Children's acquisition of past tense morphology: an experiment

Transcription

1 Children's acquisition of past tense morphology: an experiment Hrafnhildur Ragnarsdóttir University College of Education, Reykjavík Hanne Gram Simonsen University of Oslo 1. Introduction How do children acquire the past tense of verbs? By rote or by rule? Maybe both? What kind of rules? Is there developmental change over time? These are questions one would like to answer for all languages, including the Scandinavian ones, which we are focussing on. We want to see how acquisition takes place for both weak (regular) and strong (irregular) verbs. But in fact both weak and strong verbs may be more or less irregular - for example, there are degrees of regularity also between the strong verb classes. We expect those differences to play a role in the acquisition pattern, and to show in the errors children make in their use of past tense forms. Most of what we know about children s acquisition of past tense morphology is based on research on English-speaking children (Marcus, Pinker at al, 1992). However, it is not certain that children learning other and morphologically more complex languages would give the same results. The Scandinavian languages seem an excellent testing ground for checking the cross-linguistic validity of the results found for English, each providing specific, slightly different cues to the children. We propose to test the acquisition of the past tense of cognate verbs in at least two of these closely related languages - starting with Icelandic and Norwegian, (and hereby inviting somebody to continue with Swedish, "Finnish Swedish" and Danish). 105

2 The Norwegian dialect used in the experiment is the Oslo dialect - a variant close to spoken East Norwegian "bokmaal". 2. The experiment We will conduct a set of parallel experiments in Icelandic and Norwegian, elicitating past tense forms of cognate verbs in the two languages. We will test 3 groups of children at years, with approximately 30 children in each age group. Each child is tested on approximately 60 verbs - 30 weak and 30 strong ones. (The distinction between weak and strong verbs is based on whether or not they have a syllabic suffix in the past tense - weak verbs have such a suffix, strong verbs do not.) 2.1 Elicitation task The elicitation task follows the pattern illustrated in Bybee & Slobin (1982): The child is shown a picture of someone performing an action. The experimenter says: "This is a boy who knows how to. He is ing. He did the same thing yesterday. What did he do yesterday?" And the child fills in (presumably with the past tense form of the verb): "He. " Let s say that we have a picture showing a boy drinking,.e.g. a glass of milk. In Norwegian, the experimenter will say: E.: "Dette er en gutt som er god til å/glad i å/holder på å drikke. Han gjorde det samme igår. Hva gjorde han da?" C.: "Han." 106

3 Here the child may fill in, e.g. drakk, or drikket, or drukk, - to show some of the forms elicited in a pilot experiment of this task in Norwegian. Note that here the verb is presented in the infinitive form by the experimenter. In fact, the choice of infinitive versus present tense in the elicitation task may be of importance in Norwegian: the single most salient marker of a strong verb in Norwegian is that it has a tone shift from Accent2 to Accent1 in the present tense. Generally, all (disyllabic) infinitives have Accent2, and all weak verbs have Accent2 also in the present tense (and in the past). But strong verbs change to Accent1 in the present tense: WEAK STRONG present past present past TIKKE 2 tikker 2 tikket DRIKKE 1 drikker 1 drakk KLIPPE 2 klipper 2 klippet SLIPPE 1 slipper 1 slapp TITTE 2 titter 2 tittet SITTE 1 sitter 1 satt LÆRE 2 lærer 2 lærte SKJÆRE 1 skjærer 1 skar GYNGE 2 gynger 2 gynget SYNGE 1 synger 1 sang All strong verbs in Norwegian have Accent1 in the present tense (plus those few verbs that were once strong, but are now regularised, like LESE ( 1 leser ~ 2 leste), DREPE ( 1 dreper ~ 2 drepte). This implies that if the children hear the verbs in the present tense form, it is a strong cue as to whether the verb has a strong or weak past tense inflection. To control for this, half of the Norwegian children will be given the infinitive as a cue: "en gutt som er god til å ", while the other half will be given the present tense as a cue: "en gutt som r". 107

4 3. Factors influencing acquisition We expect both frequency factors and factors related to the phonological properties of the verbs to be important for acquisition. Thus, the following are the main factors we will manipulate and try to evaluate in the experiment: Type frequency Token frequency Phonological coherence Phonological distance 3.1 Type frequency How many verbs belong to each inflectional class; i.e., how many verbs have the same phonological patterning, as defined by the way the past tense is formed? A class is defined as High Type Frequency (HiTyFr) if it has more than 30 members - as Low Type Frequency (LoTyFr) if it has less than 5 members. We will compare the children s performance on verbs from two HiTyFr classes (SV1 and SV2) and one group of LoTyFr verbs (SV3) among the strong verbs, and also compare with verbs from the two weak classes, where one (WV1) has a higher TyFr than the other (WV2). Token frequency will be kept as constant as possible. Predictions: a) HiTyFr verbs acquired before LoTyFr verbs: SV1/SV2>SV3; WV1>WV2; W>S b) HiTyFr verbs may form bases for (over)generalisations: (WV1, WV2, SV1, SV2) c) HiTyFr verbs are less likely to be regularised than LoTyFr verbs: (fewer overgeneralisation errors in SV1 and SV2 than in SV3, and fewer in WV1 than in WV2.) 108

5 3.2 Token frequency How frequent is the single verb in the input language? This is a measure of the frequency of use of each lexeme. To estimate this, we will use different, available sources: frequency dictionaries; frequency counts in available databases for adult spoken language; frequency counts in our own databases for both adult and child language. As a tentative criterion, a verb counts as High Token Frequency (HiToFr) if it has ten times as many occurrences as a Low Token Frequency (LoToFr) verb. We will compare HiToFr verbs to LoToFr verbs within the same class, and across HiTyFr classes. Predictions: a) HiToFr verbs >LoToFr verbs b) HiToFr verbs more resistant to overgeneralisations than LoToFr verbs. 3.3 Phonological coherence (of each verb class) This is a measure of how phonologically similar the members of each inflectional class are to each other - and at the same time to what extent they differ phonologically from members of other inflectional classes. The basis for comparison is restricted to the rime of the infinitive base syllable, i.e., the infinitive base vowel plus following consonant(s). The point is to see how predictive the phonological properties of the infinitive in each class is of the past tense form. A class has high phonological coherence (Hi P C) if none or few members of other classes share the phonological characteristics of the infinitive of this class. We will compare HiTyFr verb-classes differing in P C within each language. 109

6 Predictions: a) Hi P C > Lo P C b) Hi P C more resistant to overgeneralisation than Lo P C 3.4 Phonological distance (for each verb) While phonological coherence was a measure concerning the verb classes, the phonological distance is defined as the degree of phonological similarity between the infinitive base and the past form of each verb. The more similar these two forms are in each verb, the smaller the phonological distance for this verb. This implies that verbs with suppletivistic forms have the greatest phonological distance, verbs with both vowel and consonant change have greater phonological distance than those with only vowel change, and verbs with no change between infinitive and past tense have no phonological distance. The general prediction from this measure will be that the smaller the phonological distance of a verb, the easier the acquisition of the past tense will be. However - predictions may differ for Icelandic and Norwegian here: Icelandic children are used to vowel changes all through their paradigms, i.e., they are generally used to a higher level of phonological distance, so to speak. Norwegian children are not - for them, vowel change is restricted to irregular inflection, and mostly verbal inflection. 3.5 Other cross-linguistic predictions a) Icelandic children will have more difficulties in learning the past tense formation than Norwegian children, because of the generally more complex morphology in Icelandic, also outside the patterns we are testing. 110

7 b) Since vowel shift in Icelandic is used across the board for all sorts of morphological markings, Icelandic children may have to rely more on consonants to form class predictions. (In Norwegian, vowel shift in the past tense is highly indicative to single it out as a strong verb, each vowel indicating which subclass it belongs to.) References Bybee, J.L. and Slobin, D.I Rules and schemes in the development and use of the English past tense, Language 58: Marcus, G.F., Pinker, S. et al Overregularization in language acquisition. Monographs of the Society for Research in Child Development Vol 57, No