Monday, 3 November 2014

Phonological Development

Phonological development (or phonemic development) is the gradual development of an ‘organised’, adult-like system of sound contrasts. Phonological development is thought to have three aspects which include the way the sound is stored in the child’s mind, the way the way the sound is actually said by the child and the phonological rules or processes that ‘map’ the two above.
Phonetic development is the gradual acquisition of the ability to articulate speech sounds (e.g. ‘p’, ‘b’, ‘t’, etc.) and structures (e.g. consonant clusters such as ‘fl’ and ‘skw’). It’s often referred to as articulation development.

Acquiring the sound system of language is an on-going and complex task in the first five years of life. It works at two different levels. First, they need to gain mastery over the nerves that control their vocal tract in order to produce their words accurately (phonetic ability). Second, children need to learn what sounds and combination of sounds are permissible in their language (phonological knowledge).

The course of phonetic ability
1. At birth, infants:
 - discriminate their native language from a foreign language
 - discriminate between two foreign languages
 - can count syllables and thus vowels in a word
 - perceive accent
2. At 1 month, infants discriminate between consonants
3. At 6-8 months, infants start to babble (vocally or manually)
4. At 8-10 months, infants:
 - vowels quality is influenced by the ambient language
 - sensitivity to foreign consonantal contracts starts to decline
5. At 10-12 months, infants:
 - cannot discriminate consonant contracts belonging to a foreign language
 - use a repertoire of consonants during babbling that is influence by their native language
 - produce their first words

Patterns in phonological development: at first, children tend to make simplifications that allow them to reduce the number of sounds and contrasts between sounds that they have to deal with. These simplification processes fall into three main types; substitution processes, assimilatory processes and syllable structure processes. Substitution processes involve substituting one sound segment with another which includes stopping (a fricative or affricative consonant is replaced by a stop consonant. The child will usually try to keep the place of articulation as similar to the target as possible, however, it’s easier for children to produce fricatives with stops), fronting (back consonants are replaced with ones that are articulated further forward in the mouth), gliding (liquid sounds ‘I’ or ‘r’ are replaced by glides ‘w’ or ‘j’) and vocalisation (a vowel replaces a syllable consonant).
Assimilatory processes where one sound segment are made more similar to or sometimes exactly the same as another one. Including consonant voicing (voiceless consonants followed by vowels, especially at the beginning of a word, will tend to become voiced like vowels), consonant de-voicing (consonants at the ends of words to become voiceless, assimilating to silence) and consonant harmony (a consonant will assimilate to another consonant in the word. More often, it is an early consonant that assimilates to a later one, although the reverse can also happen).
The syllable structure process is where the child adds or removes sounds or alters the structure of the syllable in some way. They reflect a preference by young children for CVCV (consonant vowel, consonant vowel) patterns. This includes consonant cluster reduction (where two or more consonants occur in a cluster, the child will reduce this to a single consonant), vowel epenthesis (children sometimes break up consonant clusters by deleting one of the consonants, but by adding a vowel to separate them), deletion of final consonants, syllable deletion (this usually involves deletion of the unstressed syllable(s) in a word, but can occasionally involve the deletion of a stressed syllable), reduplication (in a multi-syllable word, the child will repeat a CV syllable, usually the initial syllable). These simplification processes are quite systematic and can be observes in children all over the world, regardless of the language they are acquiring.

Jakobson (1941/68) proposed that infants babble the sounds of all language, also that there is discontinuity between babbling and first words and that phonemes are acquired in a universal order.
Transitional probabilities for within-word phonemes or syllable sequences are necessarily higher than for sequences across word boundaries. Therefore, recurrent pairs of sounds or syllables are likely to form part of the same word. Adults can learn the transitional probabilities and therefore segment out the “words” of a nonsense language presented aurally with no prosodic information. Their performance improves with the addition of one prosodic cure, final syllable lengthening (Saffran, Newport and Aslin, 1996).


Phonological delay: when a child is continuing to simplify their speech (using phonological processes) beyond the typical ages of use. A child with a severe phonological delay may be simplifying his speech so much that they are only producing a few different sounds when they should be able to produce many sounds (which is when the “classes” of sounds can come in handy). Children with phonological delays tend to be quite hard to understand, especially to strangers as parents or caregivers often learn their child’s patterns and therefore can understand them better.
According to Speech-Language Pathologist Caroline Bowen, who has done research and written books on the subject, there are five possible causes for phonological delay based on the research to date:

Phonological development (or phonemic development) is the gradual development of an ‘organised’, adult-like system of sound contrasts. Phonological development is thought to have three aspects which include the way the sound is stored in the child’s mind, the way the way the sound is actually said by the child and the phonological rules or processes that ‘map’ the two above.
Phonetic development is the gradual acquisition of the ability to articulate speech sounds (e.g. ‘p’, ‘b’, ‘t’, etc.) and structures (e.g. consonant clusters such as ‘fl’ and ‘skw’). It’s often referred to as articulation development.
Acquiring the sound system of language is an on-going and complex task in the first five years of life. It works at two different levels. First, they need to gain mastery over the nerves that control their vocal tract in order to produce their words accurately (phonetic ability). Second, children need to learn what sounds and combination of sounds are permissible in their language (phonological knowledge).
The course of phonetic ability
1. At birth, infants:
 - discriminate their native language from a foreign language
 - discriminate between two foreign languages
 - can count syllables and thus vowels in a word
 - perceive accent
2. At 1 month, infants discriminate between consonants
3. At 6-8 months, infants start to babble (vocally or manually)
4. At 8-10 months, infants:
 - vowels quality is influenced by the ambient language
 - sensitivity to foreign consonantal contracts starts to decline
5. At 10-12 months, infants:
 - cannot discriminate consonant contracts belonging to a foreign language
 - use a repertoire of consonants during babbling that is influence by their native language
 - produce their first words
Patterns in phonological development: at first, children tend to make simplifications that allow them to reduce the number of sounds and contrasts between sounds that they have to deal with. These simplification processes fall into three main types; substitution processes, assimilatory processes and syllable structure processes. Substitution processes involve substituting one sound segment with another which includes stopping (a fricative or affricative consonant is replaced by a stop consonant. The child will usually try to keep the place of articulation as similar to the target as possible, however, it’s easier for children to produce fricatives with stops), fronting (back consonants are replaced with ones that are articulated further forward in the mouth), gliding (liquid sounds ‘I’ or ‘r’ are replaced by glides ‘w’ or ‘j’) and vocalisation (a vowel replaces a syllable consonant).
Assimilatory processes where one sound segment are made more similar to or sometimes exactly the same as another one. Including consonant voicing (voiceless consonants followed by vowels, especially at the beginning of a word, will tend to become voiced like vowels), consonant de-voicing (consonants at the ends of words to become voiceless, assimilating to silence) and consonant harmony (a consonant will assimilate to another consonant in the word. More often, it is an early consonant that assimilates to a later one, although the reverse can also happen).
The syllable structure process is where the child adds or removes sounds or alters the structure of the syllable in some way. They reflect a preference by young children for CVCV (consonant vowel, consonant vowel) patterns. This includes consonant cluster reduction (where two or more consonants occur in a cluster, the child will reduce this to a single consonant), vowel epenthesis (children sometimes break up consonant clusters by deleting one of the consonants, but by adding a vowel to separate them), deletion of final consonants, syllable deletion (this usually involves deletion of the unstressed syllable(s) in a word, but can occasionally involve the deletion of a stressed syllable), reduplication (in a multi-syllable word, the child will repeat a CV syllable, usually the initial syllable). These simplification processes are quite systematic and can be observes in children all over the world, regardless of the language they are acquiring.
Jakobson (1941/68) proposed that infants babble the sounds of all language, also that there is discontinuity between babbling and first words and that phonemes are acquired in a universal order.
Transitional probabilities for within-word phonemes or syllable sequences are necessarily higher than for sequences across word boundaries. Therefore, recurrent pairs of sounds or syllables are likely to form part of the same word. Adults can learn the transitional probabilities and therefore segment out the “words” of a nonsense language presented aurally with no prosodic information. Their performance improves with the addition of one prosodic cure, final syllable lengthening (Saffran, Newport and Aslin, 1996).

Phonological delay: when a child is continuing to simplify their speech (using phonological processes) beyond the typical ages of use. A child with a severe phonological delay may be simplifying his speech so much that they are only producing a few different sounds when they should be able to produce many sounds (which is when the “classes” of sounds can come in handy). Children with phonological delays tend to be quite hard to understand, especially to strangers as parents or caregivers often learn their child’s patterns and therefore can understand them better.
According to Speech-Language Pathologist Caroline Bowen, who has done research and written books on the subject, there are five possible causes for phonological delay based on the research to date:
1. The child find the sound patterns of language totally confusing and cannot make out sound details from the overall pattern of sounds in language
2. The child's speech maturation may be severely delayed
3. The restricted speech system become "habit", suppressing further speech maturation
4. The child has poor perception and awareness of how speech sounds, and the difficulty other people have understanding them when they talk
5. The child has a specific difficulty initiating changes in their sound system, and knowing how to organise their sound in a consistent way


Table showing phonological development: 
http://www.srsdeaf.org/Downloads/SpeechLanguage_Development_Chart.pdf