How does the sense of taste work

The tongue map, also known as the taste map, is a diagram that shows the different areas of the tongue that are sensitive to different basic tastes. It is taught in schools and therefore believed to be true. However, the tongue map is a simplification that does not accurately reflect the way taste buds are distributed on the tongue. 

The tongue map was originally based on a study that was published in 1901 by a German scientist named David P. Hanig. Hanig conducted a series of experiments in which he applied different tastes to different areas of the tongue and then asked subjects to identify the tastes. He found that certain tastes were more easily identified when applied to certain areas of the tongue, and he proposed that the tongue was divided into separate regions that were each sensitive to a specific taste. 

However, Hanig was careful to note that every sensation could also be tasted throughout the tongue and that the areas identified offered very little variation.
So where did the confusion come from? The taste map as we have been taught was first sketched and published by Edwin G. Boring in 1942.

Edwin Boring misinterpreted the studies from Hanig by simplifying and overgeneralizing his finding. Indeed, Hanig’s studies showed that different areas of the tongue were more sensitive to certain tastes, however, he also pointed out that all areas of the tongue could detect all tastes. Boring misunderstood this and claimed that different parts of the tongue were solely responsible for specific tastes, which led to the creation of the tongue map myth. 

Hanig initially presented his information in a graph that was rather confusing to other researchers at the time, because it appeared to outline where tastes were picked up on the tongue – he was actually trying to show those areas of the tongue were SLIGHTLY more sensitive to a certain basic taste than others, and not that they were only sensed in these areas, which is a pretty big difference. 

This misrepresented information was then picked up by Boring 40 years later when he illustrated the graphic as a map of the tongue. 

Boring’s map outlined areas for four tastes: sweet (at the tip of the tongue), salty and sour (in the middle), and bitter at the very back. At this point, please note that both Hanig and Boring didn’t account for Umami taste, as scientists only recognised this at some point in the 1990s. 

However, subsequent research has shown that the tongue is not divided into separate regions that are each sensitive to a specific taste. Instead, the taste buds are distributed throughout the entire surface of the tongue, and they are able to detect all five primary tastes (sour, sweet, salty, umami, bitter). 

While it is true that some areas of the tongue may be more sensitive than others, the sensitivity of the taste buds can vary from person to person and can depend on a variety of factors, such as age, diet, and overall health. 

Let’s see how this works. You can read a quick introduction on the sense of taste in post #1

Taste buds are specialized sensory cells that are located on the surface of the tongue and other areas of the mouth. They are responsible for detecting the five basic tastes: sour, sweet, salty, umami, and bitter. More recent studies also claim that metallic and fat are basic tastes too, but we will explore this another time. 

When we eat or drink, molecules of the substances we consume dissolve in saliva and come in contact with taste buds. The taste buds contain specialized receptors that bind to specific molecules, causing a chemical reaction. This reaction sends a signal to the brain, which interprets the signal as a particular taste. 

The brain is able to distinguish between the different tastes because each type of molecule activates a unique combination of receptors. For example, the molecule that gives sugar its sweet taste activates a different combination of receptors than the molecule that gives lemons its sour taste. The brain is able to recognize and differentiate between these patterns of receptor activation, allowing us to perceive the different basic tastes. And each type of receptor is evenly distributed on the mouth, therefore allowing us to sense each basic taste on all regions of the tongue and palate. 

The sensitivity of the taste buds and the individual’s ability to perceive different tastes can vary. Some people may have a more sensitive sense of taste and be able to detect a wider range of tastes, while others may have a less sensitive sense of taste, a may be less able to distinguish between tastes. 

The order in which we perceive basic tastes is an interesting thing to point out. We already mentioned that saliva plays an important role in gustation. Saliva contains enzymes that help break down the chemical components of food and drinks, allowing our taste buds to detect them. 

The ability of saliva to break down each basic taste varies depending on the specific taste. For example, enzymes in saliva called amylases are responsible for breaking down carbohydrates and sugars, which contribute to detecting sweetness. Saliva also helps to dissolve and distribute salt ions, contributing to our ability to detect salty taste. 

Overall, our body needs sugar and salt in order to survive, and these basic tastes will be normally among the first to be perceived during gustation, as our brain is always on a ‘hunt’ for these vital compounds.  

In contrast, bitter compounds can be more difficult for saliva to break down and may require more time and exposure to fully detect. Therefore, when tasting something, the bitterness may be perceived after some other basic tastes (‘bitter aftertaste’ anyone?). 

In general, this ‘taste sequence’ is not a hard and fast rule, and the order in which we perceive the basic tastes can vary, depending on their concentration and other factors. 

However, next time you enjoy a Negroni, try to pay attention to the very first basic taste that you perceive, and at which point the bitterness develops on your palate. 

Heat and Cold, are those basic tastes? 

The spiciness of chilli pepper and the cooling feeling of mint chewing gum, are not considered basic tastes. These sensations are actually related to the trigeminal nerve, which is responsible for detecting physical sensations such as temperature, pressure, and pain. The sensation of heat comes from the activation of this nerve by capsaicin, the compound that makes chilli peppers spicy. The sensation of cold, on the other hand, comes from the activation of the same nerve by menthol, the compound that makes minty flavours cooling. 

While these sensations may not be basic tastes, they can still play an important role in the overall sensory experience of food and drink. For example, a dish's spiciness can add complexity and depth to its flavour profile, while the coolness of a mint can provide a refreshing sensation. 

Can you ‘smell’ sweetness? 

No, and we already covered this in posts 1 and 2. However, there is a connection between certain scents and basic tastes. When we smell certain substances, our brain often associates them with particular tastes. This is because both taste and smell rely on similar types of sensory receptors in our bodies. 

For example, the scent of vanilla (but also cinnamon, fennel seeds, fruit, etc.) is often associated with sweetness, while the smell of vinegar, citrus, fermented foods, and so on, is often associated with sourness. This connection between scents and basic tastes is thought to be an evolutionary adaptation that helps us identify and evaluate the nutritional value of foods. In the wild, our ancestors would have needed to quickly identify which foods were safe to eat and which were not. By associating certain scents with basic tastes, our brain can quickly determine whether a food is likely to be nutritious or not.

You might have heard of Supertasters… 

Supertasters are individuals who possess an enhanced ability to perceive taste due to a heightened number of taste buds and taste receptors on their tongues. This genetic variation in taste sensitivity makes them highly sensitive to the basic tastes of sweet, sour, bitter, and salty, as well as to more subtle flavours. Supertasters often experience intense sensations and may find certain foods, especially bitter ones like dark leafy greens or coffee, overwhelming or unpalatable. Conversely, they may also have a strong preference for sweet and (especially) salty foods. While being a supertaster might sound like an incredible plus for individuals working in the food and flavour industry, it can actually present several challenges and be a disadvantage. But we will talk about this another time.