I hope I'm not using the wrong word here, since I know the "acidic" quality to a food does not change by adding sugar (same amount of free hydrogen ions).
But it's known that adding sweetness reduces sourness (the perception of acidity). For example a lemon and Coke both have a pH of around 2.5, but the Coke tastes far less sour because of the added sweetness.
My question is... why is this the case? Why does adding sugar reduce this perception? In all these websites it explains how this-paired-with-that creates such and such effect, and while I am sure it suffices to just "memorize that," I want to understand it better.
Is it known what's going on, on a molecular level, or a physical level, as to why introducing sweetness reduces the perception of acidity specifically?