Top Lang Disorders Vol. 31, No. 2, pp. 96–111 Copyright c 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Differentiating Delay From Disorder Does it Matter?

Barbara Dodd

Aim: The cognitive-linguistic abilities of 2 subgroups of children with speech impairment were compared to better understand underlying deficits that might influence effective intervention. Methods: Two groups of 23 children, aged 3;3 to 5;6, performed executive function tasks assessing cognitive flexibility and nonverbal rule abstraction. Following the system of differential diagnosis of speech disorders first described by Dodd, Leahy, and Hambly (1989), one group was identified as having delayed speech development, as their non–age-appropriate speech error patterns were typical of younger children. The other group was diagnosed as disordered because children consistently used at least one speech error pattern atypical of any age group in an assessments’ normative sample (Dodd, Zhu, Crosbie, Holm, & Ozanne, 2002). Results and Conclusions: The disordered group performed less well than the delayed group: They had poorer cognitive flexibility and difficulty abstracting nonlinguistic rules. They made more consonant errors and different types of errors. The 2 groups did not differ on measures of , vowel accuracy, or consistency of multiple productions of the same words. The findings suggest that different interventions, reflecting knowledge of underlying deficits, might benefit specific subgroups of children with speech impairment. Key words: cognitive flexibility, error patterns, executive functions, speech delay, speech disorder

LL YOUNG CHILDREN make errors 5 years. Researchers have argued that error A when pronouncing words (e.g., [pun] pattern change indicates linguistic reorgani- spoon; [tæt] cat). Most children of a partic- zation of the phonological system that occurs ular age share the same error patterns, with in a systematic order, within specific time different error patterns characterizing spe- frames and without explicit instruction (Grun- cific age bands. In English, for example, stop well, 1977; Macken, 1979; Williams, 1993). may initially be pronounced as [tɒ], followed Reorganization reflects cognitive-linguistic de- by [tɒp], then correctly as [stɒp]. English- velopment that allows children to identify speaking children’s speech comes to resem- the phones, contrasts, and phonotactic con- ble the adult-target production by around straints of the language being learned. Although most children exposed to the same language use error patterns that resolve Author Affiliation: Department of Language and at somewhat similar ages (Grunwell, 1997; Communication Sciences, City University, London, United Kingdom. Preisser, Hodson, & Paden, 1988), this is not The study reported was funded by the Australian Re- the case for all children. The most common search Council Discovery Grants Scheme. diagnosis made by clinicians working with The willing cooperation of childcare centers, parents, pediatric caseloads is speech impairment.1 and children is gratefully acknowledged. The author Children’s errors make their speech difficult thanks Beth McIntosh, Sharon Crosbie, Aileen Wright, and Alison Holm for practical help and discussion. Corresponding Author: Barbara Dodd, PhD, De- partment of Language and Communication Sciences, City University London, Northampton Square, London 1The term “speech impairment” is used rather than the EC1V OHB, United Kingdom (e-mail: Barbara.Dodd.1@ current generic term “,” which city.ac.uk). denotes all speech difficulties including both delay and DOI: 10.1097/TLD.0b013e318217b66a disorder. 96 Differentiating Speech Delay From Disorder 97 to understand resulting in communication role of cognitive-linguistic abilities for typi- breakdowns that place them at risk for so- cal phonological development followed by a cial and academic, particularly literacy, fail- summary of findings from research compar- ure (Gillon, 2004). The National Institute on ing children with delayed as opposed to dis- Deafness and Other Communication Disor- ordered speech impairment. Delayed speech ders (1994) estimated that 10% of children development is defined by the presence of receive intervention for impaired speech in- speech error patterns, each observed in at telligibility in the United States. An incidence least five different lexical items in a 50-word survey of a speech-language pathology service picture-naming task, that are typical of at least in England (Broomfield & Dodd, 2004a), re- 10% of children of a younger chronological ported that 6.4% of all children are treated for age in the normative data for that standard- speech impairment. ized assessment. To be classified as having Successful intervention for speech impair- disordered speech, children must evidence at ment relies on clinicians’ knowledge of least one speech error pattern, identified as the nature of the deficit underlying chil- occurring at least five times in different lexi- dren’s impairment (Stackhouse & Wells, cal items in the 50-word task, that is atypical of 1997). Although some children with speech any age group in the normative sample for the impairment have been shown to have assessment. deficits in input (e.g., Boets, Ghesquiere, van Wieringen, & Wouters, 2007) or output (e.g., motor processing, Gibbon, 1999), many re- Typical speech development searchers have argued that most children’s Three primary factors are posited as alter- speech impairment reflects a linguistic (i.e., native explanations for developmental errors phonological) impairment (Bowen, 2010; in speech during the acquisition of phonol- Gierut, 1998; Stackhouse & Wells, 1997; Vih- ogy: output, input, and cognitive linguistic man, 1996). This hypothesis was examined by processing. a study comparing the auditory-visual speech 1. Output approaches: Motor theory holds perception, oral-motor ability, and cognitive- that children gradually master the intri- linguistic processing skills of 78 children with cacies of sequencing complex articula- speech impairment (mixed delay and disor- tory movement that reflects more gen- der) and 87 age-matched controls aged 3 to 6 eral motor maturity (e.g., Green, Moore, years (Dodd & McIntosh, 2008). No child in & Reilly, 2002). For example, McCune the group with speech impairment was identi- and Vihman (2001) argued that children fied as having an input difficulty, and only two establish “vocal motor schemes” for con- children performed below the normal range sonant production that influence the er- on an oral sequenced-movements task. In con- ror types made in early phonological de- trast, the group with speech impairment per- velopment. formed significantly less well than controls on 2. Input approaches: Immature input pro- both cognitive-linguistic tasks of rule abstrac- cessing has been claimed to explain de- tion and cognitive flexibility. velopmental errors. Some researchers ar- This article examines the processes2 of cog- gue that, as children’s ability to discrim- nitive flexibility and rule abstraction in chil- inate differences between the speech dren with speech impairment. The literature sounds of their native language gradually review first highlights the importance of the improves, it allows more accurate pro- duction (e.g., Edwards, Fox, & Rogers, 2002). Discrimination tasks might, however, evaluate phonological learn- 2The term “processes” refers in this article to the cogni- ing rather than auditory-visual speech tive abilities underlying phonological development. perception. For example, Burnham, 98 TOPICS IN LANGUAGE DISORDERS/APRIL–JUNE 2011

Earnshaw, and Clark (1991) showed that Speech impairment the development of the ability to discrim- Children with speech difficulties are het- inatespeechsoundsis“tuned”postin- erogeneous, differing in severity, underlying fancy. The infant ability to discriminate cause, speech error characteristics, profile of contrasts not relevant to their native lan- associated abilities and response to treatment. guage (Jusczyk, 1992) is lost so that chil- In Broomfield and Dodd’s (2004b) incidence dren older than 2 years are unable to study, 320 children with speech difficulties discriminate between similar sounds that were assessed. Of this group, 12.5% had an ar- are not native language phonemes. ticulation disorder, which was defined as an 3. Cognitive-linguistic processing appro- inability to produce a perceptually acceptable aches: Cognitive-linguistic approaches version of phones due either to a physiolog- propose that children’s ability to process ical condition such as dysarthria or mislearn- speech changes over time, reflecting the ing of the sounds’ motor program (e.g., lisp). development of other general mental Most of the children assessed (57.5%) had a abilities such as phonological working phonological delay characterized by all errors memory (Adams & Gathercole, 2000), being accounted for by phonological error processes for forming and revising lexi- patterns (e.g., cluster reduction and fronting) cal representations (Elbro, 1993), and/or that occur during typical speech development cognitive capacities for rule abstraction at a younger chronological age level. Chil- (Dodd & Gillon, 1997). dren who used one or more error patterns We studied the contribution of input, that were atypical of normal development output, and cognitive-linguistic abilities to in English (e.g., backing, favored sound, and phonological development in one group of 2- initial consonant deletion) were classified as year-old children (Dodd & McIntosh, 2010). having consistent atypical phonological disor- We measured the perception of conflict- der. This group, constituting 20.6% of the 320 ing heard and lip-read speech, production children referred, made a significantly greater of isolated and sequenced oral-motor move- number of errors than the children with artic- ments, and verbal and nonverbal rule abstrac- ulation difficulties and delayed phonology. An tion abilities of 62 children aged between additional 9.4% of children pronounced the 25 and 35 months. All three domains were same lexical item using different error forms shown to contribute to phonological accu- on at least 10 of the 25 words that were as- racy, although regression analyses showed sessed three times within one assessment ses- that the contribution of rule abstraction abil- sion (see Dodd, Holm, Crosbie, & McIntosh, ity to phonological accuracy exceeded that of 2010). both input and output factors. The findings The focus of this article is on two of the sub- were interpreted as evidence for cognitive- groups of children with speech impairment linguistic ability being the primary determi- described by Broomfield and Dodd (2004b): nant of 2-year-olds’ phonological develop- delay and disorder. The reasons for choosing ment. It seems likely, then, that children who these two groups are that they are the two are classified as speech disordered because largest subgroups (57% and 21%), and they they abstract nondevelopmental phonologi- are similar in that they have no oral-motor cal constraints would perform more poorly difficulties, but their speech is characterized on measures of rule derivation than children by the consistent use of non–age-appropriate whose phonology is merely delayed. Conse- phonological error patterns. Previous re- quently, the current article focuses on the dif- search on these two groups can be com- ference between the cognitive-linguistic abil- pared on four parameters: associated abili- ities of children with delay as opposed to dis- ties, literacy, natural history, and response to order. intervention. Differentiating Speech Delay From Disorder 99

Associated abilities & Hambly 1989; Harris, Botting, Myers, & Auditory-visual speech perception is Dodd, in press). demonstrated by an illusion (McGurk & Literacy MacDonald, 1976) that occurs when listen- It is well established that children with ers perceive /ta/ although hearing /pa/ in speech impairment are, as a group, at risk synchrony with the lip movements for /ka/. for literacy difficulties, as has been shown Dodd, McIntosh, Erdener, and Burnham by studies comparing children with impaired (2008) compared 22 children with delayed speech and typically developing controls speech development with 12 children whose (e.g., Snowling, Adams, Bishop, & Stothard, speech was disordered, on a same–different 2001). Other studies have examined the liter- judgment task assessing perception of the acy abilities of children with impaired speech illusion. Neither group perceived many in greater depth in an attempt to under- illusions. Children with disorder, however, stand why a significant number of children usually reported the auditory component with impaired speech learn to read and spell of the illusion, whereas the responses of without difficulty (Leitao & Fletcher, 2004). those with delay were more evenly split Surface speech errors may allow identifica- between the auditory and visual components tion of deficits underlying differences in lit- of the illusion. These findings indicated that eracy development. One recent study (Harris children with disordered speech differed et al., in press) investigated the rela- in their phonological processing of the tionship between type of speech impair- auditory-visual speech illusion from children ment, phonological awareness and liter- with phonological delay. One plausible acy in children aged 5;2 to 7;9. The hypothesis is that the children with disor- children had either delayed phonology dered phonology had difficulty learning the (n = 8), disordered phonology (n = 5), or consistent relationships between heard and were typically developing controls (n = 6). seen speech. They were compared on tasks measuring syl- Phonological awareness refers to the abil- lable and onset-rime awareness, letter knowl- ity of children to implicitly acquire knowl- edge, phonological rule knowledge, and real- edge of the phonological constraints (i.e., word and nonword reading. Children with how speech sounds can be combined to delayed speech development performed like make words) of the language they are typically developing controls on all phono- learning (Stackhouse & Wells, 1997). Sound logical awareness and reading measures. Chil- sequences that do not conform to those con- dren with speech disorder, who consistently straints are termed “illegal.” Phonological le- made errors atypical of normal development, gality tasks are often used to assess chil- had difficulties on all phonological awareness dren’s knowledge of the phonological system tasks with the exception of syllable aware- (Stackhouse & Wells, 1997). Children might ness. None of the children with disorder could be asked, for example, to choose between read and they showed no measurable emer- two nonsense names that differ by one gent reading ability such as letter recognition. phoneme, making one word phonologically Findings from this small-scale study re- legal and the other illegal (e.g., [frim] and flect previous research. For example, Leitao [srim] as a name for a monster). Research has and Fletcher (2004) reported that children indicated that children with phonological de- with speech impairment who made errors lay perform like typically developing peers, atypical of normal speech development have showing a significant preference for phono- the most difficulty acquiring literacy. Leitao, logically legal words, whereas children with Hogben, and Fletcher (1997) had previ- disorder (who make consistent errors) per- ously found that a mixed group of chil- form at chance level on this task (Dodd, Leahy, dren with speech disorder and delay differed 100 TOPICS IN LANGUAGE DISORDERS/APRIL–JUNE 2011 significantly from a control group on all errors and a child who had previously made measured aspects of phonological awareness, age appropriate errors was diagnosed with de- supporting the notion that speech difficulty lay. Another study of children on a 6-month is associated with impaired development of waiting list for speech therapy in the United phonological awareness skills. Further analy- Kingdom showed that children with speech sis, however, showed a bimodal distribution. disorder did not make progress without in- A proportion of children with speech impair- tervention, whereas children with delay did ment achieved scores similar to those of the (Broomfield & Dodd, 2005). controls, whereas the remainder showed sig- nificant difficulty with all tasks. No correlation Response to intervention was found between severity of speech im- Stackhouse and Wells (1997) argued pairment and phonological awareness. Nine that only treatment targeting the speech- of the eleven subjects who had consistent processing deficit underlying a child’s speech phonological disorder were found to have se- disorder will result in efficient systemwide vere phonological awareness difficulties com- change. One clinical trial (Alcorn, Jarrett, pared with one in seven of the phonologi- Martin, & Dodd, 1995) reported the outcome cally delayed group who performed like con- of a 2-week intensive whole language therapy trols. These findings might explain conflicting for 12 children who had delayed or disordered reports in the literature about the relation- error patterns. There was a significant im- ship between speech impairment, phonolog- provement in receptive vocabulary, number ical awareness, and literacy. of words pronounced accurately in sponta- neous speech, and phone repertoire between Natural history pre- and postprogram and maintenance mea- Risk factors for speech impairment have re- sures. There was no change, however, in the ceived increased attention in the search for number of atypical error patterns used, or genetic markers (Shriberg et al., 2005). One the number of atypical errors made, suggest- study of 100 German-speaking children with ing that although whole language intervention speech impairment (Fox, Dodd, & Howard, led to positive change for delay, disordered 2003) indicated that children with delay were speech showed limited change. Both delayed more likely to have a reported history of and disordered phonology, however, can be more than four episodes of middle-ear infec- successfully addressed by phonological con- tion with effusion than controls or other chil- trast intervention (Dodd et al., 2008). dren with speech impairment. The only risk factor for children with consistent disorder Research hypotheses was reported history of speech disorder in the The research reviewed indicates that dif- family. ferent deficits may underlie delayed and Measurement of spontaneous progress disordered subgroups of speech impairment. without treatment is rarely possible because Differences are reported for the two groups’ of ethical concerns. One small study assessed profiles of associated abilities, literacy, natural Putonghua-speaking children in a Beijing nurs- history of acquisition, and response to ther- ery, where no speech-language pathologist apy (although this factor provides the weak- services were available. The first assessment est evidence). Two symptoms mark the dif- identified two children who made consis- ference between the two groups: the type of tent atypical errors and three children with speech error patterns used and the number phonological delay according to developmen- of speech errors made. Children with disor- tal norms (Zhu, 2002). At a second assess- der use some error patterns that do not oc- ment, 9 months later, the disordered children cur during typical phonological development. remained disordered, whereas one of the chil- This may reflect an impaired ability to ab- dren with delay now made age appropriate stract the rule-based system of constraints that Differentiating Speech Delay From Disorder 101 governs each language’s phonological system. in fewer than 10% of the population (e.g., It is hypothesized that children with consis- backing of alveolar stops, initial conso- tent speech disorder will perform less well nant deletion). than children with delayed phonological de- The children with delay were matched pair- velopment on measures of rule abstraction wise, as far as possible, for age and gender and cognitive flexibility. with children diagnosed as having phonolog- ical disorder. The diagnostic criteria for dis- METHODS ordered rather than delayed speech develop- ment were as follows: Participants 1. Performance more than 1 SD below the The data presented in this article come from mean on the DEAP (Dodd et al., 2002) 46 children drawn from a large-scale study on measures of PCC; that examined preschool children’s speech 2. Children consistently used at least one development. In the larger study, the in- speech error pattern, identified as occur- put processing, executive function and oral- ring at least five times in different lexical motor abilities of 275 children were assessed items, that was atypical of any age group (see Dodd & McIntosh, 2008). All children in the normative sample for the DEAP were referred to the large study by their par- (Dodd et al., 2002). In addition, many of ents following advertisements in preschools, these children evidenced error patterns childcare centers, and parish newsletters in typical of children of a younger chrono- Brisbane, offering free assessment of speech logical age. and language abilities by qualified speech- All children had language abilities within language pathologists. In this article, data are normal limits as determined by standardized reported for a subset of children from that assessment (The Quick Test of Language, large study. The children included were all McIntosh & Liddy, 2006; see materials sec- children identified as having delayed speech tion). Apart from language disorder, other development (n = 23) and children with dis- exclusion criteria were bilingualism, current ordered speech development (n = 23) who hearing impairment, and neurological or cog- were selected from the data base to be closely nitive impairment. There were more boys matched for age and gender. than girls in the sample: 11 girls and 35 The 23 children who were diagnosed with boys. The mean age of the children with delayed speech development met the follow- speech delay was 4;7 (SD: 8 months; range ing criteria: 41–66 months). For the disordered group the 1. Performance more than 1 SD below the mean age was 4;4 (SD: 7 months; range 39– mean on a standardized speech assess- 65). A one-way analysis of variance (ANOVA) ment (The Diagnostic Evaluation of Ar- showed that there was no significant differ- ticulation and Phonology—DEAP; Dodd, ence in chronological age between the de- Zhu, Crosbie, Holm, & Ozanne, 2002) on layed and disordered groups; F(1, 44) = 2.556, measures of percent consonants correct p = .117. (PCC); Case history information was gained by ask- 2. All speech error patterns identified as oc- ing parents to complete a questionnaire when curring at least five times in different lex- they signed consent forms. Socioeconomic ical items were typical of a child of a status was determined by completed years of younger chronological age; mothers’ education (Hoff & Tian, 2005). For 3. When naming the 50 words of the the mothers of children with speech delay, DEAP’s phonology subtest, no child 29% had completed 11 years and 62% had made more than four atypical errors, on completed tertiary education (16 years), in the basis of normative data where an comparison to 17% and 52% for mothers of the atypical error pattern was one identified children with disordered speech. The number 102 TOPICS IN LANGUAGE DISORDERS/APRIL–JUNE 2011 of children who had a history of treatment for population of Queensland children. This test ear infections was 30% for the delayed group is based on Blank, Rose, and Berlin’s (1978) and 52% for disordered group. The propor- concept of four language levels. Level 1 in- tion of children with a reported family history cludes reporting and responding to salient in- of speech or language difficulties was 40% for formation, for example, “What is this called?” the delayed group and 48% for the disordered (pointing to a picture of a toothbrush). Level group. Of the children with delay, 39% were 2 involves reporting and responding to de- first born in the sibling order compared with lineated and less salient clues, for example, 35% of children with disorder. Statistical anal- “What do we do with it?” (pointing to a pic- yses are not reported for these data because ture of a toothbrush). Level 3 assesses the use of small numbers, which may account for the of language to restructure perceptual input slightly lower than expected reports of fam- and inhibit predisposing responses, for exam- ily history of communication difficulty for the ple, “At the farm, a boy saw something that disordered subgroup. However, apart from was not an animal. What could he have seen?” unexpectedly low levels of reported otitis me- The most difficult level involves the use of dia with effusion for the delayed children, the language to predict, reflect on, and integrate groups seem reasonably well matched. ideas and relationships, for example, “Why can’t the girl reach the cat?” (pointing to a Procedure picture of a cat on a roof and a girl crying). The children were assessed in their home, The test has a total of 30 randomized stimulus at their preschool, or in their child-care cen- questions, where 21 questions have a picto- ter in a relatively quiet space, in two 30- rial stimulus. Children start and finish with a min sessions, usually on the same day. In Level 1 question to give a feeling of success. one session, their speech ability was assessed The test takes 10 min to administer and has using all subtests of the DEAP (Dodd, Zhu, been shown to have good reliability and valid- Crosbie, Holm, & Ozanne, 2002), as well as as- ity (McIntosh & Liddy, 2006). sessment on the Flexible Item Selection Test (FIST; Jacques & Zelazo, 2001) and a language Diagnostic Evaluation of Articulation screening measure (Quick Test of Language; and Phonology McIntosh & Liddy, 2006). In the other ses- The standardized speech assessment used sion, they were asked to perform the input consists of five subtests that enable the tester processing task and a rule abstraction execu- to differentiate between disorders of articula- tive function task. The order of presentation tion (organic and functional), delayed phono- of the tasks was randomized within sessions. logical development, consistent and incon- Data on the groups’ performance on the in- sistent phonological disorder, and childhood put tasks are reported elsewhere (see Dodd apraxia of speech. All children first com- et al., 2008) and discussed in the introduc- pleted the Diagnostic Screen and the Oro- tion to this article. Few children performed Motor Test (diadochokinetic test, isolated and below the normal range on oral-motor tasks sequenced oromotor movement). In the orig- and those data were presented in Dodd and inal large scale study, those children perform- McIntosh (2008). This article presents data ing within normal limits on the Diagnostic from the speech assessment and executive Screen were allocated to a typically devel- function tasks. oping control group (see Dodd & McIntosh, Materials 2008); their data are not reported in this study. Those who failed the Diagnostic Screen The Quick Test of Language were given the Phonology Assessment, allow- The children’s language skills were assessed ing calculation of PCC, single words versus using the Quick Test of Language (McIntosh & connected speech agreement, and descrip- Liddy, 2006), a screening test standardized on tion of error patterns. Children identified as Differentiating Speech Delay From Disorder 103 producing speech characterized by multiple times as a relevant nonmatching cue (e.g., error forms for the same lexical items on “small” in the large red teapot,asmall red the Diagnostic Screen, were also administered teapot,andalarge red shoe trial) and twice the Inconsistency Assessment. Children who as an irrelevant cue (the cue that remains con- scored above the criterion of 40% inconsis- stant across all three items). All children ini- tency were excluded from the analyses pre- tially completed ten orientation trials (three sented in this article. Item Identification trials, four Favorite Items trials, and three practice trials) followed by Flexible Item Selection Test (FIST) the 15 experimental trials of the FIST. The Flexible Item Selection Test (FIST; Jacques Item Identification Task was administered to & Zelazo, 2005) was designed as a measure of ensure children could identify all of the di- executive function. Children are shown three mensions and cues in the FIST. The Favorite pictures (e.g., a large red boat,alarge yel- Items Task oriented children to the task (i.e., low boat,andalarge yellow shoe)on21× the need to point to pictures). Jacques and 29.7 cm white cards (printed version of the Zelazo’s (2005) presentation order 1 was used computerized FIST; Jacques & Zelazo, 2005). in this experiment, where the placement of Children were asked to “Show me two pic- items that matched on a dimension was coun- tures that go together” (Selection 1). In this terbalanced. trial, children needed to match two pictures by pointing to ones that were the same shape The nonlinguistic rule abstraction task (e.g., both boats), or by color (e.g., both yel- The nonlinguistic rule abstraction task low); size was not a relevant cue in this trial. (Dodd & McIntosh, 2008) required children Children were then given an acknowledge- to sit facing a 34 ×26.5 cm computer touch ment irrespective of response accuracy and screen that presented the stimuli. There were the next instruction “Well done. Now show four practice trials to teach the task. Children me two other pictures that go together” (Se- first saw a 15 × 15 cm yellow square that they lection 2). Children had to reselect one of the were told to touch. When touched, the square pictures indicated in Selection 1 and match disappeared to reveal a 3-s animation (cocka- it with another picture on a different con- too flapping its wings, a puppy sitting up in ceptual dimension. For example when shown a box, or a seal spinning a ball on its nose). acardwithalarge red teapot,asmall red The next stimulus was a red 15-cm equilat- teapot,andalarge red shoe, children might eral triangle. When they touched it, children first select the two pictures with the same saw one of the three animations. The third shape (teapots) and when asked for another trial presented an 11-cm equilateral red trian- two pictures that went together, select the gle and a yellow circle with a diameter of 11 two large items (matching size). Color is an cm. When one of these shapes was touched, irrelevant cue in this trial because all pictures there was a “boing” electronic noise, but no are red. animation appeared. The experimenter said On each trial, then, participants were “You must have touched the wrong one. Try shown three items devised from a combi- this next one.” A red triangle and a purple nation of three dimensions: color, shape, square appeared on the screen and children and size. There were three cues within were told to touch the one they thought the each dimension: color—red, blue, and yel- animal was hiding behind. When touched ei- low; shape—boat, shoe, and teapot; size— ther shape resulted in the appearance of an small, medium, and large. In each trial, two animation. dimensions were relevant for matching (e.g., The test trials were then presented. Two shape and size) and one was irrelevant (color). 12-cm diameter circles were shown side-by- Each cue (color, shape, and size) occurs four side, one red and one blue. If children touched times as a cue that matches two items, four the blue circle, they heard the noise and saw 104 TOPICS IN LANGUAGE DISORDERS/APRIL–JUNE 2011 no animation. If they touched the red cir- Table 1. Performance Means, Standard Devi- cle, they saw one of the three animations ations, and Range for Delayed and Disordered (which appeared randomly). Then the next Groups for Measures of Language and Speech identical trial was presented. If children did not learn to touch the red circle, making ran- Delayed Disordered dom selections on 20 trials, the game finished. When children demonstrated that they had Quick Test of 20.7 (4.6) 20.6 (3.6) learned the rule (“touch the red circle to see Language 14–30 13–27 an animal”) five times consecutively, the rule Percent consonants 74.8 (9.6) 56.9 (12.4) changed. No instruction was given; children correct 55–88 29–77 Percent vowels 95.1 (5.4) 91.8 (6.3) just had to learn to touch the blue circle to see correct 75–100 73–100 the animations. If they did not derive the new Ratio of single words 75.9 (19.1) 73.2 (14.5) rule within 20 trials, the game finished. If they versus continuous 25–100 45–100 learned the rule, making five correct choices speech consecutively, they were presented with Inconsistency 13.9 (11.1) 16.1 (10.3) three shapes all of the same color (either all 0–30 0–30 red or all blue): a circle, a square, and a trian- gle, all of 8-cm dimension. They had to learn to touch the square. If they did not learn the new RESULTS rule, which was based on shape rather than color, the game finished. If they selected the Table 1 shows the means, SDs, and range square five times consecutively, they saw four for the delayed and disordered groups’ per- shapes (two triangles, a square, and a circle) of formance on language and speech measures. different colors (red, blue, green, or yellow). Each of these measures was used to compare The last rule children were asked to learn was the two groups using ANOVAs. There was no to touch the blue triangle, combining both significant difference in the two groups’ lan- shape and color. Throughout the experiment, guage scores on the Quick Test of Language; the assessors encouraged children by saying “I F(1, 44) = .021, p = .886. As all children had wonder which one the animals are hiding be- to perform within the normal range on the lan- hind” or “Where are those animals hiding?” guage measure to participate in the study, this The computer was programmed to code and result was expected. Data in Table 1 suggest store children’s performance, including how that the speech accuracy measures differen- many of the four rules were learned. tiated the groups. A two-factor ANOVA (two groups × consonants and vowels) showed a significant groups term; F(1, 44) = 22.483 p < Project design .001). Although both groups needed to per- Each task was analyzed using one or two form below the normal range on a standard- factor analysis of variance (speech delay ized assessment to be included in the study, group and speech disorder group × tasks) the result indicates that the delayed group with planned Bonferroni-corrected post hoc made fewer errors that the disordered group. tests where appropriate between and within More consonant errors were made than vowel groups. Parametric statistics were chosen be- errors, F(1, 44) = 411.72, p < .001, by the cause participant numbers gave sufficient sta- combined groups but the interaction between tistical power and comparison of tasks (re- groups and sound type (consonant or vowels) peated measures) was desirable to explore was also significant; F(1, 44) = 28.602, p < interactions (profiles of groups across tasks). .001. Post hoc one-way ANOVAs indicated Chi-square tests were used to examine cate- that although the children in the disordered gorical data. group were less accurate on consonants than Differentiating Speech Delay From Disorder 105 those in the delayed group, F(1, 44) = 29.979, the difference between the delayed group’s p < .001, the difference between the groups performance on the FIST 1 and 2 differed less in vowel accuracy was not statistically signifi- than that of the disordered group on the two cant; F(1, 44) = 3.607, p = .064. measures. The groups also did not differ on the mea- Also shown in Table 2 are data from the rule sure comparing single word versus continu- abstraction task. The table displays the num- ous speech. This measure, based on a ratio ber of children in each group who learned that is converted to a percentage for estab- no rules, and rules one, two, three, and four. lishing standard scores, compared whether More children in the delayed group learned the same 14 words were pronounced in the the first rule than did children in the dis- same way in picture naming and picture de- ordered group. These categorical data were scription tasks. The findings, based on broad analyzed using a 2 × 2 Chi-Square compar- transcription of children’s speech, indicated ing the number of children in each group that both groups pronounced around three- learning either no rules, or at least one rule 2 quarters of the words in the same way in both (χ 1 = 11.29, p < .001). The result indicates contexts. This finding shows less consistency that children with delayed phonological ac- of production between single words and con- quisition are more likely to derive nonlinguis- tinuous speech for children with speech im- tic rules than children with disordered phono- pairment than is indicated by normative data logical development. where the mean ratios for the same age range are between 84% and 87%. Similarly, there DISCUSSION was no difference in the two groups’ consis- tency of single word pronunciation when the Identifying appropriate treatment for chil- same words were named on three separate dren with speech impairment depends on occasions; F(1, 44) = .469, p = .497. Norma- knowledge of the impaired mental mecha- tive data (Holm, Crosbie, & Dodd, 2007) indi- nisms underlying the surface speech errors cate that once children are older than 3 years, (Stackhouse & Wells, 1997). The data de- their inconsistency of production of the same scribed here provided evidence concerning lexical items is below 10%. Table 1 indicates the cognitive-linguistic abilities of children that both groups of children with speech im- with speech impairment who performed be- pairment had higher inconsistency scores, al- low the normal range on a standardized though below the criterion level of 40% (Dodd speech assessment, in the absence of lan- et al., 2002). guage, neurological, sensory, or other ex- Table 2 presents the means, standard devi- planatory impairment. Two matched groups ations and range for delayed and disordered of 23 children each were compared on exec- groups for measures of cognitive flexibility utive function tasks of cognitive flexibility and and rule abstraction. A two-factor ANOVA nonverbal rule abstraction. One group had de- (groups × FIST selections 1 and 2) indicated layed speech development, as their speech er- no significant difference between the groups ror patterns were typical of younger children; when scores correct for FIST 1 and FIST 2 are whereas the other had disordered speech de- combined; F(1, 44) = 1.653, p = .205. There velopment, as they used at least one speech er- was a difference on the two FIST measures ror pattern that was atypical of any age group. with the combined group performing better Although the disordered group made more on FIST 1 than FIST 2; F(1, 44) = 77.937, consonant errors and different types of errors p < .001. Most importantly, there was a signif- in comparison to the delayed group, the two icant interaction, F(1, 44) = 5. 916, p = 0.019, groups did not differ on measures of language, indicating that the two groups performed vowel accuracy, difference ratio between differently across tasks. Table 2 indicates that single words versus continuous speech, or 106 TOPICS IN LANGUAGE DISORDERS/APRIL–JUNE 2011

Table 2. Performance Means, Standard Deviations, and Range for Delayed and Disordered Groups for Measures of Cognitive Flexibility and Rule Abstraction

Delayed Disordered

Cognitive flexibility task Flexible Item Selection Test 1 13.83 (1.5) 14.17 (1.2) (11–15) (11–15) Flexible Item Selection Test 2 10.74 (2.6) 8.74 (4.4) (4–15) (1–15) Difference scores: Flexible Item Selection Test 1 3.09 (2.2) 5.44 (4.1) minus Flexible Item Selection Test 2 (0–9) (0–13) Nonlinguistic rule learning task Number of children learning No rules 9 20 First rule 4 1 Second rule 6 2 Third rule 3 0 Fourth rule 1 0 consistency of word production. The results Few previous research studies have com- indicated that the disordered group per- pared delayed as opposed to disordered sub- formed less well than the delayed group on groups of functional speech disorder. Two two executive function tasks: they had poorer important factors have contributed to this cognitive flexibility and difficulty abstracting lack of research. There is no agreed terminol- nonlinguistic rules. The findings are now con- ogy. Some researchers use the terms as syn- sidered in more depth. onyms, or only ever use the term delay (e.g., Shriberg et al., 2005), whereas others make a clear distinction. It is only fairly recently, how- Similarities between the groups ever, that country-specific normative data on The speech of the groups of delayed and speech error pattern use, at particular ages, disordered children assessed were similar in have become available. Finally, the similari- important ways. Both groups made more con- ties between the groups, as defined here, are sonant than vowel errors and there was no striking: predominance of consonant errors group difference between the number of and consistency of word production. vowel errors made (although there was a non- significant trend for the disordered group to Differences between the groups make more vowel errors). The groups did Children classified as having a speech dis- not differ in their degree of inconsistency order performed less well than the delayed for single word production when asked to group on measures of consonant accuracy, name the same pictures three times, both cognitive flexibility, and rule abstraction. Ac- groups exhibiting around 15% inconsistency, curacy scores, like PCC in nonword repeti- which is about 10% more than typically de- tion at 3 years of age is a poor predictor of veloping children (Holm et al., 2007). Nor performance at 4 or 6 years (Dollaghan & did the groups differ in the extent to which Campbell, 2009). In contrast, Tyler, Lewis, their word production differed between sin- and Welch (2005) reported that consistency gle words and continuous speech. It should of errors accounted for 31.6% of the variance also be noted that both groups were selected in PCC change after intervention, indicating to have age appropriate receptive language. that the type of errors might be a more salient Differentiating Speech Delay From Disorder 107 marker than accuracy. Counting the number monthly for 10 to 12 months. Three children of consonant errors may then provide limited resolved their delayed acquisition of phonol- information about intelligibility. ogy by 33 months in that they performed One reason why children with disorder within normal limits on measures of phoneme might be less accurate than children with inventory, number of errors and type of er- delay is that disordered error patterns of- rors, and consistency. In contrast, the phonol- ten affect syllable structure as opposed to ogy of two children who had persisting diffi- phonemes (see Table 3 for a description of the culty was characterized by “smaller phonetic most frequently used of the disordered error inventories, less diverse and complex syllable patterns observed). If a child deletes all syl- structures, and lower PCC scores... Qualita- lable initial consonants (ICD), that must give tive variables that also appeared to be impor- rise to more errors than stopping of fricatives tant in predicting phonological outcomes at on the same set of words from the DEAP’s 33 months...included sound variability, atyp- phonology test. Table 3 lists three syllable ical error patterns, and little change in devel- structure processes for the disordered group opment across time” (Williams & Elbert, 2003; (marking consonant clusters with a bilabial p. 150). fricative, ICD, and assimilation (where only Cognitive flexibility is defined as an aspect one consonant marks all consonants in a syl- of human intelligence that allows children lable/word), whereas the delayed group ex- to integrate new information when learning hibited only limited final consonant deletion (De´ak, 2003). One perspective on children’s (of 1 or 2 phonemes e.g., /t/ and /k/), cluster acquisition of speech is that they listen to, reduction (where only one of the two mem- and gradually become aware of, the phonolog- bers would be counted as an error), and weak ical patterns around them (Williams, 1993). syllable deletion (where the number of weak For example, exposure to different syllables tested was limited). Accuracy, then, results in children using different error pat- may be an artifact of type of error pattern terns (e.g., see Zhu, 2002, for the acquisition rather than a clinically useful way of classify- of Mandarin). Phonological development re- ing speech impairment. quires flexible cognition as children need to Another way of characterizing the differ- dynamically construct and modify their “rep- ences between the groups tested, rather than resentations and responses based on informa- delayed and disordered, is as “late talkers” and tion (i.e., similarities, cues, relations) selected “long-term phonological delay.” Williams and from the linguistic and nonlinguistic environ- Elbert (2003) reported a longitudinal study of ment” (De´ak, 2003, p. 275). five children, identified as late talkers at 22 One previous study (Crosbie, Holm, and or 31 months of age, who were followed-up Dodd, 2009) compared three groups of

Table 3. Speech error patterns associated with phonological delay and disorder

Delay Disorder

Final consonant deletion (limited) Backing of bilabial and palatal stops [εd] /brεd/ Cluster reduction (2 member clusters) Word or syllable initial consonant deletion [if] /tif/ Fronting of velars and fricatives Stops substituted by fricatives [vuk] /buk/ Weak syllable deletion Clusters marked by bilabial fricatives [φi]/Tri/ Stopping of fricatives and affricates Vowel errors e.g., [wb] for /wεb/ Voicing errors Sounds preference e.g., all fricatives are [s] [sæn]/væn/ Intrusive vowels e.g., [ɑi:ε]/ε/ Extensive assimilation [bib]/pi/ 108 TOPICS IN LANGUAGE DISORDERS/APRIL–JUNE 2011

five-year-old children on the FIST (Jacques & The findings may provide evidence sup- Zelazo, 2001): typically developing, consis- porting the idea that speech impairment is tent speech disorder, and inconsistent speech often because of cognitive-linguistic factors disorder. The children with consistent speech rather than input and output limitations. The disorder performed significantly less well than cognitive processes involved in phonological the other two groups on both Selections 1 and acquisition may involve integrating informa- 2. The children with an inconsistent speech tion to derive phonological constraints us- disorder performed similarly to their typically ing the processes of rule abstraction, mem- developing peers. Poor performance on a ory, selective attention, flexible use of feed- measure of cognitive flexibility is not, then, al- back, and inhibition (Singer & Bashir, 1999; ways associated with severe speech disorder. De´ak, 2003). Intervention for disordered, as The findings reported here suggest that chil- opposed to delayed, speech development, dren who consistently use atypical error pat- should target, in that case, their impaired abil- terns also perform less well on the FIST 2 ity to derive rules and to integrate information than those who have delayed speech devel- to exhibit cognitive flexibility in rule abstrac- opment. Although the groups do not differ tion and implementation for both spoken and on their ability to identify one way in which written phonology. two pictures are similar, children with disor- der showed less cognitive flexibility than the Speech disorder, literacy, and delayed group. They were less able to iden- intervention tify a second way three items might be associ- Children with speech disorder do not ated, revealing a difficulty in shifting attention reorganize their phonological system with- between conceptual domains and inhibiting out intervention (Dodd et al., 2000), and their first choice. Lack of cognitive flexibility evidence supports treatment targeting the was also apparent in the rule-learning task. speech-processing deficit underlying a child’s Children with speech disorder who learned speech disorder as the approach that can re- the first rule usually persisted in its use. That sult in efficient systemwide change (Stack- is, having learned the rule that touching the house & Wells, 1997). For example, inter- red shape revealed the animations, they con- vention targeting phonological contrasts has tinued to push the red shape for many trials, been shown to be a more effective approach despite that action no longer revealing the an- for consistent disorder than a core vocabu- imation. The results clearly indicated that the lary therapy (Dodd & Bradford, 2000). Both disordered group learned fewer rules that the delayed and consistently disordered speech delayed group. impairment can be successfully treated by ex- An impaired ability to abstract and then im- plicitly teaching the phonological constraints plement the subtle constraints of the phono- that a child has failed to acquire (Howell logical system fits with evidence concern- & Dean, 1994; Gierut, 1998). Learning that ing the characteristics of disordered chil- phonemes contrast a difference in meaning dren’s errors (pervasive error patterns that and that these contrasts need to be pro- affect syllables like “all syllable final conso- nounced to avoid misunderstanding facilitates nants delete except nasals”) and their lack organization of phonemes into classes and of spontaneous change when no intervention phonotactically legal sequences (Grunwell, is available (Dodd, Zhu, & Shatford, 2000). 1997). The problem with this approach is that The results are also consistent with previous literacy difficulties characteristic of consistent research indicating that children with con- speech disorder may not be addressed by ther- sistent speech disorder later develop liter- apy that teaches spoken phonological rules acy difficulties, irrespective of whether their (Gillon, 2004). speech disorder has been resolved through Despite attaining age appropriate spo- intervention. ken phonology, many children with speech Differentiating Speech Delay From Disorder 109 disorder have difficulty acquiring written lan- phonological awareness); and phonological guage later and perform less well on phono- output using minimal pairs. Results showed logical awareness tasks (Gillon, 2004; Rai- significant enhancement of performance on tano, Pennington, Tunick, Boada, & Shriberg, two standard assessments of cognitive flexibil- 2004). One study (Nathan, Stackhouse, ity and phonological awareness. In addition, Goulandris, & Snowling, 2004) reported that the children’s mean PCC increased by 27% at age 6;9, 47% of children with a pure (SD 10), not differing statistically from a pre- speech disorder fell outside the normal range vious therapy trial (Dodd et al., 2008) where on standardized literacy assessments as com- the same amount of intervention, consisting pared with 28% of the control group. Chil- solely of minimal pair therapy, had been pro- dren with persistent and severe speech im- vided (PCC increase 23%, SD 13). Follow-up pairment were at risk particularly for literacy assessments, in 2 year’s time, will investigate difficulties. It might be argued that interven- the literacy acquisition of these two groups of tion for children with consistent speech dis- children. order should aim to address both spoken and written aspects of the children’s phonological CONCLUSION processing impairment by targeting deficits in cognitive flexibility and rule abstraction. The findings of the study reported here in- A recent study (Holm & Dodd, 2010) has dicate that children with speech delay differ provided preliminary evidence for a novel from those with consistent disorder both in approach to intervention for children with terms of severity and in the deficits in speech consistent speech disorder. Ten children re- processing that might underlie their speech ceived sixteen, 45-min, twice-weekly inter- difficulties. Previous research suggests that vention sessions. Each session was split into the two groups also differ in their profile of as- three 15-min activities focusing on rules and sociated abilities. Consequently, it seems im- patterns, with explicit links being made be- portant that intervention research begins to tween the three activities: pattern recog- compare the outcomes of different types of nition, sorting, and manipulation; language therapy for these two groups of children with rules and word patterns (e.g., plurality, tense, speech impairment.

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