Verb Selection and Past-Tense Morphology Crystal’S Criteria Revisited

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Top Lang Disorders Vol. 33, No. 2, pp. 152–164 Copyright c 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Verb Selection and Past-Tense Morphology Crystal’s Criteria Revisited

Brian Weiler

Research findings concerning verb-level influences on past-tense morphology carry implications for the careful selection of treatment targets. Using 6 of the broad criteria for “good verbs to choose” proposed by D. Crystal (1985) more than 25 years ago as a framework, this article summarizes some of the more recent research with a nod toward potential clinical applications. Specific semantic, frequency, developmental, phonological, and syntactic considerations for verb selection are discussed. Information is provided with respect to typical language learners and, when possible, children with language impairment. The article concludes with thoughts on using research findings to inform a guided approach to the selection of past-tense intervention targets. Keywords: David Crystal, intervention targets, lexical aspect, past-tense morphology, SLI, verb frequency, verb phonology, verb selection

IFFICULTY with the past-tense marking with language impairment (Windsor, Scott, & D of verbs beyond the typical time period Street, 2000). Accordingly, specific instruc- during which children optionally mark tense tion of past-tense morphology is a common is a defining clinical marker of children with sight on many treatment plans. primary language impairment (Rice, Tomblin, It behooves language interventionists to dif- Hoffman, Richman, & Marquis, 2004; Rice & ferentiate morphological instruction of the Wexler, 1996). Eventual proficiency with this past tense in a way that maximizes acquisi- structure in oral language may belie a per- tion of the target structure. Such differentia- sistent underlying linguistic vulnerability, as tion is commonly approached with a consid- evidenced by omissions of past-tense mark- eration of the elicitation or production task. ers in the written language output of children Tasks may span elicited imitation (e.g., repeat what I say) to open-ended questions (e.g., What did the boy do?) depending on the individual strengths and needs of a child at a given Author Affiliation: Department of Hearing and Speech Sciences, Vanderbilt University Medical point in his or her language development. Center, Nashville, Tennessee. What is less likely considered during the Preparation of the manuscript was supported planning of past-tense interventions is the by a Preparation of Leadership Personnel grant choice of which verbs to teach. More than (H325D080075; PI: Schuele), U.S. Department of Ed- 25 years ago, David Crystal (1985) wrote, ucation. The content is solely the responsibility of the author and does not necessarily reflect the official views “The question of deciding which verbs to of the supporting institutions, agencies, or foundations. teach first, in a language-teaching program, The author has disclosed that he has no significant rela- is too important to be left to chance” (p. 48). tionships with, or financial interest in, any commercial My concern is that, despite a quarter century companies pertaining to this article. of research literature to draw from, this de- Corresponding Author: Brian Weiler, MS, Depart- cision is still largely based on convenience, ment of Hearing and Speech Sciences, Vanderbilt if not chance. Verb targets quickly become University Medical Center, 1215 21st Ave South, Medical Center East 8310, Nashville, TN 37232 arbitrary when, for example, picture stimu- ([email protected]). lus cards or play routine manipulatives are DOI: 10.1097/TLD.0b013e31828f50b8 chosen without consideration of the specific 152

lexical factors known to impact the likelihood ful summary of relevant research findings re- of tense marking. Certain morphological cur- lated to past-tense marking from the interim ricula do offer some guidance. Notably, the period—four functional and two formal. The regular past-tense targets in the methods and more informed clinicians are about some of materials for Teaching Morphology Develop- the verb-level factors known to facilitate past- mentally (Shipley & Banis, 1989) are explic- tense marking, the more likely they are to use itly classified by the allomorphs /-t, -d, -əd/. information from empirical evidence to guide Other clinical materials, such as Months of their clinical decisions. Morphemes (Haskill, Tyler, & Tolbert, 2001), offer lesson plans with thematically appro- FUNCTIONAL CRITERIA priate verbs (e.g., cooking actions) without further discussion of expectations relative to Criterion 1 past-tense marking difficulty specific to the The verbs should express a clear physical, dy- target verb. For the most part, it appears that namic action (such as jump, kick, drink) and not clinicians are left to their own devices with be abstract, static, vague or mental (such as know, regard to verb target selection. Whereas se- do, have, feel, change). It should be noted that lection according to a thematic content unit these dynamic verbs can be classified into several (e.g., seasonal vocabulary or the zoo) may types—most importantly, into whether the action be appealing to both child and the clinician, has a clear beginning-point (open, knock), aclear end-point (kick, fall down), or has no clear-cut there is sufficient evidence to glean from the boundaries (play, run). (Crystal, 1985, p. 49) research literature to suggest that verb stimulus selection should be more judicious and The first of Crystal’s criteria for verb se- intentional. lection can be revisited in light of more Despite the scarcity of studies of evidence- recent research into lexical aspect considera- based practices related to verb target se- tions of children’s past-tense productions. As- lection in morphological interventions, the pect, generally speaking, refers to “the way research literature does offer findings that sup- the grammar marks the duration or type port evidence-based principles of language in- of temporal activity denoted by the verb” tervention. These principles can be broadly (Crystal, 2008, p. 38). In English, an aspec- aligned with the essential criteria for careful tual distinction is made, for example, between verb selection established by Crystal (1985). progressive (e.g., I was sleeping) and nonpro- Because of the centrality of verbs to sen- gressive (e.g., Islept). Lexical aspect relates to tence structure development, efforts should the inherent semantic and temporal proper- be made, according to Crystal, to minimize ties of situations described by individual verbs failure lest children be “put off by verbs,” and their adjuncts (Li & Shirai, 2000). Adjuncts which, in turn, could slow language develop- are the “optional or secondary element(s) in ment. Therefore, his criteria for verb selection a construction” such as adverbs and modi- reflect what could generally be considered to fiers (Crystal, 2008, p. 12). According to Smith be the most facilitative for learning. The orig- (1997), the presence or absence of the state, inal criteria were divided into two categories: durative, and telic properties determines clas- Functional and Formal. The Functional crite- sification among the four lexical aspect cat- ria relate to the contexts within which the egories, which had been established earlier verbs are used (i.e., their functions), whereas by Vendler (1967): state, activity, accomplish- the Formal criteria reflect the structural char- ment, achievement. These relationships are acteristics (pronunciation, grammar, mean- illustrated in Table 1. ing) of the verbs themselves (i.e., their forms). The primary distinction between the lexical The purpose of this article was to expand aspect categories of activity and accomplish- the current evidentiary basis of six of Crystal’s ment concerns the telic property. Telicity dis- criteria for verb selection with a clinically use- tinguishes verbs that can be characterized as

Table 1. Lexical aspect categories

Category Properties Example

State [ + durative] [ − dynamic] [ − telic] I wanted it. Activity [ + durative] [ + dynamic] [ − telic] She rode the horse. Accomplishment [ + durative] [ + dynamic] [ + telic] He tied his shoes. Achievement [ − durative] [ + dynamic] [ + telic] Sheblewoutthecandle.

Note. [ + durative] = event takes time to occur; [ − durative] = event occurs instantaneously. [ + dynamic] = event involves motion; [ − dynamic] = event is a state. [ + telic] = event has a deﬁned endpoint; [ − telic] = event has an undeﬁned endpoint. From “Interaction of Lexical and Grammatical Aspect in Toddlers’ Language,” by B.W. Johnson and M. E. Fey, 2006, Journal of Child Language, 33, pp. 419–435, which drew on the work of The Parameter of Aspect (2nd ed.), by C. S. Smith, 1997, Dordrecht: Kluwer Academic Publishers. Adapted with permission of the publisher.

having an endpoint from those that have no tween achievements and activities relates to specified endpoint. For example, the phrase, both telicity and duration. Whereas achieve- walk to the park, suggests an endpoint and ments are bounded by an endpoint and in- would be characterized as an accomplishment stantaneous (e.g., He popped the balloon), with the temporal feature of being telic ( + activities are unbounded and gradually occur- telic). Conversely, the phrase, stroll in the ring (e.g., He rode his bike). Leonard, Deevy, park, does not suggest an endpoint and would et al. (2007) found that, in an elicitation probe, be characterized as an activity with the tempo- 3-year-olds with typical language mark regular ral feature of being atelic ( − telic). Drawing past tense with greater accuracy for achieve- on the lexical aspect categorical framework ments than activities (d = .72). The facilita- initiated by Vendler (1967) and refined by tive advantage of achievements over activities Smith (1997), Johnson and Fey (2006) exam- observed in children with typical language ined young children’s use of past-tense mor- skills in the study was not seen, however, in phology in reference to events that were ei- 5-year-old children with language impairment ther bounded by an inherent endpoint (e.g., (d = .15). She pushed a train onto a box)orunbounded To specifically address whether the dura- by an inherent endpoint (e.g., She pushed a tion involved in reaching an event’s endpoint train in circles). They found that typically influences past-tense marking, Weiler and developing 2-year-olds imitated past-tense Schuele (2011) compared responses from typ- morphology with higher accuracy for verb ically developing children to a past-tense elic- contexts bounded by an endpoint (i.e., ac- itation prompt across telic verbs that differed complishments) than unbounded by an end- on the durative property (i.e., achievements point (i.e., activities) (effect size: d = .36). The vs. accomplishments). Comparable overall ac- experimental task was replicated with similar curacy in past-tense marking was found across results in a case study with a 4-year-old with the two lexical aspect categories under inves- specific language impairment (SLI; Johnson & tigation, χ 2(1) = .156, p > .50. Considering Morris, 2007). this finding alongside the aforementioned in- Additional investigations into the potential vestigations of lexical aspect and past-tense interaction between lexical aspect and gram- marking, it appears that typical preschool- matical tense marking have addressed the telic ers are better able to exploit their past-tense and durative properties. The term “durative,” morphology skills with verbs that describe an within a consideration of aspect, refers to “an event with a specified endpoint but are rela- event involving a period of time” (Crystal, tively uninfluenced by whether that endpoint 2008, p. 159). The aspectual distinction be- was reached instantaneously or gradually.

Although current findings for children with Verb frequency also appears to influence language impairment are mixed and limited, regular past-tense marking. In a study of past- clinicians can still apply evidence from typ- tense marking in children with and without ical development to inform past-tense inter- SLI, Oetting and Horohov (1997) identified ventions. Specifically, Crystal’s initial criterion frequently and infrequently occurring verbs that verbs taught early in the development of inflected for past tense from a child corpus a language structure should express “a clear of spontaneous speech (Hall, Nagy, & Linn, physical, dynamic action” can be refined to 1984). The results of their productivity probe favor those verbs and/or verb phrases that showed that children with SLI as well as nor- represent a completed action with a defined mally developing, mean length of utterance endpoint. The application of this evidence- (MLU)-matched peers were significantly more based principle might extend to the selec- likely to mark past tense on frequently oc- tion of past-tense elicitation stimuli such as curring (vs. infrequently occurring) inflected “This boy is riding his bike to school. What verbs requiring the allomorphs /-d/ or /-t/ did he do?” over similar stimuli that are un- whose bare stems end in nasal, stop, and bounded by an endpoint such as “This boy fricative consonants (e.g., climb, hug, jump, is riding his bike. What did he do?”Re- cough; ds (SLI) = .84 [/-d/], .86 [/-t/]; ds search findings indicate that the first stimulus (MLU-matched) = .73 [/-d/], .48 [/-t/]). The may be more prototypical and salient, from difference in past-tense marking according to a child’s perspective, of a completed event child frequency value was not observed for and therefore more likely to elicit accurately those verbs whose bare stems end in liquids, a response marked for past tense. Picture glides, or vowels and require the /-d/ allo- prompts may not fully capture the “verbness” morph (e.g., pour, smell, cry), d (SLI) = .46; of such an event because of their visually static d (MLU-matched) =−.59. and two-dimensional presentation (Klimacka When instructing regular past-tense mor- & Brunger, 1999). Instead, presenting short, phology, at least for verb stems ending in and preferably wordless, video clips or using consonants, a consideration of the verb’s in- toy manipulatives to “act out” the event may flected frequency across child language sam- more realistically convey the completion of an ples appears merited. Frequently occurring action. Given the unique challenges children targets are apt to be more familiar and with language impairment have in acquiring salient to the child, thereby allowing for past-tense morphology, clinicians should con- greater focus on the morphological rule for sider stimuli that most clearly convey the con- past tense instead of teaching verb mean- clusion of an event or situation. Doing so will ing. Language interventionists can access age- help ensure that the grammatical aspect of specific, child-inflected verb frequency values past perfective tense is made explicit to the culled from more than 5,000 English tran- child. scriptions from the CHILDES (Child Language Data Exchange System) database available at Criterion 2 http://childfreq.sumsar.net/ (B˚a˚ath, 2010). In addition to frequency counts derived The verbs should be familiar to [the child]. from child corpora, verb familiarity can also (Crystal, 1985, p. 49) be considered relative to the individual child’s The frequency with which children use experiences. There is inherent variability in verbs inflected for past tense provides a win- children’s familiarity with verbs, depending dow into their relative familiarity with those on the individual child’s home and school en- verbs. In other words, clinicians can be rea- vironments and routines. To maximize the sonably confident that more frequently pro- familiarity of verb targets for a grammati- duced verbs should, by extension, be more cal intervention such as past-tense morphol- familiar to children. ogy, clinicians are advised to solicit input

from parents and teachers whenever possi- productive use of 102 early-emerging verbs, ble. Interviews to inquire about familiar rou- or “action words” listed on the form. Re- tines, termed routines-based interviews (RBI; sponses from more than 1,000 parents were McWilliam, Casey, & Sims, 2009), are one compiled in a public, Web-based database, vehicle of gathering information about the available at http://www.sci.sdsu.edu/lexical types verbs apt to be familiar to a child. The (Dale & Fenson, 1996). By the age of RBI is a semistructured interview compris- 30 months, the vast majority of verbs (97 of ing questions about the child’s daily routines, 102) were reportedly produced by at least half from the beginning to the end of a typical of the children. In addition, a majority of the day. McWilliam et al. (2009) noted that “the verbs listed on the inventory (71) were report- stress on routines is because of the behavioral- edly produced by at least 80% of 30-month- ecological notion that routines are the con- olds. text in which the need for intervention is ‘au- As a result of these findings, specific verb- thentically’ determined” (p. 225). The fam- level information available from the CDI lexi- ily responses to the RBI can then be used cal development norms can be more system- to plan interventions. An application of the atically applied to the selection of treatment RBI approach to a morphological interven- targets relative to their emergence in the ex- tion targeting past tense may thus extend to pressive lexicon. For example, whereas a clin- the selection of “authentic” or “ecologically ician might intuit that a verb such as skate is valid” verbs familiar to the child. For exam- early emerging, results from the CDI database ple, if a mother reported that a routine con- suggest that less than half of all 30-month- versational topic with her child related to the olds have produced this word. Certainly, a child’s involvement with swimming lessons, 30-month-old would not be a likely candidate then verbs such as float, dive, dip,anddunk for past-tense intervention. Instead, the point might emerge as logical candidates for inter- is that, for children for whom morphological vention targets. interventions are appropriate, verbs that have been a part of their productive lexicon for a Criterion 3 longer period of time may be more amenable The verbs should be easy to learn, in the sense to treatment. Such verbs and their meanings that they are among the earliest verbs to appear in are likely to be more deeply ingrained in the the normal language acquisition process. (Crystal, child’s linguistic repertoire. Therefore, the 1985, p. 50) child’s cognitive and linguistic resources can The classic observational studies of Bloom potentially be allocated more to the learning (1991) have provided valuable insight into of past-tense morphology and less to the learn- the acquisition of verbs across categories of ing of new verbs. verb relations. Bloom’s study of four toddlers Like Bloom’s (1991) seminal early work, ranging in age from 18 to 25 months indi- Brown’s (1973) observational studies offer cated, for example, that action verbs (e.g., valuable insight into the normal language ac- Open de buttons) appear before state verbs quisition process. Considering more recent (e.g., I hear childrens). Beyond such categor- studies alongside Brown’s findings can build ical information, however, knowledge of chil- on the foundation he established. For exam- dren’s acquisition of specific verbs in their ple, Brown listed irregular past-tense verbs as expressive lexicon has emerged more re- developing fifth sequentially among the 14 cently. In particular, a normative study for grammatical morphemes he analyzed. Irreg- The McArthur-Bates Communicative Develop- ular past-tense forms thus are expected to ment Inventories: Words and Sentences (CDI; appear before regular past-tense forms (listed Fenson et al., 2007) yielded the proportion ninth) in Brown’s account of morphological of children at each month between 16 and development. As discussed later, however, 30 months of age whose parents reported the use of Brown’s sequence as the sole basis

for intervention goals, particularly for mastery Heeding Crystal’s (1985) advice to teach (not just marking) of irregular past-tense mor- verbs according to the normal acquisition phology, invites concern. Although certain ir- process, language interventionists are encour- regular past-tense verbs appear frequently in aged to reference the ages of irregular past- the language of children by 3 years of age, it is tense mastery for specific verbs reported commonly thought that early-occurring forms by Shipley et al. (1991) in order to avoid such as ate and broke are learned by rote as exhausting valuable teaching time correct- whole, unanalyzed units. Shortly thereafter ing otherwise age-appropriate overregulariza- in development, as children begin actively tions. Concerning the irregular past tense, to deploy regular past-tense rules, overregu- Brown’s order of acquisition should serve as larizations such as eated and broked appear a starting point but not as a roadmap for mor- (Marcus et al., 1992). This U-shaped devel- phological intervention. Whereas normal de- opmental pattern of early accuracy, followed velopmental sequences may “represent the by subsequent inaccuracy, is completed only easiest or even the necessary order” of ac- later in language development when children quisition, it is important that clinicians not relax an overreliance on the regular past rule “take a description of the course of nor- to produce correct irregular past forms con- mal acquisition as a prescription for the way sistently. language must be taught” (de Villiers & de What does this have to do with verb se- Villiers, 1978, p. 270). lection for past-tense interventions? Most im- Criterion 4 portantly, the developmental timeline within which children master the irregular past tense The verbs should be frequent in adult language. (i.e., when they cease to overregularize) ap- (Crystal, 1985, p. 50) pears to vary quite significantly according to This recommendation for verb target selec- the verb. Failure to recognize this clinically tion has found some empirical backing in the may result in unnecessary training of verbs in past-tense experimental literature. Notably, children younger than the age of mastery indi- Marchman, Wulfeck, and Weismer (1999) cated by normal development. For example, examined how the frequency of adult us- Kuczaj (1977) found that overregularization age of specific verbs inflected for past tense errors on irregular past-tense verbs are pro- might impact children’s responses on a past- duced by children who have already demon- tense elicitation task. Frequency values for strated stable control of the regular past-tense past-tense forms of verbs were taken from rule. Moreover, the acquisition of irregular adult, White, middle-class samples (Hall et al., past-tense forms can persist until the age of 1984) and were divided into low- and high- 6 years or beyond (Menyuk, 1963). Indeed, frequency categories. Results from the elici- using 80% accuracy in a sentence comple- tation task showed that children with both tion as criterion, Shipley, Maddox, and Driver typical and impaired language skills were less (1991) found that among typical language likely to mark past tense on low-frequency learners, many irregular past-tense forms were regular and irregular verbs. Both groups, but not “mastered” until 6, 7, or 8 years of age. particularly children with SLI, were more In fact, several verbs continued to be com- likely to omit past-tense morphology on those monly overregularized through the age of 8; verbs that were both low in adult lexical 11 years. Irregular verbs most prone to a delay frequency and whose bare stem ended in an in the shift from being overregularized to be- alveolar stop consonant (e.g., build, mend). ing marked accurately according to the adult Incorporating Crystal’s (1985) evidence- language were those that require a final conso- backed advice into clinical practice can be nant change from /d/ to /t/ (e.g., build, send, accomplished through accessing adult lexical bend; Shipley et al., 1991). frequency values via the CHILDES Parental

Corpus (Li & Shirai, 2000; MacWhinney, ending in alveolar stop consonants that are 2000). This corpus consists of utterances legitimately zero-marked for past tense (e.g., produced by parents, caregivers, and exper- hit, bid, cut). Interestingly, the omissions of imenters in largely child-directed language past-tense marking among children with SLI, contexts (e.g., dinner table talks, activities of when compared with those with normal lan- free plays, and storytelling). Frequency of oc- guage, were even more highly predicted by currence values for more than 24,000 words the stem final phonology of the verb. This types from this corpora, including verbs in- finding was particularly evident among verbs flected for past tense, can be found at http:// with low adult-inflected frequency values childes.psy.cmu.edu/derived/parentfreq.cdc. (Marchman et al., 1999). The effect of such an interaction between FORMAL CRITERIA more than one verb-specific characteristic Criterion 5 (e.g., stem final phonology and frequency) on the likelihood of past-tense marking was The verb should have a pronunciation which also observed by Oetting and Horohov (1997). presents as few problems as possible. (Crystal, Results from an elicitation probe revealed 1985, p. 50) that children with SLI and younger controls Whether because of articulatory ease, matched on MLU were significantly more phonotactic probability, neighborhood den- likely to mark regular past tense on low- sity, or some combination of these or other frequency inflected verbs ending in a liquid factors, the fact that the phonological prop- or vowel (e.g., pull, tie) than low-frequency erties of verbs impact past-tense marking ac- verbs ending in consonants requiring a /d/ or curacy is well represented in the literature. /t/ allomorph, ds (SLI) = .78 [/d/], .64 [/t/]; ds Whereas some phonological characteristics (MLU-matched) = 1.40 [/d/], .94 [/t/]. Such a are facilitative, others appear to pose, as Crys- difference for high-frequency inflected verbs tal notes, “problems.” Whether or not the na- was not significant. Eyer and Leonard (1994), ture of such problems rests purely in “pronun- in a case study of a past-tense intervention ciation,” or, more likely, in general linguistic for a child with SLI, also reported on an ap- competence, is beyond the aim of this article. parent advantage for marking past tense on Instead, the following summarizes some of the verbs whose bare stems end in vowels. They research findings on phonological influences found that the child’s limited use of regular on past-tense marking. past-tense inflections and overregularizations Recognition of the allomorphic variations occurred on verbs such as dry and blow. of regular past-tense morphology, /-t, -d, -əd/, Another potentially influential variable is is expected of speech–language pathologists, the phonological composition of stem verbs particularly those serving children. What may marked for irregular past tense with respect be less familiar to clinicians are research find- to vowel change (e.g., fly → flew). The con- ings showing that the likelihood of past-tense trast of the vowel in the verb stem form marking may not be equally dispersed across and the vowel in the inflected form can be the three allomorphs. Importantly, bare stem viewed according to which vowel is dominant verbs ending in the alveolar stop consonants and which is recessive. Dominant vowels may /t/ or /d/, and thus taking the syllabic marker be considered more phonologically salient in /-əd/ if regular (e.g., paint-ed, land-ed), were that they have a specified place of articulation less likely to be marked for past tense in an (e.g., + back, + high, + low, or + round), elicitation probe than bare stem verbs ending are diphthongs (e.g., / /, /ei/), or have high in a phoneme other than /t/ or /d/ (Marchman, phoneme frequencies (Stemberger, 1993). In 1997; Marchman et al., 1999). Verb stems contrast, recessive vowels are less phonolog- ending in /t/ or /d/ may be problematic for ically salient in that they have an underspeci- children because there are bare stem verbs fied place of articulation (e.g., − back, − high,

− low, or − round), are monothongs (e.g., tense forms) than their performance on verbs / /, /ε/), or have low phoneme frequencies. from “unfriendly neighborhoods.” In some cases, the dominant vowel is con- Finally, the phonotactic probability of past- tained within the stem verb such as in the tense endings appears to influence children’s uninflected verb throw. When the verb under- command of past-tense morphology. Phono- goes a vowel change during past-tense inflec- tactic probability relates to the likelihood that tion, the vowel may then become recessive, the phonetic content of inflected verbs could such as in the verb threw. For other verbs, occur in monomorphemic words. For exam- the stem vowel is recessive and becomes ple, the [ld] blend in rolled also can occur in dominant only when inflected for past tense monomorphemic words such as cold. On the (e.g., come → came). Testing the hypothe- contrary, the [Nd] blend in hanged does not sis that dominant vowels represent the “op- occur in single-morpheme English words. Re- timal phonological form” and should there- search has shown that children with SLI, but fore “be more easily produced,” Marchman not younger language ability-matched con- (1997, p. 287) found that children were in- trols, are less likely to use regular past-tense deed more likely to mark past tense on past endings when the phonetic context does dominant (vs. stem dominant) vowel change not appear monomorphemically (d = .70; verbs. In other words, past-tense marking was Marshall & van der Lely, 2006). Extending more likely to occur when the vowel shift re- these findings by controlling for previously flected a movement of stem recessive (come) learned inflected forms, Leonard, Davis, and to past dominant (came). Those verbs with Deevy (2007) used novel verbs referring to stem dominant vowels that ended in alve- novel actions and found that children with SLI olar stop consonants (e.g., bite)werethe marked past tense more frequently on verbs most unlikely to be marked for past tense with high (vs. low) stem and inflected phono- use. tactic probabilities (d = .98). This phonotactic Neighborhood structure has also been con- probability effect on past-tense marking was sidered with respect to phonological fea- not observed in the MLU- or age-matched con- tures potentially impacting past-tense mark- trol groups. ing. Neighborhood structure is determined by the frequency of co-occurrence of certain Criterion 6 phonological patterns in words (Marchman Lastly, there is the question of which syntac- et al., 1999). Verbs that belong to the same tic considerations we should take into account. neighborhood are those that share the same (Crystal, 1985, p. 50) final vowel or vowel–consonant phonemes. When considering past tense, the verbs shake If the goal of a grammatical intervention and take are good neighbors or “friends” in targeting past-tense morphology production that their shared bare stem ending holds up in is to aid children in becoming better language the past tense (shook, took). On the contrary, users, then the grammatical form, in and of shake and bake are enemies in the past-tense itself, should rarely be the only component neighborhood because their inflected forms of language targeted (Fey, Long, & Finestack, do not share final vowel–consonant phonol- 2003). In considering verbs to target, Crystal ogy (shook, baked). It turns out that being (1985) noted that “the most important factor a good neighbor is indeed advantageous, at is that verbs should allow an easy transition least insofar as past-tense marking. Marchman to the next stage of syntactic development” (1997) found that children with typical lan- (p. 50). By the elementary school years, typi- guage skills were more likely to mark past cally developing children and, to a lesser ex- tense in an elicitation probe on verbs from tent, children with language impairments use “friendly” neighborhoods (i.e., more shared a variety of complex sentence structures in co-occurrences between bare stem and past- spoken language (Marinellie, 2004; Schuele

& Dykes, 2005; Tyack & Gottsleben, 1986). that the child produce the subject of the To limit past-tense intervention to simple- clause (interchange b) and not just the verb sentence productions, therefore, would rep- phrase and its complements or adjuncts (inter- resent a failure to “make use of grammati- change a). cal constructions in pragmatically felicitous Examiner–child verbal interchanges contexts” (Fey et al., 2003, p. 5). In other (a) E: Here the girl is planting the flowers. words, clinicians are cautioned against assum- Now she is done. ing that proficiency with past-tense morphol- E: Tell me what she did. ogy in simple sentences will extend to more C: Plant flowers. complex sentence structures without train- (b) E: Can you start with she? ing. On the contrary, evidence suggests that a C: She planted flowers. potential tradeoff exists between increasingly E: Great story. complex sentence structures (e.g., finite com- The findings of this study indicated that plement clauses such as John remembered responses to the Past Tense probe that in- where Sue hid) and accuracy in past-tense clude only the verb phrase with an unmarked morphology (Owen, 2010; Owen & Leonard, verb are not consistently construed as oblig- 2006; Weiler & Schuele, 2012). Consequently, atory past-tense contexts for preschool chil- target selection for past-tense interventions dren. For the majority (65%) of interchanges, should be made with consideration of those initial subjectless responses with unmarked verbs that can take a clausal complement. verbs that were reprompted by the examiner Complement-taking mental or cognitive-state to include a response with a third person sub- verbs such as wonder, know, remember,and ject also included a main verb marked for past think (e.g., He wondered where Mary would tense. This finding is consistent with a similar go) are pragmatically useful target candidates. study of third person present tense responses One final note related to syntactic consid- from the Third Person Singular Probe of the erations in past-tense elicitation procedures TEGI (Eisenband, Schuele, & Barako Arndt, applies to all verbs. Elicited production tasks 2011). Thus, child responses that include an and elicited imitation tasks have been offered unmarked lexical verb without a subject may as alternatives to spontaneous language sam- provide insufficient information about the ples, particularly when a specific and/or infre- child’s ability to mark tense in obligatory con- quently occurring structure, such as the past texts. Rather, the child’s underlying structure tense, is of interest. In an elicited language may be an utterance with an imperative or an production task, the examiner sets up a con- elided auxiliary “do” syntactic structure. To text, using verbal and nonverbal prompting, ensure that the syntactic frame obligates past- that creates a condition for the production of tense morphology, clinicians should set up, the target structure (Thornton, 1996). Essen- and prompt as needed, an elicitation context tial to this condition is the prompting for a syn- that requires that the child utterance include a tactic frame that obligates the inflected verb subject. Doing so should more reliably reflect form. The elicitation task must make it likely skill in past-tense marking. that children will attempt the target of interest. An investigation by Barako Arndt, Weiler, CONCLUSION Eisenband, and Schuele (2012) examined the necessary components in a child’s response The principles for verb target selection to ensure a valid measure of grammatical per- proposed by Crystal (1985) almost 30 years formance on the Past Tense probe of the Test ago have proven prescient when consid- of Early Grammatical Impairment (TEGI; Rice ered alongside more recent research on & Wexler, 2001). They questioned whether acquisition of past-tense by children with and a valid measure of linguistic skill requires without SLI. The broad Functional and Formal

categories he outlined, and the individual cri- ments in Table 2). Far from acting in isolation, teria therein, can serve as a helpful framework however, the myriad of potential verb-level for considering the clinical utility of emergent inﬂuences on past-tense marking likely ﬁndings (see summary outline of key ele- interact in complex and dynamic ways. The

Table 2. Examples of application of Crystal’s criteria to the selection of past-tense intervention targets

Factor More Facilitative Less Facilitative

Lexical aspect1,2 + Telic − Telic He chewed up a raisin. He chewed gum. She crawled to her daddy. She crawled around the yard. Inflected verb High frequency verbs4 ending in Low frequency verbs4 ending in frequency—Child3 nasals, stops, or fricatives and nasals, stops, or fricatives and marked with /t/ or /d/. marked with /t/ or /d/ He opened the door. He plugged the cord in. She closed the door. She sneezed loudly. Inflected verb High frequency regular and Low frequency regular and irregular frequency—Adult5 irregular verbs4 verbs4 He baked a cake. He peeled an orange. She fell off the chair. She sent a letter. Verb stem ending5,6 Phoneme other than /t/ or /d/ Alveolar stops /t/ or /d/ He broke the vase. He painted a picture. She played checkers. She sat down. Verb stem ending × Low frequency verbs4 ending in Low frequency verbs4 ending stops, inflected verb a vowel or liquid and marked nasals, or fricatives and marked frequency—Child3 with /d/ with /t/ or /d/ He filled the cup. He waved goodbye. She cried for her mommy. She danced in circles. Irregular past-tense vowel Past dominant7 Stem dominant7 change6 He ride → rode the horse. He lead → led the race. She find → found the keys. She grow → grew an inch. Neighborhood structure6 Verbs from “friendly” Verbs from “unfriendly” neighborhoods6 neighborhoods6 He feed → fed the horse. He eat → ate an apple. She bleed → bled a little. She meet → met the teacher. Phonotactic probability Monomorphemically legal Monomorphemically illegal of past tense ending8 He tossed the ball. He hugged his sister. She packed her bag. She fished for trout. Lexical aspect × verb Activity category and Activity category and obstruent stem ending9 nonobstruent stem stem He chewed on the rattle. He skipped on the grass. She crawled in circles. She jumped around the lawn.

Note. 1Johnson & Fey, 2006; 2Leonard et al., 2007; 3Oetting & Horohov, 1997; 4Hall, Nagy, & Linn, 1984; 5Marchman, Wulfeck, & Weismer, 1999; 6Marchman, 1997; 7Stemberger, 1993; 8Marshall & van der Lely, 2006; 9Johnson & Morris, 2007.

likelihood of children’s use of past-tense mor- ence might be differentiated according to the phology in obligatory contexts may best be empirical application of Crystal’s criteria dis- explained by the additive influence of several cussed in this article. A research-based guided properties of target verbs (Owen, 2010). For approach to the selection of past tense targets example, past-tense morphology has been would be more accessible than expecting in- shown to be influenced by a combination of dividual clinicians to sift through numerous verb-level phonological and lexical aspect fac- research articles to identify relevant findings. tors (Johnson & Morris, 2007). Accordingly, a Similar to how a clinician might use 40,000 facilitative framework for learning past tense Selected Words: Organized by Letter, Sound, might entail the clinician selecting verbs with and Syllable (Blockcolsky, Frazer, & Frazer, phonologically simple stem endings (i.e., a 1987) to inform his or her phonological in- liquid or vowel) and using them in action terventions, examples of past tense targets by contexts with clear endpoints (Oetting & criterion category could be selected from a Hadley, 2008). more exhaustive reference list and then cus- The obvious challenge facing clinicians, in tomized on the basis of the individual needs, light of growing research in this arena, is goals, interests, or routines of the child. how best to incorporate complex findings Interventions targeting delayed morpho- into their daily practice. Clinicians may ben- logical structures such as past tense, when efit from a guiding reference for stimulus se- targeted within a functional communica- lection for past-tense interventions that builds tion context, are indicated by the literature on the foundation established by Shipley and (Oetting & Hadley, 2008). If the primary pur- Banis (1989) in their methods and materials pose of evidence-based practice is to “help for Teaching Morphology Developmentally. clinicians make well-informed decisions about Such a treatment reference might group verb treatment selection,” then failure to carefully targets for past tense (and, ideally, other mor- consider past-tense targets is to neglect an im- phemes and syntactic structures) according portant body of evidence (Lof, 2011, p. 193). to what current research indicates is more or This is consistent with Crystal’s (1985) coun- less facilitative of the target structure for typ- sel that “the question of deciding which ical language learners and, if different, chil- verbs to teach first, in a language-teaching dren with language impairments. Table 2 pro- program, is too important to be left to vides a cursory illustration of how such a refer- chance” (p. 48).

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