Speech Disorders: Overview

A speech disorder is a condition that interferes with a person's ability to speak clearly and be understood. It may be caused by congenital problems, developmental delays, hearing problems, accidents, strokes, or defects in any of the organs or muscles involved in producing speech or in any of the areas of the brain that control speech.

How Does Speech Develop?

Speech and language develop most intensively during the first three years of life. When babies are born, they can make sounds by pushing air outward from the lungs and through the vocal cords in the throat. The air causes the vocal cords located in the larynx (LAR-inks), or voice box, to vibrate and thereby create sound.

Many people who are deaf and/or unable to speak learn to communicate through manual communication or signed language.

Many people who are deaf and/or unable to speak learn to communicate through manual communication or signed language.

During the preschool years, children increase their mastery of speech sounds, word and sentence formation, word and sentence understanding, tone and rhythm of speech, and effective use of language.


Spoken language is not the only way that people can communicate. Many people who are deaf and/or unable to speak learn to communicate through manual communication, commonly called sign language. In the early 2000s, three signed languages were used in the United States: American Sign Language (ASL), Signed Exact English, and Cued Speech. These sign languages have a European ancestry that goes back several centuries.

In the early 1700s, a Spanish priest named Juan Pablo Bonet (1573–1633) published a book on the use of sign language to teach deaf people to speak. Bonet's work in Spain was followed in France by another priest, Charles-Michel de l'Épée (1712–1789), who learned what became known as French Sign Language from a chance encounter with two deaf sisters who had improvised a manual sign language. While l'Épée did not invent French Sign Language, he started the world's first free school for the deaf so that the sisters’ sign language could be taught to others. In 1816, Thomas Gallaudet (1787–1851) brought French Sign Language to the United States. French Sign Language was modified to incorporate English terms while maintaining French sentence structure, to form what later was called American Sign Language (ASL). Gallaudet University in Washington, D.C., is named for Thomas Gallaudet.

Signed Exact English, also known as Signing Exact English or SEEII, was developed in 1972 by educators in California who worked with children with hearing loss and deafness. This language uses the same alphabet as American Sign Language but modifies the hand signs and places them into English sentence structure.

Cued Speech, developed in 1966 by the American scientist R. Orin Cornett (1913–2002), uses hand signs to represent sounds rather than letters or concepts. It is used in conjunction with mouthing word cues, such as the most prominent vowel in each word. Cued Speech is not limited to English; it was adapted for use by French speakers in 1977, and has been adapted to 60 different languages around the world as of 2016.

How Common Are Speech Disorders?

Stroke, trauma, or infection may be the root cause of these disruptions. Severe intellectual disability often has a negative impact on speech development. In some cases, physical abnormalities play a role in speech disorders. For example, cleft palate * , cleft lip * , hearing problems, and damage to the larynx all can interfere with speech.

Speech disorders are fairly common in children; according to the National Institute on Deafness and Other Communication Disorders, about 5 percent of first-graders in the United States have noticeable speech disorders. Many children show delays in developing speech, a condition that is frequently outgrown. Often the cause of a child's speech disorder is never known.


What do singers Carly Simon and Mel Tillis, television journalist John Stossel, and actors James Earl Jones, Marilyn Monroe, and Bruce Willis have in common? All had the problem of stuttering. Their public successes point to one of the unique features of stuttering—although it is a problem in everyday conversation, it often disappears when someone is singing or delivering memorized lines. Furthermore, people who stutter often can learn strategies for overcoming the problem as they grow older.

James Earl Jones

In his autobiography, the actor James Earl Jones describes how he overcame his stuttering problem by reading Shakespeare aloud to himself, and then reading to audiences, debating, and acting. Jones provided the voices for Darth Vader in Star Wars and King Mufasa in the animated Lion King. He has acted on stage and in numerous films.

John Stossel

As a reporter for the television news magazine 20/20, John Stossel depends on his voice to make a living. He stuttered as a child and worked hard to hide the condition. Stossel started his career in news as a researcher, but eventually he was asked to go on the air. He considered quitting when he found himself stumbling over certain words, but he got help overcoming his stuttering through speech therapy at the Hollins College Research Institute in Roanoke, Virginia. Stossel later became a spokesman for the National Stuttering Association.

When adults develop a speech disorder after years of speaking normally, it usually is easier to locate the cause. For instance, a stroke * , head injury, brain tumor, or dementia * may involve damage to the areas of the brain that affect speech or speech understanding. In other cases, an accident, a surgical procedure, or a viral infection can cause damage to the nerves that control the functions of the larynx.

What Are the Different Types of Speech Disorders?

There are two major types of speech disorders: those caused by abnormalities in the muscles and other structures of the mouth and throat, and those caused by disorders of the central nervous system. The first type of speech disorders are called phonological or articulatory disorders, and the second type are called brain disorders.

Phonological (Articulatory) Disorders

Phonological, or articulatory (ar-TIK-yoo-la-tor-ee), disorders interfere with the process whereby the muscles of the mouth, tongue, jaw, throat, and diaphragm * work together to produce clear, understandable sounds. These problems typically begin in childhood and can persist into adulthood. They also may be called fluency disorders.

It is normal for children to have problems with articulation as they are learning to speak. For instance, many children between two and three years of age are unable to pronounce the sound “th.” Other children in this age group stutter, which means that they repeat sounds occasionally or hesitate between words. Most children outgrow such problems rather quickly. If problems persist, however, they are considered speech disorders.


A lisp is a relatively common speech disorder in which a person has trouble pronouncing the sounds of the letters s and z. One of the best-known lispers is Sylvester the Cat, featured in the Tweety Bird cartoons, whose favorite exclamation is “thuffering thuccotash!” (suffering succotash).

Lisping can happen for a variety of reasons: an abnormal number or position of teeth; unconscious imitation of other lispers; such defects in the structure of the mouth as a cleft palate; or hearing loss. Usually lisps can be corrected by working with a speech-language therapist who coaches the person with the lisp on how to make the sound correctly.


People who stutter may repeat a speech sound over and over (st-st-stuttering), or they may hold a sound longer than normal (sssssstuttering). In some cases, they may have trouble starting a word, leading to abnormal stops in their speech (no sound). Stuttering often begins in early childhood and may persist into adulthood. People who stutter repeat certain speech sounds, prolong certain sounds, or hesitate before and during speaking. Stuttering often is referred to as a fluency disorder because it disrupts the smooth flow of speech. More than three million Americans stutter, and most began stuttering between the ages of two and seven. Boys are three times more likely to stutter than girls.

Being a Good Listener

People talking to others who stutter should do the following:

Stuttering can have social and emotional consequences. People who stutter may be self-conscious about their speech. Some show signs of tension, such as twitching, unusual facial expressions, or eye blinks when trying to get out their words. Experts are not sure what causes stuttering, although some studies show that stuttering has a tendency to run in families, suggesting that it may have a genetic component.

Other cases of stuttering may be neurogenic (NOOR-o-JEN-ik), meaning that that they are caused by signal problems between the brain and the nerves or muscles that control speech. Stuttering also may result from emotional trauma, stress, or other psychological causes.

Researchers have found that stuttering affects males about three times more often than females; the reason for this difference is not known as of 2016. Certain situations, such as speaking before a group of people or talking on the telephone, may make stuttering more severe for some, whereas singing or speaking alone often improve fluency.

Most children go through a stage of choppy speech when they are first learning to talk. In addition, teenagers and adults often add extra sounds (for example, “uh” and “um”) to their speech, and they occasionally repeat sounds. These speech interruptions are perfectly normal. Such problems are considered a disorder only when they last past the age when most children outgrow them and when they interfere with communicating clearly. Treating stuttering even in young children may help prevent a lifelong problem. Treatment may be considered for children who stutter longer than six months or for those who seem to struggle when they speak. Sometimes, however, no treatment is the best treatment, especially in the case of children whose stuttering worsens when attention is focused on the problem.

It is estimated that less than 1 percent of American adults stutter. Many people have overcome stuttering and gone on to achieve success in careers that require public speaking, acting, and singing. A well-known 2010 movie, The King's Speech, highlights the struggle of King George VI (1895–1952), the father of Queen Elizabeth II, to overcome the severe stammer that had troubled him since childhood. The movie details the king's long-term but successful work in the late 1920s and 1930s with an Australian speech therapist named Lionel Logue. The film was honored by the Royal College of Speech and Language Therapists for offering encouragement to other people who struggle with speech disorders.

Brain Disorders

Speech disorders in adults usually are the result of damage to the portions of the brain that control language. Damage may be caused by head injury, brain tumor, or stroke. Adults who have aphasia (a-FAY-zha) have trouble speaking and difficulty understanding what others are saying. Dysphasia (dis-FAY-zha) is a condition that causes similar but less severe challenges in speaking and understanding. The symptoms of aphasia and dysphasia depend on which area of the brain is affected: Broca's area or Wernicke's area.

Location of Broca's area and Wernicke's area of the brain.

Location of Broca's area and Wernicke's area of the brain.
IIllustration by Frank Forney. © 2016 Cengage Learning®.
Broca's aphasia

Broca's aphasia results from damage to the area in the frontal lobe of the brain that coordinates the muscles of the lips, tongue, jaw, and vocal cords that produce understandable speech. It is named for Pierre Paul Broca (1824–1880), the French physician who first identified its role in speech production. People with damage to Broca's area frequently speak in short, meaningful phrases that are produced with great effort, omitting small words such as “is,” “and,” and “the.” People with Broca's aphasia often are aware of their speech difficulties and may become frustrated by their speech problems.

Wernicke's aphasia

Wernicke's aphasia results from damage to the area of the brain responsible for understanding speech, located in most people in the left cerebral hemisphere. It is named for Karl Wernicke (1848–1905), a German psychiatrist who was inspired to investigate speech disorders after reading about Broca's work. People afHicted with this form of aphasia have trouble understanding others and often are unaware of their own problems. They may speak in long rambling sentences that have no meaning, often adding unnecessary words. They may even create nonsense words.

Global aphasia

Global aphasia results from damage to large portions of the language areas of the brain. Individuals with global aphasia have severe communication difficulties and may be extremely limited in their ability to either speak or comprehend language.

How Do Doctors Diagnose and Treat Speech Disorders?


Many adults recognize when they develop a speech difficulty and seek help from doctors and trained speech-language therapists. Parents of children with speech disorders often are the first to call the condition to the attention of healthcare providers.

* may also be involved in the evaluation process.

Stuttering usually is diagnosed by a speech-language pathologist (pa-THAH-lo-jist). The speech pathologist will ask questions about the problem, such as when it first started and when it is most and least noticeable. The speech pathologist will also test the person's speech and language abilities.

Treatment of Aphasia

People with aphasia often benefit from speech-language therapy, which focuses on helping people make the most of their abilities and learn other methods of communicating. Supplemental methods of communication that assist an individual in speaking are called augmentative communication devices (ACDs). Available ACDs include portable communication computers, personalized language boards, and picture exchange programs. As technology continues to improve and become more easily portable, communication possibilities for aphasic and dysphasic adults continue to expand.

Treatment of Stuttering

There are several treatments that may improve stuttering, although none is an instant cure. With young children, the focus is often on teaching parents how to help the child at home. Parents typically are told to have a relaxed attitude and give their children plenty of opportunities to speak. They may be advised not to criticize their children's speech. Instead, they are encouraged to be good role models, speaking in a slow, relaxed manner themselves and listening patiently when their children talk.

Speech therapy can help older children, teenagers, and adults relearn how to speak or unlearn faulty ways of speaking. Some people who stutter have fears related to the disorder, such as a fear of speaking in public. Such problems caused by the stuttering can be helped with psychotherapy (SIGH-ko-THER-a-pea), in which people talk about their feelings, beliefs, and experiences with a mental health professional who can help them work out issues that play a part in their speech problems.

See also Alzheimer's Disease • Birth Defects: Overview • Brain Injuries • Brain Tumor • Cleft Palate • Deafness and Hearing Loss • Infection • Intellectual Disability • Laryngitis • Stroke • Trauma • Tumor • Viral Infections


Books and Articles

Bowen, Caroline. Children's Speech Sound Disorders, 2nd ed. Hoboken, NJ: Wiley-Blackwell, 2014.

Leonard, Laurence B. Children with Specific Language Impairment, 2nd ed. Cambridge, MA: Bradford, 2014.

Preston, Katherine. Out With It: How Stuttering Helped Me Find My Voice. New York: Atria, 2014.


American Speech-Language-Hearing Association. “Speech and Language Disorders and Diseases.” http://www.asha.org/public/speech/disorders/ (accessed July 11, 2016).

MedlinePlus. “Speech Disorders – Children.” U.S. National Library of Medicine, National Institutes of Health. https://www.nlm.nih.gov/medlineplus/ency/article/001430.htm (accessed July 11, 2016).

National Institute on Deafness and Other Communication Disorders. “Stuttering.” https://www.nidcd.nih.gov/health/stuttering (accessed July 11, 2016).


American Speech-Language-Hearing Association. 2200 Research Blvd., Rockville, MD 20850-3289. Toll-free: 800-638-8255. Website: http://www.asha.org (accessed July 11, 2016).

National Aphasia Association. PO Box 87, Scarsdale, NY 10583. Website: http://www.aphasia.org (accessed July 11, 2016).

National Stuttering Association. 119 West Fortieth St., 14th Fl., New York, NY 10018. Toll-free: 800-937-8888. Website: http://www.westutter.org (accessed July 11, 2016).

Stuttering Foundation of America. PO Box 11749, Memphis, TN 38111-0749. Toll-free: 800-992-9392. Website: http://www.stutteringhelp.org (accessed July 11, 2016).

* cleft palate is a gap or split in the roof of the mouth (the palate). It is a type of birth defect resulting from the tissues of the face not joining together properly during pregnancy.

* cleft lip is a gap or split in the upper lip. It occurs when the lip of a fetus does not develop properly during the first months of pregnancy.

* stroke is a brain-damaging event usually caused by interference with blood flow to the brain. A stroke may occur when a blood vessel supplying the brain becomes clogged or bursts, depriving brain tissue of oxygen. As a result, nerve cells in the affected area of the brain and the specific body parts they control do not function properly.

* dementia (dih-MEN-sha) is a loss of mental abilities, including memory, understanding, and judgment.

* diaphragm (DY-a-fram) is the muscle that separates the chest and abdominal cavities. It is the chief muscle used in breathing

* neurologist (new-RHAL-eh-jist) is a physician who specializes in diagnosing and treating diseases of the nervous system.

  This information is not a tool for self-diagnosis or a substitute for professional care.