Phonological development refers to children's acquisition of English phonemes (sounds). There are 40 different phonemes in English (consonants and vowels) and the child acquires these at different rates.
The Pre-Verbal stages
The preverbal stages provide an outline of vocal development during the first year. However, the preverbal stages are only a theory and babies vary so it is not 100% accurate.
1) Biological noises - 0-8 weeks. Vomiting, coughing, burping and the most important - crying. These are common to the whole human race: Icelandic burps or Thai cries do not exist.
2) Cooing and laughing - 8-20 weeks. Produced when the baby is in a settled state, these are short vowel-like sounds. 'Quieter, lower pitched and more musical than biological noises' - David Crystal. Some consonant-like sounds come from the back of the throat, the baby is beginning to develop control over vocal muscles.
3) Vocal play - 20-30 weeks. A controlled single vowel-like or consonant-like sound. More varied than babbling but much less controlled.
4) Babbling - 25-50 weeks. The baby produces phonemes, often in the form of combinations of vowels and consonants e.g. 'ma', 'ba', 'ga'. These sounds are largely those that appear in the child's native language.
Variegated babbling: where the sounds change during a single babbled string e.g. 'ba-ma-mi'
Reduplicative babbling: Where the infant makes the same sound repeatedly e.g. 'baba', 'gaga'
5) Melodic utterance - 9-18 months. Melody, rhythm and intonation develop. Parents assume that these sounds have different functions: questioning, exclaiming, greeting, etc. Babies of different nationalities sound increasingly different from eachother at this stage.
Easy VS difficult consonants
Bilabial sounds have a place of articualtion of both lips. e.g. /b/, /p/, /m/, /w/.
Velar sounds have a place of articulation of back of the mouth and tongue. e.g. /g/, /k/
Dental sounds are harder for children to pronounce. They have a place of articulation of the upper and lower teeth, and tongue. e.g. /ð/
Plosive sounds have a manner of articulation of complete blocking and release of the air. e.g. /p/, /k/, /g/, /d…