Phonological development is the process of learning to speak and is most closely associated with children. The physiological systems, which take part in this process, are the auditory and the vocal systems. The auditory system includes the ears, ear canal and brain. The vocal system includes the vocal chords, the throat, the mouth, teeth and tongue. The jaw is included in the vocal system due to the necessary jaw movements needed to create sounds, which make words.
The first phase of phonological development is called the pre-representational stage. This stage of speech begins after a child has spent a year listening to others speak and collecting his own interpretation of auditory input. A child will enter this stage at around 14 months of age; as the child lacks the proper vocal system physiology to speak properly, the sounds will be babbling and very simple consonant sounds. These sounds are referred to as formulaic, echolalia and mimic expressions.
The second phase of phonological development is called the representational stage. Children enter this stage around the 24th month. Vocal chords begin to strengthen as children begin to learn how to place the tongue and teeth for proper sound production. During this stage, children cannot pronounce a consonant against a consonant, such as in the word spaghetti. Often, children will replace the “sp” combination with a single consonant sound, giving them a consonant against a vowel. Young phonological learners are not able to pronounce a consonant against a consonant; they can only pronounce a consonant against a vowel.
Target grammar is the third, and final, stage of phonological development. This stage finds children knowing how to properly place the tongue against the teeth, as well as discovering how to place a consonant next to a consonant in a word and make the correct sounds to create the proper word. Vocabulary begins to expand during this stage. Phonics and reading are often introduced, though the child cannot cognitively read until he has been in this stage for a few years. It is common for a child to use words incorrectly, as his vocabulary expands faster than his ability to grasp the definition of every single word.
Problems found within each phase of phonological development will cause problems in later stages if left untreated. Hearing problems in infants delay speech, as the child cannot hear well enough to begin the first phase. Children who are neglected will miss the second stage completely; if they do not hear the words, they will not learn pronunciations. Physiological issues, such as cleft palates, issues with the tongue or jaw problems will impede a child's progression to stage three.