Artists, held in high regard in Mayan society, wrote hieroglyphs and made illustrations in ancient folded books called codices. There is a clear link between the style of the art produced in these codices, and other types of art, such as painted ceramics. Mayan codex-style art is filled with expressive characters and bold colors. These paintings, whether in a book or on a vessel, have text which helps to explain the meaning of the images. These hieroglyphic inscriptions sometimes represent images (and are therefore pictographic) and sometimes represent sounds. A system of dots and bars was used to mark time. Scholars think it was common for the writing and the illustrations to have been completed by the same person, and refer to them as artist-scribes.