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and exploration begets a path that is cyclic and nonmono- are common in the early years of speech production; over
tonic (Green and Nip, 2010), meaning that children do not 15% of three-year-old children have speech sound disorders
seamlessly transition from an inaccurate form to an accurate with no known cause (i.e., not attributable to hearing loss
form. Instead, speech acquisition occurs in cycles character- or neurological issues; Campbell et al., 2003). The preva-
ized by periods of rapid acceleration and deceleration, with lence of this disorder decreases by school age, with nearly
inflection points that alternate between weightings on “pre- 4% of 6-year-old children exhibiting speech sound disorders
cise” and “accurate” goals (McAllister Byun et al., 2016). The (Shriberg and Kwiatkowski, 1994). The vast majority of pre-
progress advances toward what will be rather than building school children with speech sound disorders do not seem to
slowly from the enhancements of the current state. Fiona have atypical speech motor control (Vick et al., 2014), which
transitioned from a relatively stable period where the mas- suggests that these ongoing errors are part of the individual-
tered, but inaccurate, “Sahmi” production was produced with ized constraints and strategies employed by children. For ex-
precision. Working toward the more complex, “Fiona” pro- ample, Fiona’s five-year-old sister, Annabel, was a compara-
duction required a period of relative instability, or variability, tively precocious talker, producing her first words before her
where the productions were neither accurate nor precise as first birthday. Her first productions were likely facilitated by
she worked toward a closer approximation of the adult tar- her responsive and facilitating sister (see Multimedia File 7
get. For Fiona, this period of instability was characterized by at acousticstoday.org/mm-vick), but her substitution of the
her referring to herself with productions that began to sound “t” and “d” sounds for “l€’ and “g” certainly were not emu-
something like “Feena.” A period of relative stability and pre- lations of how Fiona produces these sounds. Sure enough,
cision followed, with “Feena” being closer to accurate but still as Annabel approached her sixth birthday, these errors were
missing the mark. Producing the accurate “Fiona” required resolved with the help of speech therapy.
mother Fenod of mslabdnyt followed’ fi_mlly' by an accurate Speech sound disorders that persist beyond the preschool
and Precise tarsal that she sun uses lo “"5 day years are of great concern because they are associated with
This cycling through periods of stability and instability with later challenges in reading, spelling, and literacy (Lewis et al.,
different levels of precision and accuracy has been support- 2015). When speech errors persist into later childhood (1%
ed empirically as well using the motion capture technology of 8-year-old children experience this; Wren et al., 2013),
to quantify the stability and instability in measures of moVe- there is additional risk of social isolation, bullying from
ment variability in a group of over 60 preschool-aged chil- peers, and behavioral challenges that stem directly from the
dren (Vick et al., 2012). The measures from this large sample speech errors (e.g., Lindsay et al., 2002), all of which cre-
were used to subgroup the children. The result was that the ate significant challenges with quality of life. The underlying
performance of each child fell into one of three groups whose cause of these persisting errors likely lies in the constraints
characteristics support the anecdotal evidence that the stages in speech motor control in early development that continue
of later speech development follow a stair-stepping pattern. into the later years (Flipsen, 2003).
Specifically, like Fiona in her “Sahmi” stage, children sta.rt
produce targets that are inaccurate but reliably produced. Dnnclusiona
I_n an effort to push toward accuracy, a period of instability Any parent or grandparent can relate to the fascinating na-
emerges, characterized by greater accuracy but much greater ture of speech development in infancy and early childhood.
variability. About a third of the children in this study were Combined with the catalysts of early language and cognitive
in this stage. Finally, about one-third of the children were in development, it can be astonishing what children say and
a stage with both accuracy and precision, characterized by how they say it. Despite great advances in measuring the ac-
productions that were both correct and less variable. quisition of speech, our understanding of how this complex
skill develops still lacks clarity; it seems that as our knowl-
Vilhan II: Dna5n'I: Go as Planned edge advances, so, too, do our questions. For example. we
The development of speech and the constraints of motor a.re onlybeginning to understand how to identify preschool-
control continue, with refinement and learning occurring aged children who are most at risk for speech sound disor-
throughout childhood and into adolescence (Smith and ders that persist into later childhood. If we could somehow
Zelaznik, 2004). Mastery of all the sounds of American sort through the 15% of 3-year-olds with speech sound er-
English can take up to eight years in a typical, monolingual rors to find the 1% who would face later challenges, we could
child (Edwards, 1992). Speech sound production errors provide intervention that might prevent the later associated
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