Speech Disorders

A speech disorder is a condition that interferes with a person's ability to speak clearly and understandably. It may be caused by 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.


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American Sign Language



Augmentative communication devices

Broca's area

Communication disorders



Wernicke's area

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 out of the lungs and through the vocal cords in the throat. The air vibrates these vocal cords, located in the larynx (LAR-inks) or voice box, creating sound.

Newborns learn that a cry will bring food, comfort, and companion-ship, and they begin to recognize certain sounds. As the jaw, lips, tongue, throat and brain develop over the first nine months of life, infants learn how to use the voice to mimic simple controlled sounds, such as "ba ba" or "da da." During this time, they learn to regulate the action of muscles in the face, mouth, neck, chest, and abdomen to produce speech-like sounds. At first, these sounds are filled with nonsense syllables. Eventually, children begin to use words that others can understand. The responses they get encourage them to speak more and more. With practice, words become more understandable.

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

What Can Go Wrong?

Speech disorders arise from many different conditions and have a wide range of causes. Two main parts of the brain are involved in producing and understanding speech: Broca's area and Wernicke's area. Broca's area coordi-nates the muscles of the lips, tongue, jaw, and vocal cords to produce understandable speech. Wernicke's area controls the comprehension, or understanding, of others' speech. Damage to these or other portions of the brain—or to the nerve connections to the organs that make speech (tongue, mouth, chest, and so forth)—can result in disordered speech.

Stroke, trauma, or infection may be the root cause of these disruptions. Severe mental retardation often has a negative impact on speech development. In some cases, anatomy plays 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. Many children show delays in developing speech, a condition that frequently is out-grown. Often the cause of a child's speech disorder is never known.

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.

Articulatory Disorders

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 the ages of 2 and 3 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 most well-known lispers is the cat, Sylvester, featured in the Tweety Bird cartoons, whose favorite exclamation is "thuffering thuccotash!"

* dementia (de-MEN-sha) is a general loss of intellectual abilities involving impairment of memory, judgment and abstract thinking, and often changes in personality.

Lisping can happen for a variety of reasons: an abnormal number or position of teeth; unconscious imitation of other lispers; defects in the structure of the mouth, such 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 to make the sound correctly.


Stuttering often begins in early childhood and may persist into adulthood. People who stutter repeat certain speech sounds, or 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. Over 3 million Americans stutter, and most began stuttering between the ages of 2 and 6.

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 words out. 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.

Sign Languages

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 or signed language. Currently, there are three signed languages used in the United States.

In the mid-1700s, a French educator working with poor deaf children developed a system for spelling out French words with a manual alphabet, expressing whole concepts with one or two hand signs, and adding emphasis with standardized facial expressions. 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 now is American Sign Language (ASL). Gallaudet University in Washington, D.C., is named for Thomas Gallaudet.

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

Cued Speech, developed in 1966 by the American scientist R. Orin Cornett, uses hand signs to represent sounds, rather than letters or concepts. It is used in conjunction with mouthing of word cues, such as the most prominent vowel in each word.

Researchers have found that stuttering affects males about four times more often than females. 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 young children outgrow their stuttering, and it is estimated that fewer than I percent of American adults stutter. However, children who do not outgrow stuttering by the time they enter elementary school may need speech therapy. Many people have overcome stuttering and gone on to achieve success in careers that require public speaking, acting, and singing.

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) not only have trouble speaking, but also have 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.

Broca's aphasia

Broca's aphasia results from damage to the area that coordinates the muscles of the lips, tongue, jaw, and vocal cords that produce understandable speech. 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. These people 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 speak or to comprehend language.

How Are Speech Disorders Diagnosed and Treated?


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 health care providers.

Successful Speakers

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 share the problem of stuttering. Their public successes point to one of the unique features of stuttering: although it is a problem in everyday conversation, often it disappears when someone is singing or delivering memorized lines. Further, people who stutter often can learn strategies for overcoming the problem as they grow older.

James Earl Jones

In his autobiography, 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 has provided the voices for Darth Vader in Star Wars and King Mufasa in the animated Lion King, and has acted on stage and in numerous films.

John Stossel

Asa 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 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 speech clinic in Roanoke, Virginia. Stossel now is a spokesman forthe National Stuttering Association.

Speech-language therapists often make an initial evaluation to help determine what problems exist and the best way to treat them. Because talking and hearing are closely related, children with speech disorders often undergo a hearing evaluation done by an audiologist (aw-dee-OL-o-jist), who is educated in the study of the hearing process and hearing loss. The audiologist can determine if a person has a hearing loss, the type of loss, and recommend how the person can make the best use of any remaining hearing. When the speech disorder is caused by damage to the nerves or brain, a neurologist may also be involved in the evaluation process.


People with aphasia often benefit from speech-language therapy, which focuses on helping people make the most of their remaining abilities and learning 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 portable, communication possibilities for aphasic and dysphasic adults will continue to expand.

See also
Alzheimer's disease
Brain tumor
Cleft palate
Deafness and Hearing Loss
Mental Retardation
Viral infections



Bobrick, Benson, and Deborah Baker, Eds. Knotted Tongues: Stuttering in History and the Quest for a Cure. New York: Kodansha, 1996.

Jezer, Marty. Stuttering: A Life Bound Up in Words. New York: Basic Books, 1997.


U.S. National Institute on Deafness and Other Communication Disorders, National Institutes of Health, 31 Center Drive, MSC 2320, Bethesda, MD 20892-2320.
Telephone 800-241-1044

American Speech-Language-Hearing Association (ASHA), 10801 Rockville Pike, Rockville, MD 20852.
Telephone 888-321-ASHA

National Aphasia Association, 156 Fifth Avenue, Suite 707, New York, NY 10010.
Telephone 800-922-4622

National Stuttering Project, 5100 East LaPalma Avenue, Suite 208, Anaheim Hills, CA 92807.
Telephone 800-364-1677

Stuttering Foundation of America, P.O. Box 11749, 3100 Walnut Grove Road, Number 603, Memphis, TN 38111.
Telephone 800-992-9392

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