Target Selection

Sound Learning vs System Shifting

Traditional vs Phonological Approaches to Target Selection

Traditional• Based on Based on phonetic phonetic

(subordinate)(subordinate) factors factors– developmental norms– stimulability– consistency of error

• AssumptionsAssumptions– motoric basis of sound

learning

– ease of acquisition

– sequential order of acquisition

Phonological• Based on Based on phonemicphonemic

(superordinate)(superordinate) factors factors– phonological complexity– distance metric

• AssumptionsAssumptions– learnability is enhanced

with the greatest amount of change occurring in the least amount of time

Influence of Phonological Complexity on Clinical Management

• Shift in traditional methods of target selection– Traditionally, select sounds that were assumed to be

easiereasier to produce and followed a developmental sequence

– Early, stimulable, and known (inconsistent) sounds

• Currently, new methods of target selection examine the role phonological complexityphonological complexity has on learnability– Specifically, select sounds that are more complex

(later, non-stimulable, and unknown sounds)(later, non-stimulable, and unknown sounds)

– Shift from “sound learning” to “system shifting”

Set-Subset Relationships

TraditionalTraditional• Select simpler targets

that are consistent with child’s current performance and/or developmental norms

• Expose child to “more-of-the same”

Phonological ComplexityPhonological Complexity

X

• Select complex targets that are outside the child’s subset grammar

• To acquire more, a child must be exposed to more

X

A Third Option for Target Selection

• The distance metric represents a different perspective to target selection that doesn’t rely on the dichotomous characterization of targets as early ~ late; stimulable ~ non-stimulable; known ~ unknown, etc.

• RATHER, it is based on the function a particular sound has within a given child’s system– Using phoneme collapses that represent compensatory

strategies developed to accommodate a limited phonetic inventory, we can use a distance metric to select those targets that will result in the greatest amount of change in the least amount of time

Distance Metric (Williams, 2003)

• Select up to 4 different target sounds from one one rule setrule set based on two parameters:

– Maximal Distinction:• select targets that are maximally different from child’s

error in terms of PVM

– Maximal Classification:• select targets from each of the following:

(a) different manner classes

(b) different places of production

(c) different voicing

(d) different linguistic units

Target Selection Using Distance Metric

dkʧfsʃ

stsktrkrkl

1:11 phoneme collapse

Maximal Distinction

clusters

fricatives

affricate

stops Maxi

mal

Class

ifi

cation

t

Targets Selected for AdamTargets Selected for Adamgb stopsdðfvs fricativesz

g ʃʧ affricatesʤgldrfrgr clusterstrkwst

1:18 phoneme collapse

Distance MetricDistance Metric• Systemic/functional characteristics of target

sounds are specific to each child’s own unique system

• Assumes that the importance of target sounds is broader than the characteristics of the sound itself.

• The function of a sound is dependent on the role it plays in a particular child’s unique sound system and therefore it will vary from child to child.

With the distance metric,targets are the salient

“corner puzzle pieces”that help the child

put together the big pictureof the adult sound system

Target Selection:Target Selection:The BIG PictureThe BIG Picture

Comparison ofTarget Selection Approaches

Problems Using Developmental Norms for Target Selection

• Range of differences across developmental norm studies (Prather et al., 1975; Templin, 1957; Sander, 1972; Smit et al, 1990; GFTA, 2000)

• Interpretation of norm charts (developmental progression vs customary production vs mastery)

• Small methodological differences result in large discrepancies in developmental norms

• More recently, look at developmental sequence (Shriberg, 1993)

A Sequence of Development

Early 8 m b j n w d p h

Middle 8 t k g f v ʧ

Late 8 s z l r

Early 8

Middle 8

Late 8

So … do we know when speech sounds develop based on normative studies?

• Probably not!• 2 potential problems with selecting children for

therapy based solely on norms (according to Lof):– Which set of norms can you believe?

– Holding children with SSD to a HIGHER standard• i.e., why are we enrolling children in therapy only when at

least 90% of their peers are producing the sound correctly?

• In essence, we’re not enrolling children until all of the other children have MASTERED the sound

• It seems we’re withholding tx for kids with SSD because they are being held to a higher standard

Practice Selecting Treatment Targets

w w glideglide

l l liquidliquid

ff

h s h s fricativesfricatives

ʃʃ

sw sw clustersclusters

slsl

Practice Selecting Treatment Targets

b b

d d stopsstops

gg

Ø ð Ø ð

v v fricativesfricatives

zz

ʤ ʤ affricateaffricate

Estimates of changes in “Big 10” errors

Phoneme Percentage of children at age 6 with sound in error

% of children at age of typical acquisition still in error

How much change?

/s/ 17% 10% Less than half

/z/ 18% 10% Less than half

// esh 11% 7% Less than half

/ʧ/ 10% 8% Very little

// dja 10% 6% About half

/v/ Age of acquisition <6

/r/ 22% 8% Two-thirds

Vocalic /r/ 18% 4% Three-fourths

// thada 23% 5% Three-fourths

// ev 19% 5% Three-fourths

History of Residual Errors

• From percentage of changes after age 6, it’s clear that improvement only occurs for some phonemes (/r, ɝ, , /

• More than half of the children still in error at age 6 are not going to improve on /s, z, ʃ, ʧ, dja/– In fact, they will get to practice their error for another

year or two if use developmental norms

• In particular, self-correction of /s/ is unlikely; especially if it is a lateralized distortion

Residual Errors

• Need to predict which children with one or more residual errors will correct them without intervention and which ones will not

• Research suggests that children 5-6 years old who are not stimulable for an accurate production will need intervention; those who are stimulable may self-correct.

• Therefore, may want to do short-term intervention with first graders who are not stimulable in order to make them stimulable and then monitor for change– “jump-start” the process and prevent later intervention

Choosing Challenging Targets for Intervention

• How can we get kids to jump to the norms? How can we achieve 2-3 year gains in 1 year?

• Are we applying our resources in the best possible way?

• Nelson, Camarata, & colleagues suggest we need to consider the level of challenge of task

High and Low Challenge Targets

Low Challenge Targets Could run risks:

• hold child below optimal learning rates

• child less interested

• child’s ability is greater than their assessment performance

High Challenge Targets

Could frustration discourage the child?

• YET with rich supports and supportive contexts, child can get RAPID change

• child is positively engaged

• Series of studies by Nelson & colleagues reported that higher challenges were picked up quicker

Writing IEP Goals for Generalization

(after Panagos, 2008)

Traditional Phonological Systemic

Adam will produce the /t/ sound with 90% accuracy over two trials.Adam will produce the /d/ sound with 90% accuracy over two trials.

Adam will suppress alveolar backing at the 90% level of correct articulation in probe lists over two trials.

Adam will expand his word-initial inventory of singletons and clusters by a minimum of 25% on a general speech test by addressing /d,f,ʧ,st/ using a multiple oppositions approach.