Salt wins by subtraction. A pinch can make dark chocolate taste sweeter because sodium can suppress bitterness, allowing sweetness already present in the chocolate to become more noticeable without adding a single grain of sugar. The chemistry stays unsweetened. What changes is the balance of sensations, not the amount of sugar listed on the wrapper.
Bitterness is no bystander. Cocoa contains bitter compounds, including the methylxanthines theobromine and caffeine, whose contribution varies with the beans, processing and recipe. Their influence reaches beyond bitterness. Through mixture suppression, one taste can reduce the perceived intensity of another, so bitterness can partly obscure sweetness even when sugar is present. Sodium can weaken that interference. Taste studies show that sodium salts can suppress certain bitter sensations, although the size of the effect depends on the bitter compound and concentration. No universal switch exists. Salt does not simply turn off every bitter taste receptor, and chocolate's fat, aroma and melting behavior also shape the final impression.
Restraint makes the difference. At low levels, salt may shift the balance toward sweetness; at higher levels, its own taste becomes conspicuous and can overwhelm the chocolate instead. A few crystals suffice. Comparing two pieces from the same bar, with only one lightly salted, offers a practical demonstration, though individual sensitivity means the result will not be identical for everyone. Texture can intrude, too. Coarse crystals deliver brief bursts of saltiness, whereas dissolved salt spreads more evenly, changing how each bite unfolds across the tongue. The sugar remains still. Around it, the shadows move.