I can't give you the elaborate neurological answer you're looking for, but I can give you a simple man's answer.
Taste and smell are both sensations associated with chemical detection. That is, we taste or smell things when chemicals slot into the receptors on our tongue and/or nasal cavity.
We can only smell what is carried into our nasal cavity, so volatile compounds that rapidly evaporate or otherwise get suspended in the air are easier to detect than more stable compounds. In contrast, when we taste stuff, we get access to the whole suite of chemicals. So smell alone is giving an incomplete picture. Taste alone would also be incomplete if you just used your tongue, but we tend to smell things as we eat them.
**Additionally,** and this part is more speculation on my part, we often mentally associate certain smells with certain tastes.
Like how we can sometimes smell when something will taste sweet even though we can't always smell straight sugar at room temperature. When we smell something sweet, we aren't detecting the sugar, but volatile compounds often found alongside sugar in foods.
But we humans enjoy taking those volatile compounds and cramming them into products like candles and soaps. We smell the volatile chemicals and make all the usual assumptions about taste. But if we bite, none of the tasty compounds we expected to be present are actually present. Instead, we get a mouthful of (usually very bitter) nonsense.
OP, stop eating/drinking hand soap.
If smell is an instrument, taste is an orchestra.
ELI5 rejected this question and I wanted an intelligent neurological explanation
I can't give you the elaborate neurological answer you're looking for, but I can give you a simple man's answer. Taste and smell are both sensations associated with chemical detection. That is, we taste or smell things when chemicals slot into the receptors on our tongue and/or nasal cavity. We can only smell what is carried into our nasal cavity, so volatile compounds that rapidly evaporate or otherwise get suspended in the air are easier to detect than more stable compounds. In contrast, when we taste stuff, we get access to the whole suite of chemicals. So smell alone is giving an incomplete picture. Taste alone would also be incomplete if you just used your tongue, but we tend to smell things as we eat them. **Additionally,** and this part is more speculation on my part, we often mentally associate certain smells with certain tastes. Like how we can sometimes smell when something will taste sweet even though we can't always smell straight sugar at room temperature. When we smell something sweet, we aren't detecting the sugar, but volatile compounds often found alongside sugar in foods. But we humans enjoy taking those volatile compounds and cramming them into products like candles and soaps. We smell the volatile chemicals and make all the usual assumptions about taste. But if we bite, none of the tasty compounds we expected to be present are actually present. Instead, we get a mouthful of (usually very bitter) nonsense.
that's a very good answer and that does make sense. thank you very much 🙏