BLOQUE DE CONSTITUCIONALIDAD

In Chapters 6, 7 and 8 of this thesis I have demonstrated that a range of phonological factors affects regular and irregular past tense inflection in both typically developing children and those with G-SLI. In this section I discuss the results of the study reported in the present chapter, which concern suffixation of the lid l allomorph in regulars and the impact of verb-end phonology on bare stem and over-regularisation errors in irregular

v e :! >s i <1 ih\>,n i: i ii , I, , , ill:. nl the studies in C hapters 6 and

whi I. /v. i*: «... , , .; .,v • t■ • i i p io so d ic co m p le xity on regular

111 • i in ( o m putation al G ram m atical

C om ple xity that ! p ro p o s e i i ; Stv ; . Waiting point for the discussion, I

s u m m a ris e the re su tts of the le ie vu m -u o ! u im. .> 8.10 1 present a sum m ary of the

results w ith re s p e c t to re y u la i u the basis of correct

p e rfo rm a n c e In red a ie the m giuups. and in blue are the results

that a ie id e n tic a l for both yiou|.

T a b le 8.10. S u m m a ry of le s u lk ✓ei i >.>

P h o n o lo g ic a l T a s k C o l K ill 11 G -S LI g ro u p s C o n trol g ro u p s ’

fa c to r p e rfo rm a n c e perform ance

P rosodic J u d g e m e n t VV-D > VC-D > VV-D = VC-D =

c o m p le xity VVC-D VVC-D

P m so d rc EliSrfalion VV-D > VC-D > VV-D = VC-D =

co m p le x ity VCC-D VCC-D

f u l l a H om oiph F lic ila tio n SS-D > VV-D > SS-D > VV-D >

t /d - id t /d - id

T h e re su lts lor the stud ! • rm n a ris e d in T a b le 8.11 and are

p re se n te d s lig h tly d iffe re n tly to ih £ r- • nil1 : : oi uii judgem en t task (C hapter 6),

c o m p a ris o n s a re m ade on If j todorrnance. For the elicitation task

(C hapter 8 ) , c o m p a ris o n s a n . . i >i 1 >nre stem and over-regularisation

errors A g a in , re s u lts that d iflts ■b e t'W - ■ ■ i ]i ■ in i.g h ifd in red, and results that are

identical fo r bo th g ro u p s are he

T a b le 8.11. S u m m a ry of result:s fot .

P h o n o lo g ic a l T a sk G -S LI g r o u p ’ s C ontrol g ro u p s ’

fa c to r p e rfo rm a n c e p erform ance

P ro so d ic Ju d g e m e n t V V P •• ; ■ VV-D = VC-D = VV-D = VC-D =

c o m p le x ity 1'1 VVC-D VVC-D

f u l l a lie n ii'irp h F lic iM tio n VV-D = VC-D > VV-D = VC-D >

(bare stem ) V ! •■/ , t/d - id t/d - id

E licitation VV-D > VC-D = VV-D > VC-D =

The data clearly show that the use of the

hd!

allomorph is problematic not only for those children with G-SLI, but also for their typically developing, language-matched controls aged 5;04-8;05. In Section 8.1.2 I hypothesised that one reason why

I id!

might be difficult to use is that children resist changing the metrical structure of words. It is impossible to distinguish between this hypothesis and the affix-checking hypothesis because the past tense allomorphs

Itl

and

Id!

are the very stem-final sounds that condition the selection of the

lid!

allomorph. However, the data collected here allow us to rule out one possibility - that a two-syllable inflected output is generally more difficult to produce than a one-syllable output, and that suffixation with

lidl

is disfavoured for this reason. A comparison of inflection rates between two-syllable verbs and one-syllable verbs ending in

Itl

or

Idl

reveals fewer bare stem errors for the SS-D compared to the

t/d-id

condition. That indicates that the lower inflection rate for the

t/d-id

condition is either due to the change in metrical structure being disfavoured or due to the segmental content of the stem making the verb appear already inflected. An interesting result is that there are more correct responses for the SS-D than for the W -D condition. One possible explanation for this finding is that all two-syllable verbs with strong-weak stress (i.e. the stimuli used in this study) are regular, and therefore a sw pattern is an unambiguous cue to morphology. Note that there are a handful of two-syllable irregular verbs, but the majority are prefixed and have final primary stress, e.g. begin, become, withhold, upset etc.

As regards irregular verbs, I agree with Stemberger and Middleton (2003) that, with cognitive science’s fixation on the differences between regular and irregular verbs, differences within irregulars have been largely ignored. (A notable exception is Bybee & Slobin, 1982). In this study I have shown that the phonological characteristics of irregulars do indeed affect morphological behaviour. As predicted, there are more bare stem responses for the

t/d-id

condition than for either the W -D or VC-D conditions, and verbs in the VV-D condition are over-regularised more frequently than those in the

t/d-id

or VC-D conditions.

Both G-SLI and control groups double mark irregulars, e.g. *fiewed, *tored,

*wonned, etc., albeit on only a few occasions. Presumably this reflects the fact that

irregular past tense forms are stored in the lexicon, and therefore available for suffixation. Children with G-SLI also double mark regular forms, e.g. *tieded, *cheweded, *roweded, but this type of error is not found in the typically developing children tested here. I tentatively interpret this result as providing a clue that regular past tense forms are stored

by children with G-SLI, meaning that they are available as stems for suffixation. Alternatively, the fact that responses of this type are not recorded in the elidtiation of W-D verbs in the task in Chapter 7 suggests that their presence here is due to priming effects from the t/d-id verbs that are also used here, e.g. needed and started. If this is the explanation, then it suggests that representations of regular past tense forms in the G-SLI group are not as secure as those of typically developing children, since the typically developing children resist priming.

When trying to understand the phonological pressures on the over-regularisation of irregular verbs we have to distinguish two separate pressures - what an ideal output should look like, and how difficult the change from input to output is. Ride already has the shape of an ideal output, whereas tear does not. This could explain why verbs such as

tear are over-regularised more frequently than verbs such as ride (e.g. Bybee & Slobin,

1982). A second reason why tear might be over-regularised more often than ride is that adding a Id! to a stem ending in a vowel ending is easier in some way than adding an extra syllable. In terms of syllabic structure, there is nothing more complex about *rided than there is about *teared. *Rided has two syllables, but it is still a trochaic foot, but no reason why that should be a problem. The difficulty is in telling which of these two pressures is operative - and indeed both may be.

It would have been informative to investigate more thoroughly the impact of metrical structure on regular inflection. One can imagine that differences in metrical structure could lead to differences in bare stem errors for three-syllable verbs of the form

drganised versus remdmbered. However, it would actually prove very difficult to do this,

which is why I omitted just such an investigation. The majority of English verbs consist of a single syllable. Two- or three-syllable verbs tend to have lower frequencies and later ages of acquisition, and it would be difficult to find enough stimuli that would be in the vocabulary of our youngest control children.

Now I discuss the effects of verb-end complexity, starting with regular verbs. For the judgement and the elicitation tasks, the results pattern the same way - complexity affects G-SLI children but not the typically developing children tested here. However, I predict that complexity effects would be present at a younger stage of development, because consonant clusters are acquired after singleton consonants: the study would need to look at younger children in order to confirm this. Although for the typically developing children tested here complexity no longer affects performance, use of lidl continues to be problematic.

What about the effect of complexity on irregular verbs? The results are the same for both the G-SLI and the typically developing groups. There is no effect of verb-end complexity on judgement, and I argued in Chapter 6 that this is because children don’t need a representation of verb-end complexity when judging whether a form is present or past - the vowel quality indicates which is which. Where it comes to producing bare forms and over-regularised forms though, verb-end complexity does have an effect. When the verb end would contain a cluster if suffixed, we see more bare stem forms and fewer over- regularisations.

Marchman et al. (1999) claim that an over-sensitivity to phonology interferes with efficient lexical processing and hence the organisation of general patterns across inflected items. In my view this seems a strange way of looking at the impact of phonology on past tense inflection. I fail to see the logic of why a heightened sensitivity to phonology should cause difficulties with morphology. Isn’t it just as likely that, given the cues that phonology provides to morphology, such a sensitivity should aid children with SLI in their acquisition of morphology, causing them to have better morphological skills than their language- matched peers? Nor can I see how this account would tie in with other explanations of SLI as being caused by poor auditory perception, and therefore poor phonology. Furthermore, it is hard to conceive that phonological problems alone can explain all the morphological errors that G-SLI children make. G-SLI children make bizarre morphological errors that are not made by any of the control children tested here. For example, here are some of QC’s mistakes from the elicitation task reported in this chapter. In each case the target is the past tense, but he produces a variety of alternative forms:-

• Future e.g. *will get

• Past with did e.g. *did weigh

• Progressive minus the auxiliary e.g. *tearing • Present progressive e.g. *am running • Past progressive e.g. *was throwing • Auxiliary with bare stem e.g. *am lead • Double marking on regulars e.g. *paided • Past participle e.g. * broken

• 3 person singular e.g. * blows

• Past tense marked on object noun e.g. *am marrying a dancered

In other words, QC makes ten different error types (in addition to over-regularisations of irregulars), which must surely indicate faulty morphosyntactic knowledge. There are two possibilities, of which he may be using one or other, or both: (1) QC is creating suffixed

forms by rule, but is unsure which particular suffix has past tense meaning and what the -

ed suffix should attach to, or (2) QC is selecting already suffixed forms from his lexicon.

Some of these types of errors have been acknowledged by previous studies on SLI but not discussed (e.g. van der Lely & Ullman, 2001), or discussed but left unaccounted for (e.g. Marchman et al., 1999). Nor are they discussed in any connectionist simulations of the past tense deficit in SLI or aphasia. Certainly these errors are problematic for accounts which claim that SLI children have a pattern of normal but delayed development, such as the Extended Optional Infinitive account (Rice, Wexler & Cleave, 1995). However, Bird, Lambon Ralph, Seidenberg, McClelland and Patterson (2003) report instances of adult non-fluent aphasic patients using -ing in place of the past tense suffix in elicitation tasks.

In conclusion, it appears that verb-end phonology really does affect past tense morphology in the G-SLI group. The next question of interest is whether phonological factors also affect other types of inflection, and derivational morphology. This is the issue at the heart of Part 3 of this thesis (Chapters 9 to 11). Before moving on, however, I use the next section to develop the CGC hypothesis.

8.4.3. The deficit in Computational Grammatical Complexity (CGC)

In document Eficiencia de los tribunales constitucionales locales (página 37-45)