Lip reading is a communications technique allowing a person to understand speech through visual cues alone. Vocal speech involves certain specific mouth shapes for each sound; a lip reader learns to recognize and interpret these shapes. It is mainly practiced by the deaf and hard of hearing, although anyone can learn and practice the technique. The phrase lip reading is a misnomer, as practitioners also gain clues from watching the teeth and the tongue, as well as facial cues and body language. For this reason, it is sometimes called speech reading instead.
Deaf and hard-of-hearing people have developed numerous techniques to understand and communicate with members of the hearing world. The most famous is sign language, which is actually a family of languages communicated silently through hand and facial gestures. Sign language has multiple variations, including versions used by military and law enforcement for silent communication, and a touch version used to communicate with those who are both deaf and blind. Understanding sign language involves not just gestures, but facial expressions, body language, and the context and intent of the person communicating. Similarly, lip reading is only part of a process allowing communication without the use of sound.
Lip reading is not a perfect form of communication. Reading someone’s lips requires intense concentration, and even the most practiced of lip readers can catch only 30 to 40 percent of a speaker’s meaning by watching lip motions. Many sounds are formed in the throat or the back of the mouth, where they cannot be read, and the visual indicators of many sounds appear similar. It is also useless if a person’s mouth is obscured or facing away from the lip reader. This is why sign language and writing are more convenient and complete methods of communication for many deaf and hard-of-hearing people.
In deaf communication, lip reading is most effectively taught to those who had hearing at one time. People who were born deaf may find it difficult or impossible to understand and process the visual cues of spoken speech. Hearing people may learn the technique for reasons that have nothing to do with hearing loss. For example, law enforcement personnel may learn it as a surveillance technique. It can also be useful for those studying speech therapy and related fields.
The expression read my lips is often used by speakers to emphasize the importance or veracity of what they are saying. President George H. W. Bush famously used the phrase “Read my lips: no new taxes,” during the 1988 U.S. presidential election. The line returned to haunt him in the 1992 election, as the new taxes he had imposed during his term in office made him seem untrustworthy. In the 1968 film 2001: A Space Odyssey, the sinister computer HAL 9000 uses lip reading to discover its human companions’ plans to disconnect it. Ironically, in the 21st century, software designers are teaching computers to read lips as a means to improve voice-recognition software.