Early Language Acquisition and the Prosody-Morphology Interface : A Perception and Production Study with German and German-Italian Children

In first language acquisition, prosodic structures play a role both in the development of speech perception and production. Previous studies show that babies whose mother language is trochaic prefer this rhythmic pattern compared to other patterns (Jusczyk, 1999; Jusczyk et al., 1993, 1999). Moreover, children’s first words follow the rhythmic pattern of the mother language (Demuth, 1995), or they are adapted to fit this pattern by means of weak syllable omissions (Gerken, 1994a, 1994b, 1996; among others). So far, only a few longitudinal studies exist on the prosodically conditioned realization of weak syllables and morphemes in monolingual and bilingual child speech with a direct link to children’s perception of these utterances.The present thesis aims at filling this gap by presenting results from a production study with monolingual German and bilingual German-Italian children along with a perception study with German children. These two languages were chosen because they possess different rhythmic and grammatical structures. First, in contrast to German, Italian has a broader prosodic spectrum. Second, the functional elements in German carry more grammatical information compared to Italian. Finally, article use in Italian is higher than in German. These differences form an interesting baseline to draw a comparison to previous studies on English. English has a similar prosodic structure to German but compared to Italian, English functional elements carry less grammatical information. By investigating three different types of weak syllables, we aim to disentangle the contribution of prosodic biases and the contribution of grammatical load on the acquisition of German weak syllables.Chapter 2 presents the Theory of Metrical Phonology on which the two studies of the present thesis are based. This theory assumes that rhythmic structures are related to a hierarchical order of prosodic units while disregarding the morphological and syntactic structure. It is demonstrated how this theory is applied to match German and Italian phrases. Moreover, the similarities and differences regarding the prosodic structures of German and Italian are exemplified. Both the German and the Italian syllable may consist of an onset, a nucleus and a coda but only the nucleus is obligatory. In contrast to Italian, German allows a greater combination of consonants and consonant clusters are more frequent in German. Both German and Italian are trochaic languages. Italian belongs to the group of syllable-timed languages whereas German is described as stress-timed. The difference that plays a role for the present thesis is that in syllable-timed languages, full vowels in unstressed syllables may not be reduced.Chapter 3 addresses morphological aspects of German and Italian verbs as well as articles. The two languages have in common that verbs consist of a stem and an ending (with the exception of auxiliaries) and that verbs agree in person and number with the subject of the sentence. In addition, verb endings in German and Italian may carry information on time and mood. Italian has many more verbal exponents than German and some of them attract main stress. In German, verbal endings never receive main stress. Solely the use of certain affixes depends on the stress pattern of the stem. For example, the past participle prefix ge- is only used if the following syllable is stressed. In the dialect of Swabian, the prefix ge- may be reduced to [k] if the following verb stem does not begin with a plosive. Both German and Italian use definite articles but in Italian, definite articles occur in more contexts and thus more frequently compared to German. By contrast, definite articles in German carry more morphological information compared to definite articles in Italian. In German, definite articles express information on four cases, three genders and two numbers whereas in Italian, they express information on two genders and two numbers. In Italian, there are several article forms for feminine and masculine nouns. The choice of the definite article form within the two gender categories is phonologically conditioned. In German, the choice of the definite article form is grammatically conditioned.The steps in monolingual and bilingual first language acquisition are illustrated in Chapter 4, Section 1 and 2, respectively. Across languages, language development proceeds very similarly and even bilingual language acquisition proceeds in the same steps as for monolinguals (De Houwer, 2009: 5). According to the nativist approach (e.g., Chomsky, 1957; Pinker, 1984; and others), first language acquisition is initiated by a linguistic device that children have from birth on. This linguistic device helps babies to set the parameters of the Universal Grammar correctly according to the language input he or she receives. Regarding the vocabulary size, bilingual children may be delayed by three to six months compared to their monolingual peers (McLaughlin, 1978: 74, 91f.). This finding is ascribed to the greater mental workload that is required when learning two languages compared to one. Section 4.3 presents a couple of other factors that may have an impact on the rate of language acquisition: socioeconomic status, word frequency or gender of the child. For children up to age four, preceding studies found that a higher socioeconomic status has a positive effect on vocabulary size (Hoff, 2003; Letts et al., 2013). Children up to age two are more likely to acquire words with a higher frequency compared to words that do not occur as often in child-directed speech (Harris et al., 1988; Hart, 1991; Huttenlocher et al., 1991). Girls until the age of two have a larger vocabulary compared to boys of the same age (Huttenlocher et al., 1991). These three factors play a role in the experimental design of the empirical part of this thesis. The final section of Chapter 4 presents the research methods used in experiments on speech perception and production in young children. Based on this background, the ideal methods to address the research questions mentioned above are selected (see the description of the design of the studies).Chapter 5 outlines the findings by previous perception and production studies. Rhythmic structures are acquired very early which surfaces in babies’ ability to distinguish between two languages with different rhythmic patterns (e.g., Nazzi, Bertoncini and Mehler, 1998). Moreover, previous perception studies found that babies have a very detailed representation of words in their mental lexicon because babies are able to detect slight mispronunciations in the label of a familiar object (e.g., Bailey and Plunkett, 2002; Swingley and Aslin, 2000, 2002; White and Morgan, 2008). Children’s deviations in their word and sentence productions is thus a strategy to simplify complex structures. Gerken (1994b, 1996) for example examined the production of English weak syllables within phrases that exhibit two different rhythmic patterns. The author found that weak syllables are more likely to be realized if they form part of a trochaic foot compared to lapses consisting of two or three adjacent weak syllables.The production study with German and German-Italian kindergarten children is presented in Chapter 6. The main research question is whether the realization of definite articles, noun-initial weak syllables and prefixes also depends on prosody in German child speech. Further aspects such as grammatical load of the type of weak syllable and influences from another language in bilingual children are investigated as well. One group of German children between the age of 1;8 and 3;10 as well as one group of German-Italian children between the age of 2;6 and 5;6 were recorded using elicited imitation. The results demonstrate that the monolingual children tend to omit weak syllables less often and until a younger age compared to the bilingual children. Considering the type of weak syllable, the children in the two language groups omit the word-initial weak syllable Ge- more often than the prefix ge-. This result speaks in favor of a preference for weak syllables that carry morphological information.Chapter 7 is devoted to the perception study with young German children. The main research questions are whether 18-, 27- and 36-month-olds detect mispronunciations that were found in the children’s speech data in the production study and whether different types of mispronunciations are rejected as a label for a certain object to different degrees in the three age groups. The results confirm the first research question. They also show that the acceptance of a mispronounced label depends on the age of the child. The children in the youngest age group accept mispronunciations that simplify complex prosodic structures as long as the trochaic pattern is preserved. For the children in the oldest age group it is important that all speech sounds are maintained and a change to a pattern that contains a word-initial weak syllable induced by a weak vowel insertion is accepted. The children in the middle age group show an intermediate behavior.The final chapter provides a general discussion in which the two studies are reconsidered critically and related to findings from previous studies. Our production study revealed that both German and German-Italian children omit or substitute speech sounds to avoid complex clusters, weak word-initial syllables or difficult sounds such as the voiceless palato-alveolar fricative (see also Hoff, 2001). The findings of our production study confirm findings from previous production studies on the influence of rhythmic patterns on children’s realizations of weak syllables. Our perception study showed that children in general detect the mispronunciations based on our production study. We conclude that children’s deviations from the adult form may be based on a preference for simplex structures rather than on imprecise lexical specifications. Finally, it is illustrated in what way the present studies may serve as the basis for future research in that field.publishe