Final answer:
An apple, onion, and potato taste the same with a plugged nose because the sense of smell, which is a significant contributor to taste perception, is impaired. Olfactory receptors in the nose are unable to detect odors, leading to a diminished ability to discern distinctive flavors.
Step-by-step explanation:
The question at hand is concerned with why an apple, onion, and potato all taste the same when your nose is plugged. This phenomenon is related to the role that the sense of smell plays in our perception of taste. Olfactory receptors in our nose detect odors in the air, which contribute significantly to the taste experience. When we have a stuffy nose, or if we plug our nose, our ability to smell is compromised. This affects our taste perception because the molecules from the food cannot reach the odor receptors in the nasal passages. Therefore, without the contribution of smell, foods can taste less distinctive or similar to one another.
Similarly, food seems to have less taste when we are congested. A stuffy nose from a cold, for example, can block the passage of odor molecules to the olfactory receptors, resulting in a decreased ability to taste flavors fully. This is why bland foods may taste the same when our sense of smell is impaired.
Moreover, it's not just common observation, but a knowledge question that without the sense of smell, the vast array of flavors we can experience diminishes considerably. So, while the basic tastes such as sweet, salty, sour, bitter, and umami can be detected by the tongue's taste buds, the nuanced flavors are actually discerned through the sense of smell.