The x-height of a typeface refers to the height of the lower-case x in that typeface. Typefaces with a very large x-height typically have shorter ascenders and descenders and thus less white space between lines of type. Increased leading can assist with readability of these typefaces as it allows for clearer identification of those ascenders and descenders. In typefaces with small x-heights, the ascenders and descenders often become more visually noticeable. It is for this reason that serif typefaces are typically used in longer texts, e.g. novels, as our eyes—and brain—seek out identifiable parts of letters to understand them, rather than taking in every aspect of every character.