A pungent, tangy taste in coffee, registered on the tip and sides of the tongue, is called acidity. The degree of acidity is an important aspect of coffee flavor, not as measured chemically, but as experienced by drinking the coffee. A robusta coffee grown at a low altitude may have a pale, bland flavor; an arabica coffee grown above 4500 feet at lower temperatures will have a bright, refreshing acidity. The acids emerge as coffee is roasted and light roasts enhance them. Dark roasts diminish acid qualities and emphasize sweetness.