Methods to investigate children’s perceptual knowledge

In order to take a closer look at children’s language competence, perception studies take advantage of children’s attention spans. Usually, infants show their interest in a speech signal by turning their head towards the sound source. When for example a caregiver enters the room out of the baby’s field of vision, the baby turns his or her head towards the adult upon hearing him or her talk. If babies are interested in the sound string, they keep looking at the source. The Head Turn Preference Procedure (HPP) is based on this observation. In this test method, young children between the age of six and twelve months are presented with auditory stimuli if they turn their head towards a flashing light mounted above a loudspeaker which is situated at the left or right side of the child. The sound sequence from the loudspeaker is stopped if the child looks away for more than 2s.¹ Looking times for different sound stimuli can be measured and compared. Studies including the HPP are used to demonstrate for example whether children perceive different intonation or sound patterns (e.g., Jusczyk et al., 1993).

The Switch Procedure (SP) is applied to examine whether children detect fine phonetic contrasts. Children are first habituated to a certain syllable that is presented repeatedly while they are looking at a checkerboard on a screen. As soon as children’s looking times towards the screen decline sharply, the habituation process is completed and the new syllable is presented. This new syllable usually differs only in one segment with an alternated manner or place of articulation. If children start to fixate the screen again, it can be deduced that they noticed the switch.² The procedure is mostly applied at a stage when children start to form phonetic categories (i.e. between 6 and 14 months of age).

1For more information on the experimental setup, please consult Houston (2005) or Jusczyk, Friederici, Wessels, Svenkerud and Jusczyk (1993).

2For more information on the experimental setup, please consult Stager and Werker (1997).

In the Preferential Looking Paradigm (PLP), children’s looking times are also measured but in this experimental setup, two objects are presented on a screen. One of them is labelled and children usually turn their head towards that specific object if the label is pronounced correctly. In case the label contains a small pronunciation error and children notice this error, they are confused and switch their gaze between the two objects.³ Studies applying the PLP have shown that children are able to detect small mispronunciations at the word onset and offset (e.g., White and Morgan, 2008). The designs of the perception studies outlined above are nearly identical in many laboratories in the world to allow for scientifically established comparisons between language-specific results.

The present chapter depicted the stages in language development for normal-developing monolingual children as well as bilingual children. It was pointed out that the developmental stages are invariant and proceed in a constant order for all children, regardless of the amount of languages children are exposed to. However, variation in rate of acquisition occurs across children and within bilingual children for their two languages. Moreover, three effects on the rate of vocabulary development were outlined. First, a higher socioeconomic status of the family of the child has a positive impact on the vocabulary development until approximately the age of four years. Second, high-frequency word are acquired earlier than low-frequency words but frequency effects diminish after the age of two. Finally, several studies investigating gender effects were able to show that the vocabulary inventory grew faster in girls compared to boys. The effect of gender decreases between the age of 20 to 24 months.

It was pointed out that both perception and production studies are necessary to shed light onto the process of language development in children. Subsequently, several methods to investigate children’s perception and production were introduced. This background information serves as the basis for the selection of the research methods of the two studies of this thesis. The following chapter provides results from previous research on the acquisition of complex rhythmic and prosodic structures. Evidence from previous studies will be taken as the basis for the research questions of the studies of this thesis.

3For more information on the experimental setup, please consult e.g., Swingley (2003).

The Acquisition of Phonological and Morphological Structures in Early Childhood

As mentioned in Chapter 4, children’s steps in their language development are very similar across languages. The phases in which children acquire certain aspects of their mother language follow the same order and children’s early productions devi-ate from the adult form in comparable systematics. Based on previous studies, the present chapter provides insights into the acquisition of different phenomena within the syllable and at the word-level. In general, most research findings are based on monolingual child speech. Where available, reference is also made to results obtained from bilingual children.

A general problem pointed out by Menyuk and Menn (1979: 52) is the fact that there is only a limited number of studies investigating the direct link between perception and production within one group of children. The studies that took both aspects into consideration obtained contradictory results with respect to the order of acquisition. In the 1950s and 1960s, the prevailing opinion was that perception pre-cedes production. McCarthy (1954: 520) formulated it in the following way: “Most writers agree that the child understands the language of others before he actually uses language himself.” A study on the relation between children’s production and comprehension abilities conducted by Fraser, Bellugi and Brown (1963) supports this

view. Their results demonstrate that three-year-old children perform better at point-ing at the correct picture of a scene named by the experimenter than describpoint-ing it themselves. In the 1970s, skepticism towards this assumption arose. Revised scores in a study by Fernald (1972: 611) suggest that children’s perception and production skills develop at the same rate. The children’s tasks were to select one picture out of a pair of contrasting pictures that matched the experimenter’s description of a scene and to describe a depicted scene. Overall, there was no significant difference between children’s perception and production scores. Clark, Hutcheson and Buren (1974: 49, 52) went as far as claiming that production is ahead of some parts of comprehension.

The authors argue that in order for the child to be able to follow an adult’s utter-ance, the child must have established a picture of the whole situation. By contrast, a child’s utterance is usually based on a context that is already obvious to the child.

Ingram (1974: 331f.) examined the above mentioned studies on the relation between the development of production and comprehension in greater detail. Based on these research findings in total, Ingram is convinced that there is a developmental gap between comprehension and production and that the former evolves earlier than the latter. Ingram points out that the definitions of comprehension and production should be clear: the view suggesting that comprehension precedes production does not imply that the whole process of comprehension is completed before the onset of production. The following subsections on previous perception studies precede the subsections on children’s production, in line with the view of Ingram (1974).

5.1 The acquisition of sound segments and sound strings

According to Best (1984: 99), babies are considered as prelinguistic until their first year of life. That means that babies’ early babbles are meaningless as they do not refer to objects or events. Moreover, babies do not yet have any language compre-hension skills. The prelinguistic phase does not imply that infants do not develop sensitivity to the sounds of their mother tongue or that they are not sensitive to certain aspects of language, such as rhythm and intonation. For such aspects, early

sensitivity has been demonstrated. The point is, however, that sounds, rhythm and intonation are not employed yet in a linguistic system.

The focus of the present section lies on the emergence of phonology at the begin-ning of babies’ linguistic phase. As opposed to the development of young children’s receptive abilities, their developmental steps in production can be traced easily. While the previous chapter concentrated on the methods to gain insight into children’s de-velopment of language competence, the present section is concerned with research findings from previous studies. When children start to produce their first meaningful sound strings, their utterances often contain deviations from the adult-form (cf. Sub-section 5.1.2). Yet, children’s perceptional knowledge of the adult-like pronunciation is already well established (cf. Subsection 5.1.1). The following two subsections pro-vide results from previous studies that demonstrate the disparity in phonological development in perception and production.