Non-developmental errors occurred in the speech
of children with ASD regardless of whether their
GFTA-2 standard scores were within or outside the
normal range. Despite some children having standard
scores in the normal range, it was possible for
them to produce errors consistently. The GFTA-2
samples each consonant a maximum of three times,
(initial, medial and final word positions) unless it
appears in a consonant cluster. However, should a
child make an error on one phoneme in each word
position (resulting in a raw score of three) he or she will still achieve a standard score in the normal range.
Several children therefore produced errors consistently
but achieved normal scores. For example, one
child aged 7;5 used the developmental process of
post-alveolar fronting consistently (/R / produced as
[s]) but achieved a normal standard score even
though [R ] is usually acquired by 5;0 to 5;5 (Dodd,
2005). Where errors occur on phonemes that are
frequent in the ambient language, such as /s/, the
impact on speech is more pervasive and noticeable to
listeners than for errors affecting less frequently
occurring phonemes, such as affricates. For example
one child with a standard score in the normal range
consistently produced /s/ as a voiceless lateral
fricative (a lateral lisp), because /s/ is a frequently
occurring phoneme (Shriberg & Kwiatkowski, 1982)
this results in speech that is noticeably different from
the norm.