There is broad consensus in the literature that children need linguistic input in order to acquire a language successfully. All children who share their mother language go through the same sequence of stages in their language development. However, various factors may have an impact on the acquisition rate of an individual learner. Based on previous research findings, the following paragraphs examine three of these factors more closely: socioeconomic background, word frequency, and gender. The impact of these factors is readdressed in the design of the empirical studies of this thesis.
Socioeconomic status
In recent years, several studies were able to establish a link between the socioeconomic status (SES) of the family of the child and his or her language acquisition rate. Hoff (2003) conducted a study with two-year-old children who stem from families with different socioeconomic backgrounds to test the hypothesis that there is an impact of SES on productive vocabulary development. The author found that the children of parents with a higher SES show faster progress in their productive vocabularies.
Hoff’s explanation is that relatively uneducated mothers talk less frequently to their children and in shorter sentences compared to more educated mothers. Longer sen-tences consist of richer vocabulary, more complex grammatical structures and more varied syntactic frames.
Letts, Edwards, Sinka, Schaefer and Gibbons (2013) were able to establish simi-lar findings in a study with children between two and seven years of age. The results reveal that there is a correlation between the social class of the mother and the child’s performance in language production. This effect diminishes with increasing age. The authors observed that especially younger children from middle-class mothers are ex-posed to a richer vocabulary, longer sentences and a higher number of word roots as opposed to children from lower-class mothers.
The study by Black, Pepp´e and Gibbon (2008) tested children aged four to eleven years, but did not find a significant interaction between SES and the lexical development in children.
In conclusion, a higher SES of the family of the child has a positive effect on the active vocabulary development for children up to the age of four years approximately.
Word frequency
The second factor which may have an effect on the acquisition rate of children’s first words is frequency of occurrence. A logical assumption is that the more frequently a word occurs in parental utterances, the more likely it is to be acquired early by the child. In order to investigate this issue, Hart (1991) conducted a longitudinal study with children whose starting point in word production varied between the ages of eleven and seventeen months. The observation was stopped when children had reached the age of three years. In the beginning of the observation, the author finds a considerable correlation between the words uttered by the children and the linguis-tic input provided by the parents. However, this association decreases six months after the beginning of testing. By the age of two years, there is a significant re-duction in the strength of the correlation. Hart concludes that parental input has a demonstrable impact on early vocabulary acquisition. The decline in correlation suggests that children increasingly produce new words on the basis of aspects other than frequency, for example word associations and cognitive processing (Hart, 1991:
298f.).
Huttenlocher, Haight, Bryk, Seltzer and Lyons (1991) conducted a similar study on the influence of language input on the vocabulary growth in children. The results reveal that there is an interdependence between parental speech input and vocab-ulary development at 16 months of age. These results could not be confirmed for two-year-olds. This finding corresponds to the results obtained by Harris, Barrett, Jones and Brookes (1988: 87) in their study on word frequency effects on early lan-guage development.
Gender
It is often assumed that language is structured analogously in all native speakers of that language. However, according to Ullman, Miranda and Travers (2008: 291), var-ious factors have an impact on the neuro-cognitive function of each individual, one of
the most crucial ones being gender. The authors report several previous studies with adults which reveal that women tend to perform better than men in tasks involving language. In episodic memory tasks, women show an advantage with respect to the recall of lexical items and paragraph content. Likewise, females outperform males when it comes to the naming of synonyms or word associations (Ullman et al., 2008:
292). The question is: how early does the gender difference with regard to vocabulary growth surface?
Huttenlocher and colleagues (1991) conducted a study focusing on two aspects:
(i) the relation between parental speech input and the rate of children’s vocabulary growth as well as (ii) gender differences. The participants in the study were between 14 and 26 months old and they were observed at several points during that period of acquisition. The authors found a significant correlation between the amount of ex-posure to speech and the degree of early vocabulary growth. Moreover, the average vocabulary acceleration tended to proceed faster in girls than in boys, independently of the number of words uttered by the parent(s). However, at around the age of 20 to 24 months, the gender differences decreased (Huttenlocher et al., 1991: 242f.), which is consistent with findings by e.g., Maccoby (1966: 42f.). As girls do not re-ceive a higher amount of language input than boys, Huttenlocher et al. concluded that the gender differences found in early vocabulary growth “seem to reflect early capacity differences” with respect to first language acquisition (Huttenlocher et al., 1991: 245f.). An EEG-study conducted by Shafer, Yu and Datta (2011) found that English- as well as English-Spanish-speaking girls until the age of 14 months obtain better results in the detection of the [E]-[I]-vowel contrast than their male peers.
In conclusion, the process of LA1 is influenced by external factors. As demon-strated above, word frequency and the child’s gender have an effect on the early vocabulary development. Until the age of two, highly frequent words are acquired faster compared to low frequency words. In addition, girls are usually faster in the acquisition process. The socioeconomic background of the child correlates with the production rate until around the age of four. These factors are revisited in chapters 6 and 7, in the description of the experimental setups. It is left open for further dis-cussion which of the analyzed factors has the greatest impact. The following section
is devoted to the research methods that are applied to study children’s development of speech perception and production.