Based on research in the area of speech development, children are expected to develop and produce speech sounds by a specific age to be considered within normal limits. For example, the speech sounds /b/, /p/, /m/, /d/, and /k/ are typically expected to develop by three years of age. While speech sounds may develop slightly differently for all children, if a child has not developed age-appropriate sounds by the expected age they are considered to have a speech delay. Speech delay is characterized by reduced intelligibility and increased risk for broader communication and academic difficulties. Possible causes include: genetics, early history of recurrent ear infections, motor speech involvement associated with either developmental apraxia of speech or with mild dysarthria, and developmental cognitive involvement.
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An articulation disorder involves difficulty making sounds. Sounds can be substituted, left off, added, or changed. These errors may make it hard for people to understand a child’s message. Young children often make speech errors. For instance, many young children sound like they are making a "w" sound for an "r" sound (e.g., "wabbit" for "rabbit") or may leave sounds out of words, such as "nana" for "banana." The child may have an articulation disorder if these errors continue past the expected age.
Not all sound substitutions and omissions are speech errors. Instead, they may be related to a feature of a dialect or accent. For example, speakers of African American Vernacular English (AAVE) may use a "d" sound for a "th" sound (e.g., "dis" for "this"). This is not a speech sound disorder, but rather one of the phonological features of AAVE. Native Spanish speakers may substitute a "b" sound for a "v" sound (e.g. "bery" for "very"). Again, this is not considered disordered articulation, but, rather, a phonological feature of a Spanish accent.
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Phonological Process Disorders
A phonological process disorder involves patterns of sound errors. For example, substituting all sounds made in the back of the mouth like "k" and "g" for those in the front of the mouth like "t" and "d" (e.g., saying "tup" for "cup" or "das" for "gas").
Another example is cluster reduction, which involves words starting with two consonants, such as broken or spoon. When children use only one of the sounds (e.g., "boken" for broken or "poon" for spoon), it is more difficult for the listener to understand the child. While it is common for young children learning speech to leave one of the sounds out of the word, it is not expected as a child gets older. If a child continues to demonstrate these patterns, they may have a phonological process disorder.
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