10,000 hours of practice leading to expertise perhaps?).  Brain imaging of wine tasters shows much greater brain activity in three areas and stages: the initial sensory impression (which creates a much stronger “representation” in experts), analytic (left brain) processing of the representation and in the final stage much greater activity in the memory and language areas of the brain (conceptualisation).

This ability is because experts can describe what they taste without interfering with their ability to perceive the sensation.  Several experiments have shown that non-expert tasters often have the same ability to perceive differences between wines, but lack the ability to conceptualise the differences. More importantly, asking non-experts to describe a wine, reduces their ability to recognise a wine (even if just tasted).  So if one group of tasters are asked to recognise a wine without describing their perceptions, while another group of tasters are asked to describe the wine first, then the first group will have much higher accuracy in recognising what they are tasting.

This is known as verbal overshadowing, which has been well documented in criminology (and also in perception of music, visual images, colours, etc).  Verbal overshadowing happens when someone’s ability to perceive is greater than their verbal skills.  Asking for a description is a distraction from non-verbal information (the brain has to focus on processing of language and forgets about other tasks).  For example, in scene of crime studies, the ability to recognise facial characteristics is reduced when witnesses are asked to describe the perpetrator before identifying them.  This is because our brain’s ability to recognise faces is much stronger than our ability to describe faces.  It may also be related to the distortion which can happen when our mind reconstructs events from memory.

Overshadowing research?

We all have much greater ability to experience the rich tastes of food than we do to describe those experiences (even for experts or “supertasters” who are less than 20% of the population).  Forget about the 20,000 odours that our nose can detect, ability to describe even the basic tastes is extremely limited.  In work I have conducted in the UK, only 90% of consumers accurately describe a sugar solution as “sweet”, with 67% describing sourness, 53% saltiness and 18% bitterness!

How many characteristics are typically included in a product test questionnaire?  I don’t believe that the majority of us can adequately answer such questions.  More importantly, focusing on the task of description may take away from the more important job of experiencing the product.

Innovation is about creating great product experiences for consumers.  Market research should focus on measuring the consumer experience, and leave description to the experts!


A Natural History of the Senses by Diane Ackerman (1991)

The Brain Book by Rita Carter (2009)

See What I’m Saying: The Extraordinary Powers of our Five Senses by Lawrence D. Rosenblum (2010)

The Buying Brain: Secrets for Selling to the Subconscious Mind by A.K. Pradeep (2010)

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