the inference of speech perception in the ...

THE INFERENCE OF SPEECH PERCEPTION IN THE PHONOLOGICALLY DISORDERED C H I L D . P A R T I: A RATIONALE, SOME CRITERIA, THE CONVENTIONAL TESTS

John L. Locke Institute for Child Behavior and Development, Champaign, Illinois

This paper considers the rationale and presents some criteria for assessing the speech perception of children with disorders at the phonological level of language. An examination of conventional test procedures suggests that none is useful in identifying clinically relevant perceptual disorders. However, readers are encouraged to inspect Part II (Locke, 1980), which describes procedures with more clinical promise.

O u r concern in this p a p e r is a child whose speech is quite unlike his parents' a n d that o f his peers. Clinicians have found his auditory sensitivity to be normal. At some point in the child's therapy, however, someone will wonder about, test, perhaps even try to change his perception o f speech. W h e t h e r this can help the child and how one ought to do the testing are questions to be considered in the succeeding pages. We also will examine whether it makes clinical sense to assess perception with conventional procedures.

ASSESSING

SPEECH

PERCEPTION

A Rationale from the Past T h e child in question is not p r o d u c i n g the expected or most desirable set o f linguistic sounds. In therapy, one might do something about the way he emits these sounds, that is, help the child use his vocal tract differently. Some of the implements o f the clinic, the m i r r o r a n d the tongue depressor, are evidence o f this approach. T h e r e are, as well, the methods o f the clinician who manipulates the child's oral structures or uses phonetic context to elicit or discover correct productions. These are production techniques. T h e y a p p e a r motivated by principle in some cases, by pragmatism in others. A child with a production disorder is given production training, and what could be more logical? In fact, however, much o f his therapy may be perceptual. Instead o f attacking the child's i m p r o p e r articulatory responses, perception training, circuitously, aims at the aural-phonetic stimulus to those responses. T o my knowledge, a rationale for this has never been formally specified. I f there were one, it probably would look like this: 431

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1. The child is not producing the right phonological segments because he does not know how the right segments sound (this implies that the child has an efficient articulatory system that is faithfully replicating the wrong sounds); 2. Perception training can teach the child what the right segments sound like; 3. When the child has learned how the right segments sound, he will begin to produce those segments correctly (this happens "automatically"). T h e problem with this logic is its supposition of "facts" that need not be supposed-that is, are verifiable--and that may turn out to be non-facts in the end.

A Little Scrutiny Looking at how the child's training actually is conducted, one may discover that it is not oriented purely toward either production or perception. Instead, the clinician may be seen physically manipulating the lips and tongue of the child who says [f] in favor o f / 0 / b u t may be heard bombarding him with [a~:]s when the child improperly produces the less palpable tokens of/r/. To the extent that it is applied in this selective manner, one might conclude that unlike production techniques, perception training is done neither by principle nor pragmatism but by default. Were it possible to determine whether the child misperceives speech in much the same way that he misproduces it, one still would not know if perceptual failure were motivating or maintaining the child's production errors, in fact, there is reason at present to believe that the causality might as logically work in the opposite direction. Even if the child does have a perception disorder, the most efficient solution to both problems might well be production training. There is evidence, after all, that articulatory training benefits both production and perception, whereas perception training is likely to benefit perception only (Williams and McReynolds, 1975). Since intact perception is not sufficient for normal production, in the wake of perception training the clinician would be left with the need to begin production work or the child would be left with his disorder of speech. Why, then, assess perception? Why, once assessed, attempt to change it? Perhaps the best answer at this time is that we should worry about neither the assessment nor the treatment of speech perception disorders. However, much of our thinking on this issue is weakened by the fact that efficient perception measures have not been in general use. Because perceptual questions, historically, have not properly been asked in the laboratory, it is not obvious that perceptual questions currently should be answered in the clinic.

A Rationale for the Present Is it not reasonable, however, in serving the child who fails to produce differently the functional units of phonology, to ask if he is aware that there are different targets that could be aimed at? Does the child know that his phonetic forms are not those o f the adult community? T h e procedures with which one may infer the child's perceptual ability are our only good index to the inventory and organization of the child's receptive phonology (Locke, 1979a). Not only does perceptual evidence permit a more complete understanding o f the child's phonological system; it also clarifies the broad distinction between articulatory and systemic disorder--hence the extent to which the problem is one of linguistic rules as opposed to production or perception deficiencies (Braine, 1976). It appears that there may in many cases be little justification for not assessing the

LOCKE: Inference of Speech Perception, Part I 433 child's perception of speech. T o do so in a clinically meaningful way, however, one needs guidelines for selecting or designing the procedures.

Preliminary Assumptions While perception is " o f ' something, only the "something" may be observed. T h e processes o f perception are inescapably private. T h e r e is, consequently, no way perception can be tested. At best, one can put the child on a task in which his responses to his perceptions can be witnessed and infer from the entire pattern o f activity the child's perceptions. To assess p h o n e m e perception, something phonetic must go in the ear of the subject, reach and reside briefly in the brain, and r e t u r n in translated form by way of the subject's response. We are assuming here that the salient features o f the stimulus faithfully enter the ear and brain and that the subject's r e p o r t represents his reaction to and j u d g m e n t about the stimulus. One never will know what was perceived, only that Sensory Event #1 and Sensory Event #2 elicited different responses. Since any two speech sounds may differ by a variety of phonetic cues (Lisker, 1978), it is possible that the listener discriminates on the basis o f a cue or set o f cues the clinician does not have in mind, and may not even know about. T h e clinician may be relieved to observe consistent discrimination o f / t a / a n d / d a / , but the child could have predicated his decisions on the f u n d a m e n t a l frequency o f the vowel, which does not need to be replicated in his production pattern, rather than the aspiration values o f the stops, which do. Therefore, the child's consistently different responses to Phonemes A and B cannot be taken to mean that he perceives A and B correctly or in a way sufficient for their correct production. On the other hand, the subject's failure to r e s p o n d differentially does not necessarily mean that he detects no difference between the speech stimuli. T h e r e are reasons why it would be just as logical to assume that the stimuli were correctly perceived but that the child failed to act on his correct perceptions so as to reveal them in his overt behavior. T h e child, prior tO his perceptual experience, must d e t e r m i n e which o f various depths and types of analysis he is expected to p e r f o r m . Following his p e r c e p t u a l experience, the child must decide whether the cues are o f sufficient magnitude, or o f the right type, to indicate this in his response, in addition, after making the j u d g m e n t , the child must recall or devise the means of r e s p o n d i n g requested by the examiner or implied by the structure of the task.

Assessment Criteria In the speech clinic, questions about p h o n e m e perception usually are inquiries into production-relevant perceptual behavior. Since the child has a production disorder, the focus o f the perception task would have to be the perception o f sounds he misproduces. W h e n a child does not p r o d u c e a s o u n d correctly, h e - - i n the mind o f the listener--does something instead. T h e child may distort it, producing a phonetic error. In this case the child often reveals his knowledge o f which p h o n e m e is a p p r o p r i ate because he articulates a representation o f that phoneme. A distorted Is] still-usually--is a form of/s/. From the child's production behavior there is little reason to suspect that he perceives one p h o n e m e as another. A more likely possibility is a phonemic error, in which the child's deviation is heard as another English p h o n e m e (and, therefore, is classified as a substitution) or appears to comprise an empty slot

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(and is, therefore, classified as an omission, though many of these slots may be subphonemically filled; Bernthal and Weiner, 1976). As argued elsewhere (Locke and Goldstein, 1971), if there is a functional relationship between p h o n e m e production and perception, • . . children [who] p r o d u c e / t / f o r / k / . . , should perceive/ff for/k/. If the discrimination task item is/g-k/they should get it right because, although they have "trouble" producing/k/their difficulty does not run in the direction of/g/. If/k/sounded like /g/, presumably some of the time they would make/g/for/k/. (p. 107) If, that is, they can say /g/. Consequently, the perceptual question should be as selective as the production question. T h e r e would be no point in sampling all the major contrasts, or testing every sound in relation to some other sound, because the child does not have difficulty in p r o d u c i n g all sounds. What clinical action should be taken if the child says [w] f o r / r / b u t cannot d i s c r i m i n a t e / t / f r o m / k / ? i f the child says /t/ and Ik/ correctly, he, logically, must be able to tell them apart. T h e child's differential productions indicate his capability o f differential reception. (There are some interesting exceptions to this but it would be too distracting to treat them here.) On the other hand, suppose the child gets t h e / t / - / k / c o n t r a s t right; isn't this something one might already have a d d u c e d from his production data? I f perception testing is for a clinical purpose, that p u r p o s e is to modify output behavior, and in the case of/t/ a n d / k / t h e r e would be nothing to modify. O u r first criterion, then, is that the assessment procedure should (1) examine the child's perception o f replaced sounds in relation to replacing sounds. T h e problem is complicated, however, by the fact that articulation is contextsensitive. A child who says A in place of B in one phonetic environment does not necessarily do that in another phonetic environment. In 30 /if-defective children, Curtis a n d Hardy (1959) f o u n d the accuracy o f / r / production to vary, over 43 different phonetic contexts, from 3% correct f o r / f r / t o 49% f o r / p r / . In 10/s/-defective children, Mazza, Schuckers, and Daniloff (1979) f o u n d the accuracy o f / s / p r o d u c t i o n to vary, over 48 different phonetic environments, from 3% correct f o r / n s n i / t o 90% correct for/pska/. If we cannot observe a g r e e m e n t between the production o f a particular p h o n e m e in one context with the production o f that same p h o n e m e in a different context, how could we possibly expect agreement between production and perception when they involve different phonetic environments? Assume that a child articulates [w] in place o f / r / o n an articulation test in which he must name a picture of a rabbit. T h e n the child is given a test o f his speech perception in which he must determine whether wing and ring are different. I f the child decides that they are different, did he do this because (a) [w] and [r], in all cases, are t o h i m members o f two phonemic classes or (b) he says ring and wing correctly, hence his production and perception are in perfect agreement in that context. Whether the child could discriminate wabbit-rabbit, that is, the contrast that he collapses in production, would be unknown, That context, however, is the one that gives rise to our clinical concern. We argue, then, that o u r task must (2) observe the same phonemes in identical phonetic environments in production and perception. This means, obviously, that the items for the perception task cannot be selected until the child's speech production errors have been identified; the "test" can be little more than a series of empty blanks. When the child commits errors on the articulation test, he unwittingly fills these blanks, creating by himself and for himself an a p p r o p r i a t e test o f his phoneme perception. T h e r e is an additional benefit: If the child knew the words well enough to speak them earlier, in the production task, the

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words will not be unfamiliar when they r e a p p e a r in the perception task. T h e only alternative, if it reasonably could be considered one, would be to design a task in which every conceivable speech e r r o r appeared. This task would contain several t h o u s a n d items. Even if the test were r e a s o n a b l e , - h o w e v e r , and c o n t a i n e d not thousands o f items but, say, 50, doesn't that m e a n - - f o r the child with five phonemic substitutions--that 45 of the 50 are irrelevant to him and, therefore, irrelevant to his clinician? A n o t h e r of our assumptions is that p e r c e p t i o n findings are meaningless if the perceiver never gives any evidence o f discriminative responding. One conventional discrimination test, the Auditory Discrimination Test (Wepman, 1973), tries to account for this; the test is invalid if the child does not get most o f the "same" items correct (presumably because the expected e r r o r in discrimination testing is unidirectional, that is, a subject may think two different items are the same but never that two identical items are different). However, if the child calls every pair same, the behavior is counted. Is the child saying same because he (a) is attending, understands the instructors, but fails to detect differences in any of the pairs or (b) is not attending, does not u n d e r s t a n d the instructions, or wishes he were somewhere else? T h e temptation might be to provide the child with an entirely different set of-items just to make this determination, as discrimination tasks often do. However, that would control only for the child's u n d e r s t a n d i n g o f task instructions, not for the execution o f those instructions with reference to the relevant phonetic contrast. For example, assume the child says [w] in place o f / r / a n d that we wish to know whether he can discriminate between these two sounds. I f the child reports a difference bet w e e n / r / a n d a perceptually similar control sound he never says in place of it, such as /1/, the child probably is sufficiently trained; cooperative, and attentive. However, if the child is given i n d e p e n d e n t control items, like/t/-/s/, correct r e s p o n d i n g would not indicate he is u p to the real task, discriminating the replaced sound from an unreplacing alternative. T h e reason is that the perceptual distance b e t w e e n / w / and /r/ may be less, even'for the normal talker-perceiver, than it is for/t/-/s/. Mild inattention could survive this grosser contrast but not the more subtle one, and the child would miss the crucial contrast but for reasons not straightforwardly perceptual. This suggests a third design characteristic, that the task must (3) permit a comparison o f the child's p e r f o r m a n c e on target and replacing sounds with discrimination of target and perceptually similar control sounds. However a child perceives/r/, if he p r o d u c e s / w / f o r / r / , he does not act as i f / r / i s / f / o r / k / o r some other p h o n e m e he never says in its place. T h e question is whether the child thinks it i s / w / o r an acceptable variant of/w/. If one uses in a control context an item with which /r/ should never be confused, one would not want to select indiscriminately any sound. T h e control item cannot serve much o f a controlling function if it is so perceptually distant from the target that it need not be carefully attended to for a correct decision. T h e misperception data from children and adults never have shown t h a t / r / i s perceptually confusable with/k/. T o p a i r / r / w i t h / k / , then, seeking a j u d g m e n t as to whether king differs markedly from ring, is-to request a decision so simple that the subject is excused from this otherwise difficult task just to keep the validation alive. An additional weakness here is the potential for decreasing the relative psychological distance between the crucial items. Relative to king-ring, wing and ring really are quite similar. If the control item is ling, though, which perception studies show to be confusable with ring (or at least/1/with/r/), the control item performance will at least be based on a decision of roughly comparable difficulty (the child's production behavior notwithstanding).

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The Child's Internal Representations. T h o u g h discrimination tests require that an individual "tell two things apart," the two things need not be in the same sensory or perceptual domain. They usually are, though, and in the case of speech perception the "things" most frequently are, at least, audible. W o n d e r i n g if the child can "tell two sounds apart," the clinician produces two sounds and checks to see what the child thinks about their similarity. We should like to suggest that this cannot answer the clinically critical question, which is whether the child detects a difference between the speech forms he is expected to acquire (that is, adult surface forms) and those already stored (that is, his internal representations). Since phonology has no communicative function aside from its capacity to differentiate words, it could be said that the child's functional problem is manifested in the way he says words, not in the way he produces sounds. Inasmuch as the child's words are stored in long-term memory, his incorrect percepts, if he has them, also must be stored there. Consequently, we seek to determine whether a sound just heard differs in some i m p o r t a n t way from the child's lexically-based storage of sounds previously heard. T h a t is to say, when a person "thinks" about a sound, and is able to "re-cognize" the image o f it, he presumably experiences not a particular previous perception (which may be cognitively impossible) but some sort of composite image based on many earlier perceptions of the same functional unit. T h e composite image would be based on the input provided by speakers of varying ages, both sexes, and a wide spectrum o f idiolects. It is a phonemic category. T h e primary clinical question is whether the sound just processed and still in sensory m e m o r y is in some sense comparable to the phonemic forms that exist in lexical long-term memory. In effect, the child is asked Does this sound fall within or without the phonemic category evohed by this picture? We suggest, then, that to be clinically effective the discrimination response should (4) be based on a comparison of an adult's surface form and the child's internal representation. To determine the child's discrimination o f the adult form, his internal representation, and the control phoneme, the task must (5) present repeated opportunities for the child to reveal his perceptual decisions. A task that has one instance of a particular item or contrast simply cannot permit any conclusions about the nature of the child's perceptual behavior nor any predictions as to whether it will change or should be treated. As mentioned previously, a child who says [b] f o r / v / may r e s p o n d correctly to the only [b]-[v] trial on a discrimination task, but "the conclusion that he discriminates/b/-/v/would be no more accurate, on logical grounds, than the parallel assumption of clairvoyance were the child to call correctly one flip of a fair coin" (Locke, 1979b). T h e assumption also is made that young children will miss some items on tests that they handle perfectly well ordinarily. Even a normal-speaking child experiences a certain amount of internal noise. He is distractable, his mind wanders, and there are lots of other places he would rather be. Several years ago, Kamil and Rudegeair (1969) pointed out an obvious f a c t - c h i l d r e n with normal speech make errors on discrimination tests. Yet we can imagine no way they could have developed normal speech without normal perception. However, there are sources of error on perception tasks that do not involve perceptual ability--Locke and Goldstein (1973) found articulation-delayed four-year-olds significantly less attentive to auditory signals than similar children with good articulation, Errors will occur, but the task must (6) prevent nonperceptual errors from masquerading as perceptual errors. O n e way o f d e f e a t i n g this possibility is to p r o v i d e m u l t i p l e trials on every production-relevant item and to do qualitative analyses rather than just count the

LOCKE: Inferenceof Speech Perception, Part I 437 errors and assign a score. T h a t way, few or none of a child's behavioral e r r o r s - - t h o s e committed for n o n p e r c e p t u a l r e a s o n s - - w o u l d ever get interpreted as perceptual errors. It naturally follows that the task must be fairly short and that it must (7) require a response easily within a y o u n g child's conceptual capacities and r e p e r t o i r e of responses. Otherwise, the lengthy pretraining required just to follow instructions will d w a r f the task itself and make interpretation difficult. More serious is the fact that the test would not be used at all with many o f the children for whom the questions most need to be answered, the very young and the seriously impaired. One further criterion seems appropriate, though clinicians may disagree as to its necessity. A b o u t 80% o f children's segmental errors involve what a p p e a r to be substitutions o f one p h o n e m e for another (Templin, 1957). Investigators (Compton, 1970; Locke, 1979a) have pointed out that children's substitution errors are almost exclusively unidirectional. While one child may say [s] f o r / f / a n d another may say [j'] for/s/, few say both at the same period in their acquisition o f phonology. If children's substitutions had a purely p e r c e p t u a l basis, the child would think the i n t r u d e d p h o n e m e was able to represent the missing one, but not the converse. He might think t h a t / r / c o u l d be made either by saying Jr] or [w] but t h a t / w / c o u l d only be represented with [w]. To be maximally useful, then, the task ought to (8) allow a determination o f the direction of misperception. T h o u g h it is not certain that this distinction is clinically crucial, we identify it here so that the various tests can be appraised with it in mind. Having described some characteristics o f a clinically useful perception task, we now will examine the conventional tests to see whether they possess these characteristics. We will describe task designs, comment on particular tests, and argue that frequently no single format will be completely adequate but instead may provide a particular kind of information helpful in answering certain questions. CONVENTIONAL

TESTS

At the outset we should u n d e r s t a n d that there is a vast difference between task structure and particular tests. For example, the AX or same/different task may have particular uses, but that is not to say that any of the existing same/different tests is clinically useful. While a test can be no stronger than its basic structure, it may be a great deal weaker for a variety o f reasons. In this section, we will describe the discrimination paradigm and examine two discrimination tests, the W e p m a n (Auditory Discrimination Test, 1973) and the T e m p l i n (1957). T h e n we will describe the picture identification p a r a d i g m and analyze three specific tests, the Goldman-Fristoe-Woodcock (Test of Auditor), Discrimination, 1970), the T e m p l i n (1957), and the Boston (Pronovost and Dumbleton, 1953). Finally, we will see how well the individual tests meet the eight assessment criteria set down earlier.

The Discrimination Paradigm

Description. T h e discrimination paradigm, or AX task, presents syllable pairs in which a single p h o n e m e is contrastive. For consonants, an example would be pin-bin; for vowels, pin-pen. T h e child is instructed to say same if the paired items are considered two examples o f the same word and different if the paired items represent two different words. This task is complicated by the use o f nonsense syllables and words that, for the child, are functionally nonsense (for example, from Wepman's Auditory

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Discrimination Test, lath-lash). A subset o f items are identical phonemically (though not phonetically) and properly should be called same. Cognitive Processing. We have talked about the problem of perceiving as opposed to r e n d e r i n g some sort o f decision about what has been perceived. This matter is relevant to discrimination tasks. Consider the case in w h i c h p i n - b i n are presented and the child says same. He could have (a) perceived both stimuli correctly but not understood what the examiner meant by same and different or (b) perceived both stimuli correctly but not understood that the differentiating feature was important to the examiner; as it was not to the child, he did not r e p o r t it. One or both o f these alternatives received some s u p p o r t in a study by Beving and Eblen (1973), in which children were more accurate in their paired-syllable repetitions than in their paired-syllable judgments. In other words, by correctly repeating the items, they demonstrated knowledge o f sameness-difference and also a level o f discrimination p e r f o r m a n c e that was not manifested in the actual i~esponses o f same and different. W h e n we refer to a conceptual problem, we do not suggest that young children have no concept of sameness and difference. T h e tone and speech discrimination of day- and month-old infants makes a bit vacuous the question o f whether three- or four year olds have the concept o f same-different. T h e m o r e relevant query is whether they can handle or express it in the examiner's terms, the difference between sheer possession and active application lying in the e x p e r i m e n t a l context (Glucksberg, Hay, and Danks, 1976) or in the level of consciousness at which the concept explicitly is available. T h e child may not easily r e n d e r same and different decisions in the way the e x a m i n e r wants, and even if he does, the child may not necessarily mean by same that the paired items are not different, but that he does not regard the (detectable) difference as significant e n o u g h to say different. 1 If a child consistently is correct in his responses to AX pairs, he detects a difference between the syllables and regards it as important effough to report. I f the child fails to r e p o r t a difference between pair members, the question remains as to whether he is aware of the inter-syllabic differences not r e p o r t e d to the examiner. T h e r e also may be some variation in levels o f perceptual analysis within the AX paradigm. This variation derives from the fate of auditory information on entering the listener's cognitive system. As an auditory input, speech first passes t h r o u g h a store that records auditory detail well but for a short time (Crowder and Morton, 1969; Crowder, 1970, 1973). I f the two syllables in an AX format a p p e a r with no more than 250 msec intervals (Pisoni, 1973), the first will probably still be in this store when the second appears. This could help the child who customarily assigns two different phonemes to the same phonemic category (Locke, 1976, 1979a, in press). If, however, the interval were somewhat longer than a quarter-second, the child might already have miscategorized the first syllable when the second arrives, conceivably penalizing his decision about segments sharing a single phonemic class. (This interval is an extrapolation from laboratory work with normal-speaking adults; the relevant tests have not yet been p e r f o r m e d on phonologically disordered children.) In AX testing, d e t e r m i n i n g whether the child regards one sound as subordinate to 1In English-speaking cultures, sameness may be cognitively unmarked, with different representing the denial or negation of sameness. Probably, the subject decides if the sounds heard are sufficiently non-same to say different, not if the paired items are sufficiently un-different to say same. This scenario is supported by reaction-time studies that usually show faster responses for same than for different. (Chananie and Tikofsky, 1969; Weiner, and Falk, 1972; Pisoni and Tash, 1974).


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the other is not possible; we cannot answer the directionality question raised earlier. It is only possible to determine whether the child acts as if the two sounds were different. More importantly, the AX task looks only at surface-to-surface discrimination, ignoring altogether the question o f whether the child is able to discriminate an adult surface form from his own internal representation. Discrimination Tests. Two discrimination tests are used commonly, the W e p m a n test (Auditory Discrimination Test, 1973, reviewed in detail in Locke, 1979b) and the T e m p l i n test (Templin, 1957). Both contain syllable pairs, the W e p m a n test pairing words, the T e m p l i n using nonsense syllables. T h e basis for the pairings should be child speech, contrasting phonemes that children often confuse in production. These two tests do not do that. In addition, they contain many contrasts children never confuse in speaking. For example, we know from Snow's data (Snow, 1963) on speech production errors in 438 first graders, that 86/438 said [b] for /v/ wordinitially; 0/438 said If] f o r / v / o r [v] f o r / f / w o r d - i n i t i a l l y . Yet it is the latter item that appears on the W e p m a n test while t h e / b / - / v / c o n t r a s t is not tested. T h e W e p m a n test contains the item moon-noon, but all 438 o f Snow's subjects said initial /m/ a n d / n / correctly. I f the test is to be used in the assessment o f production-relevant perception, why would anyone wish to test that contrast? If the child errs on it, we are immediately in a theoretical q u a n d a r y because the child articulates correctly sounds he gives no evidence o f perceiving correctly. This information can contribute to a r e d u c e d score, yet it is h a r d to see what use it could have clinically. Table 1 shows the 12 most c o m m o n phonemic confusions in three word positions observed by Snow (1963) in her extensive study o f first grade children's speech. 2 T h e confusions are bidirectional; hence the/f/-/0/confusion in the initial position o f words reflects the n u m b e r o f [f]s f o r / 0 / ( 1 4 5 ) plus the n u m b e r of [0]s f o r / f / ( 1 ) , for a total o f 146. Since all 438 children had two opportunities to reveal a phonemic confusion (two words/phoneme), the p r o p o r t i o n of confusions for ~U-~O~ is 146/876 or 0.167. T h e W e p m a n and T e m p l i n Tests o f Discrimination a p p e a r on the left o f Table 1. T h e W e p m a n test contains only six of the 36 most c o m m o n errors, the Templin, zero. This means that 34 o f the W e p m a n items and all 50 o f Templin's items are irrelevant to these most c o m m o n phonemic confusions in children. In practice, if a child missed every phonetic contrast he did not preserve in his speech, but only those, he would still get 83% correct on the W e p m a n and 100% correct on the Templin. T h a t the items in these tests are of little clinical relevance in general is a serious problem. However, even if the items were chosen with careful recourse to child phonology data, they. still would not be relevant to the speech problems of any particular child. Assume t h a t / f / - / 0 / i s included as an item on the test, correctly observing that this is m o r e o f a production problem than/t/-/0/. T h a t may help the majority o f children, but it will not help the child who does say [t] for/0/. These problems are due to the fact that the items were chosen before the child was met, much less given a speech test that would provide a phonological inventory from which items could be selected. A n attendant problem arises when one comes to a phonetic context that really is production-relevant (for example,/t/-/0/)--the child gets only one chance at it. Since the probability o f his getting it right by chance is 0.50 (the task being binary), it is h a r d to see how one could draw any conclusions from his response even though 2Certain dialectal (for example, d3/3, which came mostly from garage and mirage), morphological (for example, n/o, which came mostly from swimming), and allophonic (for example, w/hw) "errors" have been omitted.

440


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TABLE 1. T h e 36 phonemic oppositions most commonly collapsed in the speech of 438 first graders and the probability of each collapse (extrapolated from Snow, 1963, Table 1; /d3/-/3/, /n/-/rj/and/hw/-/w/were excluded as dialectal, morphological, and allophonic variations, respectively). A (+) indicates that the opposed phonemes (#'s designate omissions) are compared directly at least once, a ( - ) that they never are compared on a particular test. The % oppositions excluded by a test is shown at the bottom of the table. These percentages also constitute the score obtained, theoretically, by any child who consistently misperceives every phonemic contrast he fails to effect in speech production. I

Discrimination Wepman Templin

G-F-W

Picture Identification Templin Boston

Word-initial 1. 2, 3. 4. 5.

/f-0/ /b-v/ /~5-#/ /w-r/ /s-J/

0.167 0.164 0.098 0.088 0.069 6. itS-f~ 0.063 7. /s-z/ 0,054 8. /O-s/ 0.038 9. /w-l/ 0.027 10. /d-~5/ 0.027 11. /d-g/ 0.020 12. /l-j/ 0.020

_

_

+

-

+

--

+

-

-

_

_

_

+

+

_

- -

÷

- -

- -

÷

.

.

.

+

.

Word-medial 1. /t-0/

0.160

2. ~f-O~ 0,158 3. ~s-f~ 0.115 4. 5. 6. 7. 8. 9. 10. 11, 12.

/dqS/ /s-0/ /0-#/ /b-v/ /z-3/ /n-I3/ /s-z/ /w-r/ /d-g/

0.083 0.075 0.064 0,054 0.053 0.045 0.038 0.026 0.024

u

m

m

M

n

n

w

m

Word-final 1. 2, 3. 4. 5. 6, 7. 8. 9. 10. 11. 12.

/v-~5/ 0.243 /r-#/ 0.205 /1-#/ 0.185 /f-0/ 0.152 /s-S/ 0.115 /s-z/ 0,092 /f-v/ 0.075 /0-~/ 0.061 /z-3/ 0.051 /d-b/ 0.042 /tJ'-d3/0.040 /b-v/ 0.040

+

m

m

m

m

m

÷ +

i

m

m

+

m

m

m

m

m

m

i

0

3

3

Included items

6

Excluded items

30

36

33

35

33

% exclusion

83

100

92

97

92

1


441

it did involve a clinically-relevant contrast. T h e m a i n p r o b l e m is that on n e i t h e r test can one d e t e r m i n e w h e t h e r the child's speech p e r c e p t i o n is related to his speech p r o d u c t i o n , a n d that is the clinical q u e s t i o n o n e o r d i n a r i l y seeks to answer. Clinical Potential. T h e p o t e n t i a l b e n e f i t o f the d i s c r i m i n a t i o n f o r m a t - - n o t the specific tests--is that it could say s o m e t h i n g a b o u t what the child r e g a r d s as discriminable. H o w e v e r , the scope o f that discriminability is restricted to adult f o r m s as they are processed t h r o u g h echoic m e m o r y . W h e n one was finished with A X testing, e v e n w h e n the child r e s p o n d e d correctly o v e r a series o f trials, questions w o u l d remain as to w h e t h e r he could discriminate the t a r g e t s o u n d f r o m his i n t e r n a l r e p r e sentation a n d w h e t h e r he c o u l d h e a r a d i f f e r e n c e between his f o r m o f the target and the f o r m stored in his p h o n o l o g i c a l system. W e r e the response incorrect, one also TABLE 2. The eight criteria for a clinically useful assessment of speech perception, and the extent to which each criterion is met (+) or failed ( - ) by the individual tests.

Discrimination Wepman Templin

G-F-W

Picture Identification Templin Boston

The procedure should: 1. examine the child's perception of replaced sounds in relation to replacing sounds 2. observe the same phonemes in identical phonetic environments in production and perception 3. permit a comparison of the child's p e r f o r m a n c e on target and replacing sounds with his discrimination of target and perceptually similar sounds 4. be based on a comparison of an adult's surface form and the child's internal representation

÷

÷

÷

+

+

+

5. present repeated opportunities for the child to reveal his perceptual decisions 6. not permit nonperceptual errors to masquerade as perceptual errors 7. require a response easily within a y o u n g child's conceptual capacities and repertoire of responses 8. allow a determination of the direction o f misperception

442 JOURNALOF SPEECH AND HEARING DISORDERS

XLV 431-444

November 1980

would be left wondering whether the child could process the sounds correctly when p e r f o r m i n g a task less sensiti,,e to hk internal criterion o f sameness and difference. Table 2 shows the two AX tests viewed against the eight criteria described earlier. As the Table indicates, all eight are failed by the specific AX tests. Consequently, we can see little reason to use these tests in the assessment of phonological disorders in children. The Picture I d e n t i f i c a t i o n P a r a d i g m

Description. In assessing p h o n e m e perception by way o f picture identification tasks, the child is shown two, three, or four pictures with labels or descriptive terms that differ in a minimal way phonemically (for example, man-fan-pan-can). T h e examiner says or plays a taped form of one o f the words; the child is to point to the correct picture. Cognitive Processing. Unlike the discrimination format, the identification paradigm never asks the listener if a p a r t i c u l a r p h o n e m e is d i f f e r e n t f r o m some o t h e r phoneme. This is a j u d g m e n t that the examiner makes on the basis o f an accumulation of differential identifications of the two phonemes. How a child decides which picture represents what the examiner said is not clear. If we assume that the child unequivocally accepts each picture label the examiner uses, the child may conceivably make an exhaustive search of the full array before making a decision, j u d g i n g each picture label independently. It seems more likely that, having heard the label, the child begins a search for something that could be represented by that word. I f this is the case, it may also be true that each picture label does not contribute equally to the data. For the set vine-sign-line-shine, if the child hears vine and points to vine, does this mean he discrirninated /v/ from /s/, /1/, a n d / f / ? Has he, o n ' t h e other hand, conducted a self-terminating search, finding vine on the display without fully taking in each of the four pictures and d e t e r m i n i n g the phonetic composition of their names? Without knowing the answer to these questions, it is impossible to know from which sounds the target was discriminated. In any event, the child apparently cannot respond correctly unless he perceives the word more or less accurately and remembers it long enough for it to survive a search process in which he scans the individual pictures, consulting his long-term phonological memory for phonemic name matches. If the phonetic form in sensory or shortterm memory is close e n o u g h to the phonemic form in long-term memory, that picture is the right choice. We said "more or less" because if the child thinks he heard bine, his best bet still would be vine b e c a u s e / b / i s closer t o / v / p e r c e p t u a l l y than to/s/, /1/, and/J'/. Unlike discrimination tests, picture identification procedures require little pretraining. I f several pictures are placed in front of a young child and the name of one o f them is said, he probably will point to it. Unlike the conventional discrimination test format, it is possible with picture identification tests to determine the directionality o f perceptual confusion because the child points to the picture with a name perceptually closest to the one he believes was uttered. While the instructions ale easy to follow, training is n e e d e d in the particular labels used. Often, the labels the examiner has in mind are different from the names a child will use in representing the pictures. These problems can be dealt with to a limited extent. T h e major problem with picture tests, one which renders them practically useless for most clinical purposes, is that most production-relevant contrasts cannot easily be represented with pictures.


443

Picture Identification Tests. We will consider three p o p u l a r picture tests, the T e m p l i n (1957), the G o l d m a n - F r i s t o e - W o o d c o c k (1970) a n d the Boston (Pronovost a n d Dumbleton, 1953). In T e m p l i n ' s test there are 59 picture pairs. We again used Snow's (1963) data to d e t e r m i n e the likelihood that a first g r a d e r would confuse any pair o f sounds contrasted in Templin's test, that is, name the two pictures homonymously. T h e probability o f that occurring for Templin's contrasts (excluding the six vowel contrasts and 14 not tested by Snow) is two in a thousand. In short, the test does not examine sounds commonly confused in production (Table 1 shows that only one o f the 59 items is relevant to the 36 most c o m m o n production confusions) and does examine many that are never confused in production (for example, /d/-/f/, /n/-/g/, /s/-/p/). On the G o l d m a n - F r i s t o e - W o o d c o c k Test of Auditory Discrimination (1970), only three o f the 36 most commonly confused contrasts are tested, even though the test uses four pictures per trial instead o f two. A significant criticism derives from a rather subtle statistic--Goldman, et al show, with their test (in their Table 2), that discrimination improves from 3.5 to 34 years. Yet articulation reaches asymptote by eight years (Templin, 1957). T h e GoldmanFristoe-Woodcock test obviously is testing a behavior largely irrelevant to speech production because it keeps getting better long after speech has stopped improving, T h e r e is one other p o p u l a r picture test, the Boston test (Pronovost and Durableton, 1953). Unlike the other tests, the Boston uses three picture pairs (for example, cat-cat/cat-bat/bat-bat), one o f which is n a m e d by the examiner. Table 1 shows that the Boston test examines three of the 36 most commonly confused contrasts. Clinical Potential. T h e r e is, in the picture identification format, something o f potential value--it may be free of the criterion or j u d g m e n t problems that occur in discrimination testing. However, pictures that represent children's production-relevant contrasts largely are unavailable, and for most children there will be too few items that capture their phonological confusions. As Table 2 indicates, the picture identification tests reviewed meet two o f the eight criteria listed earlier: they permit a comparison of an adult's surface form with the child's internal representation and they require the developmentally early pointing response (though this is less clearly "early" in the Boston test). T h e G o l d m a n Fristoe-Woodcock test allows a directionality determination, though there are too few trials for this to be reliable. However, none of the AX and identification tests employ production-relevant contrasts or production-relevant control items and none permit r e p e a t e d opportunities to observe relevant contrasts when they do appear. T h e r e are a few other commercially available tests, but due to space limitations readers are encouraged to appraise these tests for themselves. However, since no tests now sold (a) are a series o f blanks into which the child's production confusions may be e n t e r e d or (b) contain perceptually similar control items, relying on these other tests is inadvisable. ACKNOWLEDGMENT

This work was supported, in part, by NICHD Grant HD-05951 and NIMH Grant MH 31965-01. Requests for reprints should be addressed to the author at the Department of Hearing and Speech Sciences, University of Maryland, College Park, Maryland 90742. REFERENCES

BERNTHAL,J. E., and WEINER,F. F., A re-examination of the sound omission--preliminary considerations.J. Child Commun. Dis., 1, 132-138 (1976).

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