Typical Speech Development
THE GRADUAL ACQUISITION OF THE SPEECH SOUND SYSTEM
Copyright © Caroline Bowen 1998 All rights reserved

Citing this article
This page contains an article about speech development. Cite it as: Bowen, C. (1998). Typical speech development: the gradual acquisition of the speech sound system. Retrieved from http://www.speech-language-therapy.com/acquisition.html on (date).

Anyone who has been around children who are under 5 years of age will know that their speech sounds are not pronounced correctly all the time. In fact small children's speech can be quite difficult to understand because their sound system is not yet organised like adult speech.

Articulation and Phonology Norms
Many researchers have studied children's acquisition of individual speech sounds (phonetic development), and the way they organise these sounds into speech patterns (phonemic or phonological development). Drawing on this vast a varied body of research, Dr Sharynne McLeod of Charles Sturt University in Australia compiled the pdf file here, [Adobe Reader Required]. It contains an overview of typical speech development from a range of researchers around the world, working from a variety of theoretical perspectives. 

Developmental norms and target selection
Gregory L. Lof PhD presented a fascinating poster entitled Confusion about speech sound norms and their use in an online conference sponsored by Thinking Publications in 2004, exploding a few myths about normal (or 'normative') expectations and when to start therapy for particular speech sounds.

Critical information
For Speech-Language Pathologists, a detailed understanding of typical ('normal') development is critical to the understanding of delayed and disordered development.

Intelligibility
Table 1 provides a rough rule of thumb for how clearly your child should be speaking. If you are in doubt about your own child's speech sound development an assessment by a speech-language pathologist will quickly tell you if your child is 'on track' and making the right combination of correct sounds and 'errors' for their age. Table 1 is available separately here. See also: speech intelligibility from 12 to 48 months for a more detailed discussion.

Phonological development
The gradual process of acquiring adult speech patterns is called phonological development.

Phonological processes
All children make predictable pronunciation errors (not really 'errors' at all, when you stop to think about it) when they are learning to talk like adults. These 'errors' are called phonological processes, or phonological deviations. 

In Table 2 are the common phonological processes found in children's speech while they are learning the adult sound-system of English. Table 2 is available separately here.

Elimination of phonological processes
Phonological processes have usually 'gone' by the time a child is five years of age, though there is individual variation between children. 

Table 3 lists the ages by  which each of the processes are normally eliminated. Ages are expressed as years;months. For example, 3;6 means 3 years 6 months. Table 3 is available separately here.

Phonetic development
Table 4 outlines the ages by by which 75% of children in a carefully conducted study accurately use individual speech sounds in single test-words. These norms were established for a population of Australian children by Kilminster and Laird (1978).  

In column 3,  the term 'voiced' refers to the vibration of the vocal cords while the sound is being made. The term 'voiceless' is applied to sounds that are made without vocal cord vibration. The terms fricative, glide, stop, nasal, liquid and affricate refer to the way the sounds are made, or the "manner of articulation". The International Phonetic Alphabet Charts summarise this information here.

References
Bowen, C, (1998). Developmental phonological disorders. A practical guide for families and teachers. Melbourne: ACER Press.

Grunwell, P. (1997). Natural phonology. In M. Ball & R. Kent (Eds.), The new phonologies: Developments in clinical linguistics. San Deigo: Singular Publishing Group, Inc.

Kilminster, M.G.E., & Laird, E.M. (1978) Articulation development in children aged three to nine years. Australian Journal of Human Communication Disorders, 6, 1, 23-30. 

Lof, G.L. (2004). Confusion about speech sound norms and their use. Thinking Publications Online Conference. www.thinkingpublications.com/LangConf04/OLCIntro.html Accessed April 21 2004.

Lynch, J.I., Brookshire, B.L., & Fox, D.R. (1980). A Parent - Child Cleft Palate Curriculum: Developing Speech and Language. CC Publications, Oregon.

Child speech professional discussion
Phonological Therapy is a discussion group for clinicians, including student clinicians, speech and language researchers and university teachers. Most participants are Speech-Language Pathologists and Linguists. Members explore theoretical and research issues related to developmental phonological disorders, childhood apraxia of speech, and other childhood speech sound disorders, and their clinical management. Although interested consumers are most welcome to join, please note that the group is for professional discussion not consumer advice and support.

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