Assessing stimulability in toddlers

ELSEVIER

ASSESSING STIMULABILITY IN TODDLERS ANN A. TYLER University of Nevada

This article describes the development and use of a novel, script-based stimulability task for toddlers. A detailed description of the task and procedures for administration is provided. The task assesses stimulability for fricatives, affricates, and liquids in isolation and single words through presentation of toys and objects in a script format during play. Three different levels of cueing are provided to elicit the desired sounds/words. Selected findings from examination of the performance of 10 toddlers with normal speech-language development and 10 with delayed development at an initial assessment and a 6-month reassessment are also described. Results suggest that stimulability testing may be successful with toddlers through the use of a scripted task and that they are more responsive to direct elicitations. Both groups added stimulable sounds; however, there was considerable individual variation with respect to specific sounds added and the addition of nonstimulable sounds as well. Stimulability testing is clinically useful as a dynamic assessment tool for toddlers because it may reveal information regarding a child's speech that is not obtainable with other measures and is also beneficial for individualized intervention planning.

Educational Objectives: The reader will learn the rationale and guidelines for a novel, script-based procedure to test speech sound stimulability in toddlers, as well as preliminary results and clinical implications from its use with toddlers with normal and delayed speech.

INTRODUCTION Stimulability has b e e n used as a clinical procedure to determine if a child is able to revise speech-sound error productions w h e n given a variety o f optimal cues. W h e n applied to the speech system, stimulability has b e e n defined as a phoneme-specific ability that can be predictive of self-correction, generalization, or response to treatment (Carter and Buck, 1958; Deidrich, 1983; F a r q u har, 1961; Powell, Elbert, and D i n n s e n , 1991). A l t h o u g h stimulability results from studies of kindergarten and school-age children are typically interpreted to reflect some degree of predictive validity, "stimulability does not have the predictive significance to determine which children will i m p r o v e with interv e n t i o n and which will improve without it (Shriberg, Kwiatkowski, and Gru-

Address correspondence to Ann A. Tyler, Department of Speech Pathology and Audiology, School of Medicine, University of Nevada, Nell J. Redfield Bldg./152, Rent, NV 89557. E-mail: [email protected] J. COMMUN. DISORD. 29 (1996), 279-297 © 1996 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010

0021-9924/96/$15.00 PII S0021-9924(96)00018-4

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ber, 1994). Stimulability can best be thought of as a form of dynamic assessment. Dynamic assessment is a method of determining the extent to which a child's speech behavior can be advanced by manipulating environmental antecedents and consequences (Olswang and Bain, 1991). Stimulability testing is usually used in the final stages of phonological acquisition, but has not traditionally been used as an assessment tool for children under the .age of 3. With state and local implementation of PL 94-457 and mandated services for toddlers and preschoolers, clinicians are increasingly providing early intervention for children who are at risk for or who have identified speech-language delays and disorders. When clinicians focus on phonology in their early intervention programs, it becomes important to determine sounds that individual children may be ready to acquire. Bleile and Fey (1993) have shown that judicious incorporation of target sounds in known words is an effective method for promoting phonological acquisition, even though intervention'with toddlers typically has its focus on lexical and semantic relation acquisition. The development of stimulability and assessment procedures for use with toddlers is deserving of investigation. The purpose of this article is to provide information about a stimulability task that we developed for use with toddlers and information about its potential for providing useful information for clinicians in assisting toddlers who exhibit delay in expansion of their phonetic inventories. The report that follows consolidates information from two related studies (Maharg, 1994; McKee, 1995). STIMULABILITY TESTING IN TODDLERS:

IS I T F E A S I B L E ? The fact that stimulability has not been used for children under the age of 3 may be due to several reasons. First, children with speech-sound disorders often are not identified as young as toddlerhood. Instead, the reported average age for identification of a developmental phonological disorder is 4;2 (Shriberg and Kwiatkowski, 1994). Yet, children with significant problems in both language and speech, that remain throughout the preschool years, can be identified between 27 and 31 months (Rescorla and Schwartz, 1990). Second, toddlers who are seen for intervention frequently are verbally passive and have limited lexicons. Their depressed language skills relate to the third reason that stimulability data are probably absent; phonological constraints are recognized as operating during early stages of lexical and phonological acquisition. That is, children's phonological systems are limited. Sounds are restricted to certain classes, such as stops and nasals, or to certain positions, and these restrictions can influence lexical development. Children at early ages (1;0 and 1;3) were shown to use words containing phonemes within their repertoires and avoid words containing phonemes outside their repertoires. Schwartz and

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Leonard (1982) showed experimentally that selection and avoidance do operate for very young toddlers. Research has also shown, however, that children's phonological systems undergo rapid changes as a child's lexicon approaches 50 words and phonological constraints seem to decline around this time. Leonard, Schwartz, Folger, and Wilcox (1978) found that children who had acquired 50 words produced consonants in imitated words that they had not attempted in spontaneous speech. Patterns of selection and avoidance that were present in spontaneous speech were not reflected in the children's elicited imitations. Leonard et al. (1978) speculated that after the 50-word period, there may be a rapid relaxation of constraints. Similarly, Leonard, Fey, and Newhoff (1981) studied young children's spontaneous and imitative productions as a function of children's knowledge of words and linguistic development. Once again the children spontaneously imitated words containing target consonants that they had not displayed in spontaneous speech. Further, all of the children were more likely to imitate words containing sounds that were not in their inventories if they had little knowledge of the meaning of the word. Results from a longitudinal study by Dobrich and Scarborough (1992) also support the concept of relaxation of constraints. They followed 12 preschoolers from 2;0 to 5;0 and examined selectional constraints with respect to number of syllables, usage of consonant clusters, and constituent phonemes. They found that although constraints occurred more frequently at age 2;0, at 5;0 the toddlers did not have restricted phonological systems that constrained their word choices. To summarize, results of studies of early phonological selection and avoidance and its relationship to lexical development suggest that such constraints are temporary and do not persist past the 50-word stage of development. Results from these studies also suggest that spontaneous and imitative productions merge as constraints relax and children progress in lexical acquisition. Additionally, phonological characteristics and the use of constraints may differ due to children's unique learning styles (Ferguson, 1976; Vihman and Greenlee, 1987). Once the period of constraints is past, phonological acquisition proceeds at a rapid rate with several sound classes being added between 2;0 and 3;0 years of age. We concluded that toddlers who have passed the 50-word point in lexicai development are likely to imitate words containing sounds that they might not routinely use. Thus, we reasoned that stimulability testing may be possible. We set out to design a task that would engage toddlers and enable us to assess their stimulability.

DEVELOPMENT

OF A NOVEL STIMULABILITY TASK

The stimulability task that we designed was based on a dynamic assessment task (Olswang, Bain, Rosendahl, Oblak and Smith, 1986) in which three dif-

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ferent conditions were used to elicit novel lexical items from language delayed children. Under different conditions, antecedent events varied with directives of cues provided to the child. The conditions that they used were (1) model only the target, (2) model + obstacle condition, and (3) model + elicitation question or statement of the target. Under the model only condition, the clinician provided a model of the target while the child was attending to its corresponding referent. This condition provided an opportunity for spontaneous imitation. Under the model + obstacle condition, a model for a referent that was out of the child's reach or somehow obstructed was provided, thus creating an opportunity for object request. The model + elicitation condition involved modeling the target item and subsequently eliciting that target item (e.g., "Look at the baby. Who is that?"). We decided to present a similar series of successive cues to elicit target sounds and words, beginning with the least direct form and progressing to what would be considered the traditional stimulability format of giving an auditory and visual cue to elicit a target sound in isolation and/or in a word. We designed three different levels of antecedent events to provide stimulation for the child to produce the desired word (see Table 1). Level 1 is termed spontaneous production or imitation. At this level, the clinician presents a model (antecedent event) of the target sound/word three times. The child's response or lack of response is to be recorded. Level 2 is then presented, regardless of the type of response or no response at Level 1. Level 2 is termed question elicitation and the antecedent event is a question (e.g., "What does the bee say?"). The question is presented a minimum of two times. Next, the examiner presents Level 3, regardless of the type of response or no response at Level 2. At Level 3 the child is encouraged to imitate the sound or word following the presentation of an auditory, visual, tactile (AVT) cue (e.g., "Watch my mouth, make a/z/."). Again, the child is given at least two opportunities to respond. A response is considered correct if the target phoneme is produced correctly. If the child gives a response such a s / d o z / f o r "toes," it is considered a correct response because the target phoneme/z/was produced correctly.

Table 1. Levels of Examiner Antecedent Events and Child Responses

Examiner Antecedent

Child Response

Level I

Model only: "The baby says ouch."

Spontaneously produces or imitates ouch

Level II

Question elicitation: "What does the baby say?"

Answers using target ouch

Level III

Auditory, visual, and tactile (AVT): "Watch me, say ouch."

Answers using target ouch

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In addition, we also provided stimulation for sounds that are not likely to be present in toddler inventories, those in the fricative, affricate and liquid classes. Sounds from these classes are being added to phonetic inventories at the ages of 2;0 to 3;3 (Dyson, 1988). These sounds are elicited in isolation and in initial and final positions of mono and bi-syllabic words. In Part I of the protocol, Sounds in Isolation, a total of 12 items are provided to elicit these sounds in isolation - seven fricatives/v, f, 0, s, z, J', 3/, the affricates/tJ', d3/, and the liquids/1, r / a n d / h / . All of these sounds are considered to be mid or later developing sounds (Smit, Hand, Freilinger, Bernthal, and Bird, 1990). The sounds are elicited by associating them with objects that make similar sounds in an onomatopoeic fashion (e,g., "A bee says/zzz/."). Part II of the protocol, Sounds in Words, contains 39 items to elicit each of 11 sounds (11 of those listed above with the exception of/3/) in initial and final positions. Target words were selected from MacArthur Communicative Development Inventory: Words and Gestures (CDI) (Fenson et al. 1991) to provide items that were likely to be present in the lexicon of a toddler. Two words were chosen to obtain each sound in both the initial and final positions. For example, the words f o r / z / a r e zoo, zipper, toes and keys. There are a few exceptions--two words are provided for only initial/r! and initial/h/and only one word for initial/v/. Toddlers are best engaged during play that involves real objects and replica items they observe and use in their everyday routines (Patterson and Westby, 1994). Nelson (1986) hypothesized that routine events are the basis of a young child's cognitive structures. Nelson and others have also shown that children produce more advanced linguistic structures first in routine event contexts. Further, children are not likely to produce a target word unless they are attending to and are interested in its corresponding referent. Thus, we selected a series of routine events as the context for the stimulability tasks and wrote a script on the basis of these events. The children are asked to produce target words for toys, objects, actions, or pictures in the script. Because the words had been selected from a list of common vocabulary items for toddlers, we were able to fit many of them into a sequence of routines enacted with a baby doll. The doll is undressed, washed, dressed, fed, and read a bedtime story. All target words that could not be incorporated into the routines are presented as pictures in the book that is read to the baby. The stimulability protocol is provided in the Appendix. The child's attention is directed to different referents representing target words as the script progresses. For example, after giving the baby a bath, the examiner presents the following sequence of items: The baby's feet are cold. We need to put on hersocks. Now she is ready for her shoes. Next we need to dress the baby. First put on her dress. Does the baby's dress have a zipper?

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I think the baby is thirsty. We had better give her a bottle. Can you give her a bottle? The bottle is full of juice. What kind of juice? Orange. Here is a bowl of her food. The bowl is full of raisins. Give the baby a raisin. The baby says thank you. By using the script the examiner can direct the child's attention to all of the target items in a specified order. The script is flexible enough, however, to allow the examiner to follow the child's lead and slightly change the sequence of events when necessary. This flexibility is the result of the incorporation of familiar events that toddlers typically reenact in their symbolic play. Scoring of the 51-item protocol consists of making tallies of correct, incorrect (based on on-line transcription), and no response at each level of antecedent event. Each response is coded into one of nine categories that represents the kind and accuracy of the response. For each subject, sums of the frequency counts are determined for Parts I and II of the protocol. Stimulability is determined for sounds that were present in the inventory and for those that are not present. Stimulable sounds are defined as those for which there was at least one correct production at any level (i.e., one in four opportunities) and nonstimulable sounds were those scored as incorrect or no response.

Questions w e were interested in determining children's responses to the stimulability task. We had three questions: (1) How would children respond to the different levels of directives in the cueing?, (2) When children were not responsive to items on the protocol, was it because those words were not present in their lexicons?, (3) How did the children's initial stimulability skills relate to their performance 6 months later in regard to the sounds that were subsequently added to their inventories?

Subjects After designing the stimulability task, we administered it to 20 children, I0 with normally developing speech and language and I0 with delayed speech and language (Maharg, 1994). The subjects had been identified by a speechlanguage pathologist at a local children's clinic or the University of Nevada clinic. All of the subjects had achieved at least the 50-word level in their lexical inventories. The group of normally developing children had an average age of 2;0 and the group of children who were speech-language delayed had an average age of 2;9. The majority of the normal subjects were found to have average or above average vocabulary production percentiles (CDI). Two of the subjects

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in the normal group scored below the 40th percentile on vocabulary production and two scored below the 50th percentile on sentence complexity. The delayed group displayed vocabularies below average or below age level. Subjects scored at or below the 10th percentile on either vocabulary or sentence complexity. Those over 30 months of age achieved an age score (referenced to the 50th percentile) that was 10 months or more below their chronological age. Mean length of utterance (MLU) and phonetic inventories were determined for all of the subjects (See Table 2). MLUs ranged from 1.40 to 2.40 with a mean of 1.93 for the normally developing subjects, and from 1.33 to 2.24 with a mean of 1.73 for the delayed subjects. All of the MLUs for the normal subjects were at the predicted level (Miller & Chapman, 1981) or above for their chronological age, while the MLUs for the delayed subjects fell in the range of 1 to 2 standard deviations below the predicted MLU based on chronological age. We found that t-tests performed on the MLUs and ages for the two groups showed no significant difference between the means for the MLUs, but significant difference between the means for age [t (18) = 6.43, p < 001 ]. This indicated that the two groups were at similar language ages, but differed significantly in chronological age. The stimulability task was administered to each of the subjects twice, the second administration 6 months following the first (McKee, 1995). Three subjects from the normal group and two from the delayed group were unavailable for the reassessment. An additional normal subject who fit into the 6 month test-retest pattern was located. A total of 16 subjects (8 in the normally developing group and 8 in the delayed development group) participated in the reassessment. At the time of the reassessment the normally developing group had an average age of 2;8 and MLU of 3.15. The delayed group had an average age of 3;5 and MLU of 3.24. There was no significant difference in the MLUs for the two groups.

Table 2. Number, Mean Age and MLU (with Ranges), and Inventory Size for Normal and Delayed Subject Groups at the Initial Assessment and the Reassessment Initial Assessment Normal

Delayed

Reassessment Normal

Delayed

Subjects

10

10

8

8

Mean age

2;0 1; 10-2;3

2;9 2;4-3;4

2;8 2;3-3;3

3;5 2; 11-4;3

Mean MLU

1.93 1.40-2.40

1.73 1.33-2.24

3. ! 5 2.24-3.72

3.24 1.98-4.60

15

13.2

20

19

Inventory

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Procedures The stimulability task was administered during play sessions lasting approximately 60 rain. with two clinicians and the parent present. Each subject participated in two play sessions approximately 1 week apart at the initial assessment and only one session for the reassessment. The two sessions were necessary initially to familiarize the children with the examiners, the setting and the materials. The sessions were videotaped and both investigators completed on-line transcription of the children's productions.

Analysis and Results How did the children respond to different levels of cueing? Recall that the children were given a model of the target item and an opportunity to spontaneously repeat it. Next they were asked a question to elicit the target item. And following that, they were asked to repeat the target item following the AVT cueing. All of the children in both groups responded more frequently, whether correct or incorrect, at the question and AVT levels than at the spontaneous Level I. This probably occurred because the spontaneous level is indirect and it is not obvious to the children that a response is expected. Further, the normal group had more correct responses and the delayed group had more incorrect responses across all levels of cueing. This reflects the normal group's increased accuracy in comparison with the delayed group. Was the children's lack of response to items in the protocol related to words that were not present in their lexicons? Each child's stimulability protocol from the initial assessment was reviewed to determine which target words received no response. Lexical items for which there were no responses were located on the child's CDI to determine whether or not the parent had indicated them as present in the child's expressive lexicon. The percentage of the words to which the children had not responded and which were not present in their lexicons was relatively small. The average percentage of items that received no response at all and also were not present in the lexicon was 20% for the normally developing group and 27% for the speech-language delayed group. This analysis indicated that, although there were some individual differences, the majority of the subjects were not responsive on the stimulability task apparently due to factors other than avoidance of words not present in their lexicons. What was the relationship between children's stimulability skills and their performance at a 6-month interval following the initial assessment? To examine the relationship between the children's stimulability for a sound at the initial assessment and the presence or absence of the sound at the 6-month reassessment, a 2 × 2 contingency matrix containing two binary variables, stimulability and nonstimulability of a sound at initial assessment, and pres-

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Table 3. Presence or Absence of Sounds at the Reassessment that Were

Stimulable or Nonstimulable at the Initial Assessment Stimulable

Nonstimulable

Present Not present

35 (74%) 12 (26%)

21 (37%) 36 (63%)

Total

47

57

ence or absence of the sound at reassessment was completed for all subjects. The results of each subject's initial assessment were examined to identify sounds from among those not present in their inventory and the presence or absence of these sounds in Part II, Sounds in Words. A sound was considered stimulable if it occurred at least one time at any level (i.e., one in four opportunities). A sound was considered nonstimulable if it was scored as incorrect or no response. On reassessment a sound was considered present if it was correctly produced in at least one target item at two or more different levels on the stimulability protocol, and also appeared in other words either from spontaneous speech or the protocol. For example for one subject (D3) t h e / J ' / w a s not present in the subject's initial inventory but was produced two times at the AVT level during the initial assessment. At reassessment the subject produced /J'/one time at the spontaneous level, one time at the A V T level, and also in spontaneous speech. Both groups added both stimulable and nonstimulable sounds; however, there was considerable individual variation with respect to the specific sounds that they added. O f the 57 nonstimulable sounds at the initial assessment, 21 (37%) were present at reassessment and 36 (63%) were not present (See Table 3). Of the 47 sounds that were stimulable at the initial assessment, 35 (74%) were present at reassessment and 12 (26%) were not present. Percentages of sounds that were stimulable at the initial assessment and subsequently present at reassessment were also determined for comparison of

Table 4. Percentage of Possible Stimulable or Nonstimulable Sounds from the Initial Assessment that Were Subsequently Present at the Reassessment for Both Groups

Stimulable Normal Delayed Nonstimulable Normal Delayed

Correct/ Possible

Percentage

22/26 13/21

85 62

9/21 12/36

43 33

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the performance of the two groups (Table 4). The normally developing group acquired 85% of the stimulable sounds, whereas the delayed group acquired 62%. For nonstimulable sounds the normal group acquired 43% and the delayed group acquired 33%. Thus, the normal g r o u p ' s performance was better than that of the delayed group for both stimulable and nonstimulable sounds. The normal group added almost twice as m a n y stimulable sounds as nonstimulable sounds, but the delayed group added about the same amounts of stimulable sounds a.s nonstimulable sounds. It appears that the delayed g r o u p ' s phonological acquisition was at a slower pace than that of the normal group. Table 5 shows the sounds not present in the subject's inventories at the initial assessment and those present at the reassessment, according to stimulability status. Examination of these sounds shows individual variation with respect to stimulability status for affricates, later developing fricatives, and liquids, the sounds not present at T1 for the majority of the subjects. The normally developing subjects often had similar amounts of stimulable and nonstimulable sounds from among those that were absent. In contrast, the delayed group were either stimulable or nonstimulable for the majority of the sounds absent from their inventories. L o f (1994) also found that children who were stimulable had better productions for all errors, whereas children who were not stimulable generally had poorer productions of all errors.

Table 5. Sounds that Were Not Present at the Initial Assessment (T1) and Were Subsequently Present at the Reassessment (T2), According to Stimulability Status, for All Subjects Sounds not Present at T1 Subject

Stimulable

Sounds Present at T2

Nonstimulable

Stimulable

Nonstimulable

N1 N3 N5 N6 N7 N8 N9 N11

/v, r/ /0, f, tJ', d3, 1/ -/0, v, L tJ', d3, 1, r/ /0, v, s, z, .f, t J"d3, r/ - /0, z, tS, d3/ /v, 1, r/ /0, t f, dS/ -/5, tJ', d3/ /0, 1/ /v, z, f, 1, r/ /0, t f, ds/ /tJ'/ /ds/

/v/ -/0, v, s, z, .f, tJ'/ /z, tJ', ds/ /0, tJ', dS/ /S, tJ', d3/ /v, z, J', 1, r/ /tS/

-/0, 1/ -/1, r/ -/1/ /0, tJ', ds/ /d3/

D1 D1 D3 D4 D6 D7 D8 D9

/f, z, J'/ /ds/ /v, s, z, f, d3/ -/1/ /0, f, v, S, tf, d3, l, h/ /v, d3/ /0/

/f, z, J'/ -/s, z, J', ds/ --

/v/ -/tJ'/ /s, J'/ /s, z, J', tJ', d 3 / /r/ -/J'/

/0, v, t f, d3, 1, r/ /0, f, s, z, J', tJ', 1, r, h/ /0, if/ /0, s, z, J', 1/ /0, v, s, z, J', tJ', d3/ /r/ /1/ /f, v, J~, d3, 1/

--

/0, f, d3, h/ /v, d3/ --

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At reassessment, there was also considerable individual variation. Several subjects in the delayed group added more nonstimulable than stimulable sounds. This rarely occurred in the normal group where most children added more stimulable than nonstimulable sounds. Both groups added the following sounds/0, v, s, z, J', tJ', d3, r, h/. The only differences for the normal subjects were the additions of/1/and the delayed subjects' addition of/f/.

CLINICAL IMPLICATIONS The preliminary results of our studies show that stimulability testing can be successfully used to assess toddlers' productions of mid- to later-developing sounds. We believe that our success was primarily due to the use of a script to focus the attention of toddlers. The script not only contained familiar words to sample certain sounds, but also familiar routines enacted with toys and objects. Second, all the toddlers we tested seemed to be sensitive to the levels of cueing in the task. They were not responsive to the spontaneous condition that was indirect and involved no request or elicitation of the target item. In conWast, they were more likely to respond when asked a question or given an auditory, visual, and tactile cue for the target. For clinical purposes, we recommend eliminating the spontaneous level of cueing from the stimulability task. This would shorten the length of time needed to administer the task. Finally, our preliminary results lead us to suggest that the stimulability task may best be used as a form of dynamic assessment to assist in decisions regarding target sounds for an intervention program. Sounds that were stimulable and subsequently acquired differed for individual children; thus, stimulability testing can provide useful information for selecting target sounds in individualized intervention programming. Early speech-language intervention with toddlers typically has a focus on language. Within this focus, however, it is quite desirable to incorporate goals for the phonological system, because it has been reported that phonology is a linguistic domain that may lag behind others in subsequent years (Tyler, 1992; Whitehurst, Fischel, Lonigan, Valdez-Menchaca, Arnold, & Smith, 1991). When they are first diagnosed with a speech-language impairment, toddlers' lexical and phonological systems are more often than not commensurate, although delayed (Tyler, 1992). This means that their phonological systems--phonetic inventory and error patterns--are more typical than atypical of what would be expected on the basis of the overall level of language development. For example, the present group of delayed subjects had an average inventory of 13 sounds and an MLU of 1.73. These gross averages would suggest that the two systems are at similar developmental levels (Miller, 1981: Stoel-Gammon, 1985). When phonology is clearly not deviant, but nevertheless is delayed with respect to chronological age, it deserves at least indirect attention and monitoring. Phonology can be enhanced through an intervention program and the most reasonable basis

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for goal development is from stimulability data as they relate to the child's existing system. There are also children who have clearly disordered phonology when they are first seen as toddlers. It is even more critical that stimulability data be used when phonology is an obvious domain for intervention, because children with disordered phonology are more likely to have unique characteristics to their systems. If phonology is to be a focus with toddlers, it is usually recommended that expansion of the phonetic inventory and syllable structures be goals and that stimulable sounds be the target of intervention (Bleile, 1995). Our results would also suggest, however, that children with speech-language disorders are almost as likely to acquire nonstimulable sounds. Further, Poweli et al. (1991) showed that treatment of nonstimulable sounds was associated with generalization to stimulable sounds, whereas treatment of stimulable sounds facilitated limited generalization. We recommend selecting stimulable and nonstimulable sounds as targets based on a child's existing phonetic inventory. A least-knowledge method should be followed in selecting intervention targets whereby sounds differ from the child's existing abilities by multiple features (Elbert & Gierut, 1986; Gierut, Elbert, & Dinnsen, 1987). Both stimulable and nonstimulable targets should differ from sounds already present in a child's inventory by several features, if possible. This will increase the likelihood of generalization across the system, so that untrained sounds sharing the features of intervention targets may also be acquired. For example, D3 in the present study had an inventory of stops, liquids, nasals, and one fricative /f/. The stimulable sound/z/might be a target and the nonstimulable sound /tJ'/might be a target. Each of these sounds differs from sounds in the child's initial inventory in critical ways. T h e / z / i s another fricative, but introduces voicing and the alveolar place of articulation in the fricative class;/tj'/differs from existing sounds and classes by its delayed release feature. Once stimulable and nonstimulable target sounds are selected, they can be presented to the child using different methods within the more general language intervention program. Stimulable sounds can be incorporated in familiar words and presented through intensive modeling (i.e., focused stimulation), but not directly elicited from the child (Camarata, 1995; Kelman & Edwards, 1994). In other words, the child is exposed to an increased number of occurrences of the target sound, but he/she is never required to produce it as a response to the clinician. Developmentally appropriate activities are designed specifically around the target words. In our example of the stimulable target/z/, an activity involving a zoo or Noah's ark in which animals in pairs were presented and manipulated could be designed. In this manner final/z/as a plural could be modeled extensively. The nonstimulable sound/tJ'/, in contrast, can be presented using more direct teaching techniques that involve eliciting responses in specific words and correcting or reinforcing them. Procedures focusing on sound production and

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perception can be incorporated within a more general language intervention program without being drill oriented. For example, sound production activities can be incorporated in games and routines designed around key lexical items that are selected as examplars for the target sound. Selected lexical items should have simple syllable structures and be common in the lexicons of young children. Successful activities often involve using language in a pragmatic context that obligates the child be given an assertive role involving the communicative functions of requesting action, requesting objects, or directing attention. In our example for subject D3, the target words for/tj'/might be chips, chase, cheese, chew, and check. One activity for the target word chase could involve the child and clinician taking turns directing each other to chase specific play figures. In another activity, the clinician and client could take turns presenting the choice of chips or cheese during a pretend snack activity involving an array of stuffed animals or dolls. The example provided here suggests that stimulable and nonstimulable sounds be selected as targets to expand the phonetic inventory within a larger language intervention program, but that the two types of targets be presented to the child using different teaching techniques--direct for nonstimulable sounds and indirect for stimulable sounds. The rationale for targeting both types of sounds stems from the 6-month reassessment results reported here, as well as research showing that children generalized correct production to a greater number of untreated sounds when nonstimulable sounds were targets (Powell et al., 1991). It would be especially important that toddlers with obvious phonological impairments have both stimulable and nonstimulable intervention targets. For toddlers with no obvious phonological impairment, but a specific expressive language delay with commensurate phonology, stimulable sounds only could be targeted and treated indirectly if the intervention focus is primarily on language. To summarize, this chapter reported on the design and implementation of a novel, script-based stimulability task for toddlers. Preliminary findings from the use of our stimulability task with toddlers with normal and delayed development showed that the script format was successful in focusing toddlers' attention and facilitating their Successful completion of the task. Both groups were more responsive, whether correct or incorrect, at the more direct (question and AVT) levels and less responsive at the spontaneous level of cueing. Further, we found that a lack of responsiveness was not generally due to the children's lack of knowledge of the lexical items. Finally, both toddler groups added stimulable sounds; however, they added nonstimulable sounds as well. The delayed group added a smaller percentage of stimulable sounds over the 6-month period than did the normal group. Stimulability testing is clinically useful as a dynamic assessment tool for toddlers because it may reveal information regarding a child's speech that is not obtainable with other measures and is also beneficial for individualized intervention planning. Suggestions

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were provided for selecting both stimulable and nonstimulable sounds as possible targets to expand a toddler's phonetic inventory and presenting those targets with differing teaching techniques within a larger language intervention program.

REFERENCES Bleile, K.M. (1995). Manual of articulation and phonological disorders. San Diego, CA: Singular Publishing Group. Bleile, K.M., & Fey, M. (1993, November). Issues and methods in providing articulatory and phonological services to infants and toddlers. Miniseminar presented at the Annual Convention of the American Speech-LanguageHearing Association, Anaheim, CA. Camarata, S. (1995). A rationale for naturalistic speech intelligibility intervention. In M. Fey, J. Windsor, & S. Warren (Eds.), Language intervention preschool through the elementary years (pp. 63-84). Baltimore, MD: Paul H. Brookes Publishing. Carter, E., & Buck, M. (1958). Prognostic testing for functional articulation disorders among children in the first grade. Journal of Speech and Hearing Disorders, 23, 124-133. Diedrich, W., (1983). Stimulability and articulation disorders. Seminars in Speech and Language, 4, 297-311. Dobrich, W., & Scarborough, H.S. (1992). Phonological characteristics of words young children try to say. Journal of Child Language, 19, 597-616. Dyson, A.T. (1988). Phonetic inventories of 2- and 3-year-old children. Journal of Speech and Hearing Disorders, 53, 89-93. Elbert, M., & Gierut, J.A. (1986). Handbook of clinical phonology: Approaches to assessment and treatment. San Diego: College-Hill. Farquhar, M.S. (1961). Prognostic value of imitative and auditory discrimination tests. Journal of Speech and Hearing Disorders, 26, 342-347. Fenson, L., Dale, P.S., Resnick, J.S., Thai, D., Bates, E., Hartung, J.P., Pethick, S., & Reilly, J.S. (1991 ). The MacArthur Communicative Development Inventories. San Diego: San Diego State University. Ferguson, C.A. (1976). Learning to pronounce: The earliest stages of phonological development in the child. Papers and Reports on Child Language Development, 11, 1-27. Gierut, J.A., Elbert, M., & Dinnsen, D.A. (1987). A functional analysis of

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phonological knowledge and generalization learning in misarticulating children. Journal of Speech and Hearing Research, 30, 462-479. Kelman, M., & Edwards, M.L. (1994). PHONOGROUP: A Practical Guide for Enhancing Phonological Remediation. Eau Claire, WI: Thinking Publications. Leonard, L.B., Fey, M.E., & Newhoff, M. (1981). Phonological considerations in children's early imitative and spontaneous speech. Journal of Psycholinguistic Research, 10, 123-133. Leonard, L.B., Schwartz, R.G., Folger, M., & Wilcox, M. (1978). Some aspects of child phonology in imitative and spontaneous speech. Journal of Child Language, 5, 430-417. Lof, G.L. (1994, November). Factors associated with speech-sound stimulability. Poster presented at the Annual Convention of the American SpeechLanguage and Hearing Association, New Orleans, LS. Maharg, M.M. (1994). Toddlers with normal and delayed language: Comparison ofstimulability performance. Unpublished Master's thesis, University of Nevada, Reno. McKee, A. (1995). Toddlers with normal and delayed language: Reassessment ofstimulability performance. Unpublished Master's thesis, University of Nevada, Reno. Miller, J., & Chapman, R. (1981). The relations between age and mean length of utterance in morphemes. Journal of Speech and Hearing Research, 24, 154-161. Nelson, K. (1986). Event knowledge: Structure and function in development. Hillsdale, NJ: Erlbaum. Olswang, L.B., & Bain, B.A. (1991). When to recommend intervention. Language, Speech, and Hearing Services in Schools, 22,255-263. Olswang, L.B., Bain, B.A., Rosendahl, P.D., Oblak, S.B., & Smith, A.E. (1986). Language learning: Moving performance from a context-dependent to -independent state. Child Language Teaching and Therapy, 2, 180-210. Patterson, J., & Westby, C. (1994). The development of play. In W. Haynes and B. Shulman (Eds.), Communication development. Foundations, processes, and clinical applications. (pp. 135-162). Englewood Cliffs, NJ: Prentice-Hall. Powell, T.W., Elbert, M., & Dinnsen, D.A. (1991). Stimulability as a factor in the phonoPogical generalization of misarticulation in preschool children. Journal of Speech and Hearing Research, 34, 1318-1328.

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Rescorla, L., & Schwartz, E. (1990). Outcome of toddlers with specific expressive language delay. Appliedpsycholinguistics, 11,393-407. Schwartz, R.G., & Leonard, L.B. (1982). Do children pick and choose? An examination of phonological selection and avoidance in early lexical acquisition. Journal of Child Language, 9, 319-336. Shriberg, L.D., & Kwiatkowski, J. (1994). Developmental phonological disorders. I. A clinical profile. Journal of Speech and Hearing Research, 37, 1100--1126. Shriberg, L.D., Kwiatkowski, J., & Gruber, F.A. (1994). Developmental phonological disorders. II. Short-term speech-sound normalization. Journal of Speech and Hearing Research, 37, 1127-1150. Smit, A.B., Hand, L., Freilinger, J.J., Bernthal, J.E., Bird, A. (1990). The Iowa articulation norms project and its Nebraska replication. Journal of Speech and Hearing Disorders, 55, 779-798. Stoel-Gammon, C. (1985). Phonetic inventories, 15-24 months: A longitudinal study. Journal of Speech and Hearing Research, 28, 505-512. Tyler, A.A. (1992). Profiles of the relationship between phonology and language in late talkers. Child Language Teaching and Therapy, 8, 246-264. Vihman, M.M., & Greenlee, M. (1987). Individual differences in phonological development: Ages one and three years. Journal of Speech and Hearing Research, 30, 503-521. Whitehurst, G.J., Fischel, J., Lonigan, C., Valdez-Menchaca, M., Arnold, D., & Smith, M. (1991). Treatment of early expressive language delay: If, when, and how. Topics in Language Disorders, 11, 55-68. Appendix. Phonology Stimulatibility Protocol (Maharg, 1994) DIRECTIONS: Record the child's response on each line, whether correct or incorrect. If a correct response occurs at any level, automatically go to the next stimulus item. LevellI: QuestionElicitation.State question given in script to elicit sound/word. Give the child at least 2 opportunities to respond. If correct response: record and move onto next item. If no response or incorrect response: record and move onto AVT imitation. Level 111:Auditory, visual,and tactile (AVT) imitatiorLGiving all three cues, present at least two opportunities for the child to produce the sound/word. For example, "Watch me, make a/v/" while touching chin. Record response and move to next item on the protocol. continued

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Appendix. Continued PART H The target word is in bold. The target sound appears at the end of each phrase. If the target sound is produced correctly, the response is considered correct. Remember, at least two opportunities at Levels 2 and 3. The examiner presents the items to the child in the order listed and reads the script. We are going to play with a baby. Do you like babies? This is a nice baby. We are going to give the baby a bath, we need to take his/her clothes off. Off /f/ "What are you doing to the baby's clothes?" AVT Imitation (Point to band-aid on the baby's knee). The baby has a boo-boo (owie), she says'ouch! /tS/ "What does the baby say?" AVT Imitation Do you want to help me wash the baby? Wash. /J'/ "What are you doing to the baby?" AVT Imitation We need to use a towel and some soap. Soap. /s/ "What are you using?" AVT Imitation What are these, the baby's toes? Toes. /z/ "What are those?" AVT Imitation And these are the baby's fingers? Finger. /f/ "What are those?" AVT Imitation This is the baby's hair. Hair. /h/ "What is this?" AVT Imitation Where are the baby's cheeks? Pinch the baby's cheek. Cheek. /tJ'/ "What are you pinching?" AVT Imitation What is this? It's the baby's mouth. Mouth. /0/ "What is that?" AVT Imitation Give the baby a kiss. Kiss. /s/ "What did you give the baby?" AVT Imitation Does the baby have teeth? Teeth. /0/ "What are those?" AVT Imitation The baby's feet are cold, we need to put on her goeks. Socks. /s/ "What are you putting on her feet?" AVT Imitation Now she is ready for her shoes. Shoes. /J'/ "What are you putting on her feet?" AVT Imitation continued

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Appendix. Continued Next we need to dress the baby. First put on her dress. Does the baby's dress have a zipper7 Zipper. "What is that?" AWl" Imitation I think the baby is thirsty. We had better give her a bottle. She's thirsty.

Thirsty. "What is she?" AVT Imitation Can you give her the bottle? Give. "What did you do?" AVT Imitation The bottle is full of juice. Juice. "What's in the bottle?" AVT Imitation What kind of juice? Orange. "What kind of juice?" AVT Imitation Here is a bowl for her food. Bowl. "What is this?" AVT Imitation The bowl is full of raisins. Raisins. "What's in the bowl?" AVT Imitation Give the baby a raisin. The baby says thank you. Thank you. "what did the baby say?" AVT Imitation Here is another dish for her food. Dish. "what is this?" AVT Imitation Be careful it is hot. Hot. "The dish i s . . . 7 " AVT Imitation The baby is getting tired. We need to read her a bedtime story. Here's a picture book, let's look. Look. "What are you doing?" AVT Imitation Here's a family going for a drive. Drive. "What are they doing in the car?" AVT Imitation They use keys to tum on the car. Keys. "What are these?" AVT Imitation Now they are backing out of the garage. Garage. "What are they backing out of?." AVT Imitation They want to listen to music. They turn on the radio. Radio. "What is this?"

/z/

/0/ /v/

/d3/

/d3/

/1/

/r/

/0/

/J'/

/h/

/1/

/v/

/z/

/d3/

/r/ continued

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Appendix. Continued AVT Imitation They are going to the zoo. Zoo. "Where are they going?" AVT Imitation They see a horse. Horse. "What do they see?' AVT Imitation The horse is about to j u m p over a fence. J u m p . " w h a t is the horse going to do?" AVT Imitation And here's a dog that says woof. Woof. " w h a t does the dog say?" AVT Imitation This is a picture of a mama sheep. Sheep. "This is a m a m a . " AVT Imitation and her baby lamb. Lamb. "This is the b a b y . . . " AVT Imitation Here's a boy holding a ball. Ball. " w h a t is the boy holding?" AVT Imitation This is a colorful fish. Fish. " w h a t is this?" AVT Imitation The last picture is a chicken. Chicken. "What is this?" AVT Imitation Oh, look at the watch. It's about time for the baby to go to bed. Watch. " w h a t is this?" AVT Imitation Good-night baby. Oh, look at the mess we made. We had better v a c u u m it up. Vacuum. " w h a t is this?" AVT Imitation Comments

/z/

/s/

/d3/

/f/

/f/ /1/

/l/

/f/

/tJ'/

/tJ'/

/v/