INT. J. LANGUAGE & COMMUNICATION DISORDERS, 1998, VOL. 33, SUPPLEMENT

PROCESSING LOAD AND THE EXTENDED OPTIONAL INFINITIVE STAGE

Karen Brunger and Alison Henry

School of Behavioural and Communication Sciences University of Ulster, Newtownabbey, BT38 8TU

Spontaneous language data fiom fifteen language-impaired children in the Extended Optional Infinitive stage of morphosyntactic development are examined with respect to processing load. Clauses with a target finite verb form are categorised according to finiteness and their preverbal constituents. Patterns of occurrence are discussed with regard to the Optional Infinitive framework itself and the implications for remediation.

Introduction

Verb morphology and auxiliary/copular omission in early child Enghsh, traditionally seen as separate developmental phenomena, have recently been re- characterised as the surface features of an underlying non-finite matrix clause pattern, known as the Optional Infinitive (09 stage (Wexler 1994). ‘Optional’ refers to the fact that for a certain period, usually between approximately two and four years of age, non- finite clauses commonly occur alongside adult-like finite structures, the proportion of the former decreasing in favour of the latter as children get older. The 01 framework is now also being posited as an account of the morphosyntactic difficulties of specific language impaired (SLI) children. They appear to go through an Extended Optional Infinitive (EOI) stage, which is like the 01 stage in its features only much longer-lasting and in some cases never completely resolving (Rice el ul. 1995).

F’revious accounts of SLI children’s morphosyntactic difficulties either posited problems in their underlying grammatical capabilities (i.e. difficulties forming implicit rules fiom the language input features) (Gopnik and Crag0 1991) or general input processing difficulties (i.e. low phonetic saliency of inflections and auxiliaries etc. combined with the need to formulate rules from them results in a processing overload) (Leonard et ul. 1989). The EOI account however is based very much in a contemporary Universal Grammar (UG) theoq~ of language acquisition and the continuity approach which require that the underlying grammatical representations of children (at least those developing language nonnally) will correspond with UG‘s proposed structure. Hence inflectional processes, instead of arising from matching certain morphophonological forms with morphosyntactic features at quite a late stage in encoding a message, are thought to operate at a deeper level and to interact closely with movement mles. Examined within this fiamework, SLI children’s grammars appear remarkably similar to those of younger children in the 01 stage, (Rice and Wexler 1996, Rice e l al. 1995).

Optional Infinitives and the Extended Optional Infinitive stage The 0 1 account of normal language acquisition highlights the fact that child

utterances such as ‘the boy go to school’, ‘then he jump over the fence’, ‘that going fast’,

1368-2822/98 $12.00 0 1998 Royal College of Speech & Language Therapists

Developmental speech and language processing 423

‘that girl happy’ and ‘we not like cabbage’ all lack one significant syntactic characteristic in their underlying structure, i.e. finiteness (tense and agreemeat marking), which is compulsory in the corresponding adult clauses and represented by ‘a’, ‘4, ‘is’, ‘is’ and ‘do’ respectively. However there is a developmental period when such non-finite clause use is eccompanied by equivalent finite clauses whose adult-like properties, rather than being a matter of coincidence, indicate a howledge of the processes associated at an underlying level with inflection. For instance they almost invariably include coma agreement (utterances such as ‘I goes’, ‘the children runs’ and ‘we am running’ rarely occur) and the verb movement processes associated with the finiteness feature become operational. In UG movement processes cause the finite verb form in questions and negatives to move ‘upward’ in the phrase structure tree but because English does not allow sentences like ‘he runs not’ and ‘runs the boy?’ an auxiliary is imerted to carry the finiteness features of tense and agreement to give ‘he does not NU’ and ‘is the boy running?’ In children acquiring language n o d y (NL) and in SLI children there is an extremely strong association between verb movement and finiteness and between lack of verb movement aad non-finiteness (Wexler 1994, Rice et al. 1995). There is very little evidence of finiteness without verb movement e.g. ‘he not runs’, ‘they not are laughing’ or non-finiteness with verb movement, e.g. ‘run he?’, ‘he run not’, and children also seem to know that finite lexical verbs m o t undergo movement, e.g. ‘runs he?’, only applying movement when they are able to enlist the auxiliary or copular to cany finiteness.

Despite such ‘knowledge’ of finiteness, children continue to use non-finite clauses alongside finite clauses for some time as if they were distinct sides of an optional setting. However optionality is a feature not allowed by UG so although the existence of an 01 stage is well-established, its underlying nature remains unclear.

Studies by Rice el al. (1995) and Rice and Wexler (1996) revealed that the utterances of SLI children feature the same significant characteristics, i.e. the use of 01s alongside finite forms which displays knowledge of agreement and movement processes associated with finiteness. However unlike NL children SLI children appear to be ‘stuck’ in the 01 stage and the underlying nature of this deficit is unclear, e.g. there might be problems with tense or agreement or the use of non-finite forms might be a means of reducing processing load. Clearly the nature of the deficit has to be understood before the implicatim of the EOI theory for remediation can be understood.

This paper investigates whether 01 use in SLI children is affected by processing load Do the preverbal constituents in spontadeous utterauces influence whether an SLI child opts for the adult finite f m or the non-finite form or is occurrence random?

Using the Childes database (MacWhinney and Snow 1990) spontaueous language samples from 15 SLI/l8nguage-@aired children in the EOI stage were examined. Finite and non-finite utterances were categorised according to the structures which preceded the verbal constituents. Analyses were carried out to establish whether any patterns existed between these pre-verbal constituents and the use of non-finite forms.

Method

Subject selection Potential subjects were initially selected fiom the data set of SLVlanguage-

impaired children in the Childes database. These data were then examined and children selected who were very clearly at the EOI stage. Criteria for malcing this judgement were formulated and are summarid below.

424 Developmental speech and language processing

The only distinction at present between 01 and EOI comprises different points on a continuum of percentage 01 use in relation to age andor mean lcngth of utterance. The model of EOI as a clinical marker for SLI is not yet clear enough to allow us to label 01 use as part of an EOI stage simply because a child is SLI. It is duration of the stage significantly beyond the normal age raage that attracts the label. Wexler (1994) suggests 3 years as the age of emergence and Rice el ul. (1995) found that NL children of 4;07 years and over used non-finite clauses in only 5% of compulsory finite contexts. Therefore, for the purposes of selecting children’s data, criteria of no less than 30% use of non-finite matrix clauses in compulsory finite contexts and a lower age limit of 4 years (no upper age limit) were used to ensure a high level of conftdence that the data included in the main analyses were those of children who were indeed in the EOI stage.

Once selected by age, each child’s percentage 01 use in obligatory finite contexts was calculated. This required extraction of utterances where the target form was clearly an obligatory finite clause and then further extraction of those whose structure revealed their fite/nonn-finitc status (see utterance inclusion criteria). Provided a child’s data included 30 or more such utterances, this k a l set was used to calculate the percentage 01 use and if it were 30% or higher, the child was deemed EOI and the data included in the main analYSeS.

Utterance inclusion criteria The first stage in gaining the relevant data was an initial scree&g for utterances

which included a verb or were deemed to have required a verb in the target utterance. This latter judgment was made using immediate liagutstic context and the child’s actions as noted by the transcriber. Such judgements cannot always be made with full conftdence and depend partly on the amount of contextual detail provided in the transcription. In addition, establishing children’s target utterances is fiaught with theoretical issues as well as the subjectivity of individual interpretation. Consequently if the judgement ‘required a verb in the target utterance’ was uncertain, the utterance was not included.

The data thus extracted were then filtered Mer in order to calculate the proportion of non-finite to finite clauses. Owing to the weak agreement patterns of the English verb system only certain morphosyntactic forms reveal whether a child’s underlying form is finite or non-finite. So for inclusion in the data contributing to the EOI judgement, clause structure of utterances (or their target structure) had to be one of these types: 0 Lexical verb in a 3rd person srngular context 0 Auxiliary (be, have, do, and modals) or copular verb f m obligamy

Irregularpasttease 0 Regularpasttense

Inclusion of the relevant inflections or morphological forms in such utterances signifies finiteness. Their exclusion (and use of the infinitive verb form instead) signifies non-finiteness (unless due to accepurble ellipsis). Any utterances not fitting these syntactic criteria, stereotypicahon-productive utterances and those of uncertain classification were excluded. One exception to this were utkmuces in which the infinitive verb form was used and where the target, although uncutain, was clearly one or other of the above. Such utteaances were classified as non-finite.

Preverbal constituents analysis Fifteen children were deemed to be in the EOI stage. Their ages and percentage 01

use are shown in Table 1. The same utterances which were used for the EOI judgement were classified ~ c c o ~ d m g to their preverbal constituents. These data, (Hargrove et ul.

Developmental speech and language processing 425

1981, Bliss 1988, Conti-Ramsden and Dykins 1991, Conti-Fbnden el al. 1995, Conti- Ramsdea and Jones 1 W ) were then pooled, providing a total of 1808 utterances. Owmg to low incidence of some utterance types, some categories were collapsed provided parity existed in features such as word length and reference and case pr@es. Remaining categories with fewer than 10 utterances were omitted (e.g. determiner adjective noun). Percentage 01 use for each preverbal collstlhlcllt category was calculated for the pooled data (see Table 2) and for each child (see Table 3).

Table 1. Subjects

Child Age % O I U ~ 1 4;11 70.0 2 4;04 47.9 3 5;07 75.3 4 4;034;09 76.6 5 4;06 35.5 6 4;09 43.6 7 5;09 53.1 8 11;08 38.3 9 5;07 52.5 10 8;OO 31.0 11 4;11 76.7 12 6;04 41.5 13 6;09 41.7 14 4;034;08 42.7 15 6;OO-7;4 74.6

Table 2. Percentage 01 Use

46.6% 53.4% 120 87

58.0% 42.0% 125 57

68.7% 31.3%

71.9% 28.1% oordinate/subordinatclause 48 47

Results

As the total number of analysable utterances for each child varied widely, statistical analysis was not appropriate and therefore the percentages w e examined for pstterns withinthedata

In comparing the percentage 01 use in each category to the overall percentage 01 use it was noted that only noun and mrdizntdsubordinate clause categories echoed the overaU pattern to witbin 10%. Personal pronoun and no preverbal constituent categories both showed lower 01 use' than the overall pattern whereas the categories wh words, detexminer noUn/sdjective noun and demonstrative pronodherelthere as subject all showed a higher 01 use than the overall pattern.

The m e 01 use of individual children with a minimum of 10 uttexances in each of these categories was examined in relation to their own o v d 01 use to see whether it reflected the general pattern (see Table 3).

' Percentage 01 use is termed higherAower than overall use when a difference of 10% or greater existed.

426 Developmental speech and latguage processing

Noun and mrdinatdsubor-e clause utterances were too low in nearly all the children to allow any real patterns to be observed. Sufficient no preverbal constituent utterances were seen in six children. Four of these six showed less 0 1 use in this category than in their own overall pattern, mirroring the general trend, and one showed more 0 1 use than in his overall pattern. All fifieen children had ten or more utterances within the personal pronoun category. Seven showed less 01 use in these utterances than in their own individual 0 1 use as in the general trend. Two children showed more 01 use. In the category demonstrative pronoudherdthere as subject, six children had ten or more utterances. They all mirrored the general pattern, showing a higher rate of 0 1 use than in their own overall pattern. Determiner noudadjective noun and wh word categories each featured four children with ten or more utterances. In each category, two of the four reflected the general trend in featuring greater 0 1 use than overall use and one showed less 01 use than their overall paitem. The fourth in each category showed similar 01 use to their overall pattern.

Table 3. Children’s Percentage 01 Use in Preverbal Constituent Categories

Child None Dem.pron/ Personal Noun Wh Detor Subord.or Overall

1 17.6 91.4 58.5 65.0 89.0 82.4 53.8 70.0 2 13.0 87.8 20.8 50.7 35.8 35.0 58.8 47.9

4 66.7 88.9 72.2 * * 84.6 * 76.6 * * 35.3 * * * * 35.5 5 6 25.0 * 50.0 * * * * 43.6 7 * * 65.5 * * * * 53.1 8 * * 39.4 * * * * 38.3 9 * 69.2 32.1 * * * * 52.5 10 * * 39.4 * * * * 3 1.0 11 * * 66.7 * * * * 76.7 12 * * 58.8 * * * * 41.5 13 * * 41.2 * * * * 41.7 14 68.8 57.1 25.8 * * * * 42.7 15 * * 61.5 * 81.0 * * 74.6

*denotes categories featuring less than 10 utterances.

herdthere pronoun words adj noun coord clause

3 52.0 96.8 65.0 85.0 85.7 85.0 *= 75.3

Discussion

Several interpretations of these results can be made. Firstly, as each category does not share a similar distribution between finite and non-finite, there does appear to be an effect W e e n preverbal constituent and finiteness. The two notable trends, higher 01 use with determiner noddjective noun and wh words and lower 01 use with empty subjects and personal pronouns, may reflect two processes: processing load factors and linguistic factors respectively. Perhaps complexity, e.g. length in the case of two-part subjects (versus empty subjects and personal pronouns), and the movement processes involved in wh movement increase procesSing load and therefore favour non-finite forms. Empty subjects and pronouns are shorter than two-part subjects and may therefore favour finite forms. In addition, pronouns have a special status in relation to agreement. Even in

Developmental speech and language processing 427

languages where agreement is generally optional, it is usually obligatow with weak pronouns. The higher occurrence of finiteness (and thus agreement) with pronoun subjects may reflect this universal property. Although the demonstrative pronoun category seems to run contrary to ri processing load explanation, combining herdthere (which do not feature agreement) with the demonstrative pronouns (which do feature agreement) may have disguised a more revealing pattern of 01 use. A third possible factor is that finiteness may favour the subjects with which children are more familiar and use more frequently.

Clearly further research is required in this area. An experimental study looking at the preverbal and within verb phrase complexity of matrix clauses is in progress, as is further spontaneous language analysis based on the findings discussed here. The identification of SLI children's difficulties with verb morphology and auxiliary/copular omission as surface features of one underlying process has clear therapy implications in itself. Whether the process can be influenced in therapy by elicitation techniques which manipulate complexity levels elsewhere in the syntax has yet to be shown. Such methods are of course commonly used in assisting children to achieve general language production targets. However evidence that they may in some way be assistmg the child to use an option which has such a k-reaching effect on the success OT failure of so many surface structures would mean that the techniques were firmly grounded in linguistic theory.

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