In typography, all caps (short for "all capitals") refers to text or a font in which all letters are capital letters, for example: "THIS TEXT IS IN ALL CAPS". All caps may be used for emphasis (for a word or phrase). They are commonly seen in legal documents, the titles on book covers, in advertisements and in newspaper headlines. Short strings of words in capital letters appear bolder and "louder" than mixed case, and this is sometimes referred to as "screaming" or "shouting". All caps can also be used to indicate that a given word is an acronym. Studies have been conducted on the readability and legibility of all caps text. Scientific testing from the 20th century onward has generally indicated that all caps text is less legible and readable than lower-case text. In addition, switching to all caps may make text appear hectoring and obnoxious for cultural reasons, since all-capitals is often used in transcribed speech to indicate that the speaker is shouting. All-caps text is common in comic books, as well as on older teleprinter and radio transmission systems, which often do not indicate letter case at all. In professional documents, a commonly preferred alternative to all caps text is the use of small caps to emphasise key names or acronyms (for example, ), or the use of italics or (more rarely) bold. In addition, if all caps must be used it is customary to slightly widen the spacing between the letters, by around 10 per cent of the point height. This practice is known as tracking or letterspacing. Some digital fonts contain alternative spacing metrics for this purpose. Association with shouting or yelling Messages typed completely in capital letters are often equated on social media to shouting and other impolite or argumentative behaviors. This became a mainstream interpretation with the advent of networked computers, from the 1980s onward. However, a similar interpretation was already evidenced by written sources that predated the computing era, in some cases by at least a century, and the textual display of shouting or emphasis was still not a settled matter by 1984. The following sources may be relevant to the history of all caps: The 17 April 1856 edition of the Yorkville Enquirer (South Carolina) uses the expression "This time he shouted it out in capital letters." The 1880 book The Standard speaker and elocutionist has a section titled "SHOUTING STYLE", which