The speech sound development in children

Introduction

Speech is the production of sounds by speech organs. It is a verbal expression of language. Language is a set of socially shared rules in forming the symbolic communication system, e.g. English, Cantonese. Children who have speech sound disorder are characterized by inappropriate errors in speech production, while those with language impairment have deficit in receptive or/and expressive language ability. Articulation problem is one of the developmental problems commonly found in children. Many parents question about if the speech sound errors of their children will be self-corrected with time, and when should they receive speech therapy. Before answering these questions, we have to understand the normal speech sound development.

Speech mechanism and speech sound development

A speech sound is generated by speech organs. When air passes through the vocal folds, the vocal folds vibrate and generate a sound. This sound will be modified by articulators, like jaw, lips, tongue, palate, etc. Different placement of articulators (place of articulation), different nature and type of airflow obstruction (manner of articulation) can result in different speech sounds. For example, initial consonant /p/ in “pen” is generated by lip closure, while initial consonant /k/ in “Ken” is generated by raising the tongue base to the soft palate.

In Cantonese, there are 19 initial consonants, 11 vowels and 11 diphthongs (i.e. combined by two vowels, e.g. /iu/ in “錶” /piu/). By the age of three, many children have acquired the vowels and diphthongs. In the acquisition of initial consonants, the place and manner of articulation have a developmental trend. Bilabials (e.g. /p/ in “爸” /pa/) usually appear before velars (e.g. /k/ in “加” /ka/) and plosives (e.g. /t/ in “打” /ta/) generally appear before affricates (e.g. /ts/ in “知” /tsi/). Therefore, bilabial plosive /p/ is acquired before velar plosive /k/ and alveolar plosive /t/ is acquired earlier than alveolar affricate /ts/1. The following table shows the age of acquisition of different speech sounds:

Table: Speech sound development in Cantonese2

Age group Standard: ≥ 75% acquisition criterion
Boys Girls
2 years and 6 months p(爸), t(打), h(蝦), w(話),
m(媽) 		p(爸), h(蝦), j(也), w(話),
m(媽), ŋ/Ø(我)
3 years old f(花), j(也), ŋ/Ø(我) ph(爬), t(打), kw(瓜), f(花),
l(啦)
3 years and 6 months ph(爬), th(他), k(哥), kh(卡), kw(瓜), kwh(跨), ts(姐), l(啦) th(他), k(哥), kh(卡),
kwh(跨), ts(姐)
4 years old tsh(車) tsh(車)
4 years and 6 months s(沙) s(沙)

Common speech sound errors

Different speech sounds appear gradually at different ages. Therefore, many children have speech sound errors during the development of language as they haven't reached the age to produce certain sounds. Usually their speech intelligibility will improve across time. At the age of five, many children will have clear speech production. However, some children continue to have speech sound errors, which affect their communication with others and need speech therapy service. There are different types of speech sound errors, and here we will explain six types2.

  • Lisping - putting the tongue in wrong position (e.g. tongue protrusion) in producing /s/ sound.
  • Stopping - replacement of fricatives and affricates with stops (e.g. see -> dee).
  • Fronting - replacement of back sounds with front sounds (e.g. car -> tar).
  • Delabialization - replacement of labiovelars with velars (e.g. /kwa/ (瓜) -> [ka] (家)).
  • Deaspiration - replacement of aspirated sounds with unaspirated sounds (e.g. /pha/ (爬) -> [pa]/ (爸)).
  • Backing - replacement of front sounds by back sounds (e.g. tin -> kin).

Causes of speech sound disorder

Speech sound disorder occurs when the speech sound errors persist beyond the age of acquisition of a target sound. Here we will list out different causes for speech sound disorder:

  • Oral motor functional problem: The child is able to achieve non-verbal oral motor muscle exercise, but cannot apply to the respective speech sounds; e.g. can bite on lower lip, but produce /fa/ (花) as [pa] (爸).
  • Oral motor problem: Oral motor muscles weakness, cleft palate, tongue tie.
  • Sensory factors: Hearing loss, hyper/ hypo sensitivity of oral muscles.
  • Neurological factors: Motor speech disorders (e.g. apraxia), cerebral palsy
  • Environmental factors: Caregivers or siblings with speech sound disorder
  • Unknown factors

Facilitative environment to enhance speech sound development

The acquisition of speech sounds follows a developmental trend. Many children will have unintelligible speech in early stage, which will be resolved over time. A facilitative environment is always beneficial to their learning. Children learn speech by imitating people around them. Parents are encouraged to speak to their children face-to-face to provide visual support (the mouth shape) to them. In addition, parents can encourage children to speak slower to allow more time for the articulators to shape different sounds. If a wrong sound is produced, parents can demonstrate the correct sound to their children. However, they are not advised to over-regulate children's wrong production, e.g. requiring children to imitate the correct sounds for many times or regulate the wrong production at a stage too early since it may place negative impact on children's self confidence in speech.

The importance of diet and oral motor development is sometimes overlooked. The diet of children should be modified accordingly as they grow up. By chewing different textures of food, jaw muscles can be strengthened. For more information about children's diet, please refer to the booklet “Healthy Eating for 6 to 24 month old children (3) Ready to go (12- 24 months)”. Children love learning through play. Some play activities, like blowing bubble, pinwheel, toy horns, may also promote oral functioning.

It is advised to seek speech therapist for assessment if children's speech sound errors persist at an age after the age of acquisition.

FAQ from parents

  1. Q: Does my child have tongue tie? Is this the cause of his speech problem?

    A: Many people would mistake unclear articulation as tongue tie. Tongue tie is a structural problem, it refers to a short lingual frenulum (a band of tissue connecting the underside of the tongue with the floor of the mouth), which restricts the mobility of tongue tip. When the child protrudes his/her tongue, the front of the tongue appears like a heart-shape. Tongue tie is not a major cause for speech sound disorder.

  2. Q: Why does my child still drool? What should I do with it?

    A: Drooling can be due to excessive saliva production, oral motor muscles weakness, sensory problem or nervous system disorders. For mild case, when the child drools, parent can guide him/ her to close the mouth and swallow the saliva. For severe case, please consult your doctor.

  3. Q: Does my child have hearing problem which may cause speech sound disorder?

    A: Hearing impairment is one of the factors affecting children's speech sound learning. Children with recurrent otitis media (middle ear infection) are at risk of hearing loss. If the child shows signs of hearing problem, e.g. always needs others to repeat their words, always complains of not hearing properly, cannot distinguish similar spoken word pairs (e.g. pen VS Ben), you may seek doctor's consultation and arrange for referral to an audiologist or ear, nose, and throat (ENT) specialist, if needed. 

  4. Q: If parents speak with an accent, will it lead to speech sound disorder in their children?

    A: In Hong Kong, dialectal speech is common in parents whose mother tongue is Putonghua or other Chinese dialects. Children speaking with an accent are not regarded as having speech sound disorder. Usually the longer the children get exposed to local environment, the lesser the dialectal effect will be from the parents.

References

  1. To, C. K. S., Cheung, P. S. P., & McLeod, S. (2013). A Population Study of Children's Acquisition of Hong Kong Cantonese Consonants, Vowels, and Tones. Journal of Speech, Language, and Hearing Research, 56, 103-122.
  2. Cheung, P. S. P., Ng, A., & To, C. K. S. (2006). Hong Kong Cantonese Articulation Test. Hong Kong: Language Information Sciences Research Centre, City University of Hong Kong.

Related resources

The Hong Kong Association of Speech Therapists (HKAST):
https://speechtherapy.org.hk/Resources.html

American Speech-Language-Hearing Association (ASHA):
http://www.asha.org/public/speech/disorders/SpeechSoundDisorders/