Infants can discriminate differences in taste shortly after birth. They prefer sweet-tasting liquids to those that are salty bitter, sour or bland The characteristic response of the newborn to a sweet liquid is a relaxed expression resembling a slight smile, sometimes accompanied by lip licking. A sour solution produces pursed lips and a wrinkled nose. In response to a bitter solution, the baby will open its mouth with the corners turned down and stick out its tongue in what appears to be an expression of disgust.