Articulation and Phonology Disorders 27when they attempt to produce adult speech. To treat a communication disorder, the clinician helps
the child discover adult phonology. More than one sound is used to teach the phonological rules.
This approach is particularly useful for children who have more than one articulation disorder
and for those with impaired intelligibility. Figure 2-3 shows syllable structure, substitution, and
harmony pro cesses and their ages of normal extinction (Tanner, Culbertson, & Secord, 1997).
Phoneme Acquisition Ages
As Figure 2-4 shows, the sequence of phoneme acquisition in children is relatively invariant,
whereas the rate is highly variable. In all languages, phonetic duplications are the most common
types of first words. In En glish, most children’s first words are phonetic duplications such as
mama and dada. According to Tanner et al. (1997), 75% of children have acquired the following
phonemes in all positions of words (initial, medial, final) by age 3 years: /m/, /h/, /w/, /n/, ng, and
/f/. Seventy- five percent of children have acquired the phonemes /ʒ/ and /ð/ in all three positions
of words by age 7 years. Consequently, 75% of children learn to produce the phonemes of En glish
in the initial, medial, and final positions of words between 3 and 7 years of age. The two most
common misarticulated consonant phonemes, /r/ and /s/, are established at 4 years, 6 months
and 4 years, 9 months, respectively, by 75% of children in all three positions of words.
Errors in Articulation
Although children may substitute, distort, add, and omit vowels during speech production,
the most common articulatory errors involve consonants. Vowels and diphthongs are mastered by
most children before the age of 4 years (Tanner et al., 1997). Phoneme acquisition sequence and
rate may also have minor variance by geographic region— for example, northern versus southern
Figure 2-3. Developmental Articulation and Phonology Profile. (Reprinted with permission from Academic
Communication Associates.)