See the Speech Sound Disorders Evidence Map for summaries of the available research on this topic.
The scope of the Speech Sounds Disorders: Articulation and Phonology page is articulation and phonological disorders and error types with no known cause, in preschool and school-age children (3-21). Separate pages will be developed in the future for several of the disorders and conditions known to cause speech sound problems, including motor-based disorders (CAS and dysarthria), structurally based disorders (e.g., cleft-palate), syndromes (e.g., Down), and sensory-based conditions (e.g., hearing loss).
Speech sound disorders is an umbrella term referring to any combination of difficulties with perception, motor production, and/or the phonological representation of speech sounds and speech segments (including phonotactic rules that govern syllable shape, structure, and stress, as well as prosody) that impact speech intelligibility.
Known causes of speech sound disorders include motor-based disorders (apraxia and dysarthria), structurally based disorders and conditions (e.g., cleft palate and other craniofacial anomalies), syndrome/condition-related disorders (e.g., Down syndrome and metabolic conditions, such as galactosemia), and sensory-based conditions (e.g., hearing impairment).
Speech sound disorders can impact the form of speech sounds or the function of speech sounds within a language. Disorders that impact the form of speech sounds are traditionally referred to as articulation disorders and are associated with structural (e.g., cleft palate) and motor-based difficulties (e.g., apraxia). Speech sound disorders that impact the way speech sounds (phonemes) function within a language are traditionally referred to as phonological disorders; they result from impairments in the phonological representation of speech sounds and speech segments—the system that generates and uses phonemes and phoneme rules and patterns within the context of spoken language. The process of perceiving and manipulating speech sounds is essential for developing these phonological representations.
Often, it is not possible to determine the underlying cause of a speech sound disorder or to differentiate articulation from phonological etiology. Nevertheless, this Portal Page maintains the distinction for descriptive purposes and because distinguishing each error type may have practical applications for diagnosis and treatment approaches.
See Speech Characteristics: Selected Populations [PDF] for a brief summary of selected populations and characteristic speech problems. Note that the procedures and approaches detailed in this page may also be appropriate for assessing and treating speech sound disorders in children with these known disorders and conditions. When available, evidence and/or expert opinion for specific populations are included in this document; all populations may not be represented in these statements.