Early Language Development in Full-term and Premature infants

Paula Menyuk, Jacqueline W. Liebergott, Martin C. Schultz

• Publisher: Psychology Press
• Year: 2014
• ISBN:
  9781317779957
• Edition: 1
• Topic: Personal Development
• Subtopic: Writing & Presentation Skills

Designed to provide practical information to those who are concerned with the development of young children, this book has three goals. First, the authors offer details about patterns of language development over the first three years of life. Although intensive studies have been carried out by examining from one to 20 children in the age range of zero to three years, there has been no longitudinal study of a sample as large as this--53 children--nor have as many measures of language development been obtained from the same children. Examining language development from a broad perspective in this size population allows us to see what generalizations can be made about patterns of language development. This volume's second goal is to examine the impact of such factors as biology, cognition, and communication input--and the interaction of these factors--which traditionally have been held to play an important role in the course of language development. The comparative influence of each--and the interaction of all three--were examined statistically using children's scores on standard language tests at age three. The volume's third goal is to provide information to beginning investigators, early childhood educators, and clinicians that can help them in their practice. This includes information about what appear to be good early predictors of language development at three years; language assessment procedures that can be used with children below age three, how these procedures can be used, what they tell us about the language development of young children; and what warning signs should probably be attended to, and which can most likely be ignored. In addition, suggestions are made about what patterns of communicative interaction during the different periods of development seem to be most successful in terms of language development outcomes at three years, and what overall indications the study offers regarding appropriate intervention.

CHAPTER 1

The Study

Study of language development has been the focus of attention of a number of professions concerned with early childhood. Because language development plays a crucial role in social and cognitive development it has attracted the attention of educators and clinicians. Social and cognitive development, in turn, play a role in language development. In addition, the effect of biological state and maturation on language development has been a focus of attention. Researchers have studied premature as compared to full-term infants in hopes of determining the effects of biological state on development. Many studies have explored speech and language mastery in both full-term and premature infants as a way of examining whether or not there are early and late differences that can be found in this development due to prematurity per se or to the complicating medical or social factors that accompany prematurity. As stated, language development has been a focus of attention because of the important role it plays in social and academic development, although other aspects of development can be affected by prematurity and accompanying factors. (For further information on recent studies of the effect of prematurity on a number of aspects of development, outside of language development, during the early years of life, readers can look at Rosenblith, 1992.)

The questions of the comparative effect of social, cognitive, and biological factors and their interaction on language development has been examined in many studies. The answer to these questions are of theoretical and applied interest. The theoretical interest is that of explanation of this important development. The applied interest is to determine what may be important early deviations from normal patterns so that intervention may be planned. The study reported on in this volume was undertaken also to examine these theoretical and applied questions. The primary study took place from 1982 to 1985. Although a great deal has been learned from many studies before and after the study, the questions have still not been thoroughly answered. The results of this study, we believe, contribute to the answers.

In this chapter we summarize some of the results of studies that have examined the question of the effect of prematurity and the factors that accompany the premature state on language development, and indicate why we think the questions still remain unanswered. We then describe how we carried out our study: who the paticipants in the study were (the infants and their families), how we got them to participate in the study, and the methodology we used to collect and code data on the children’s language development. In subsequent chapters we discuss how we measured the children’s cognitive and linguistic development, and what we found out about their cognitive and linguistic development over the first 3 years of their lives. In the final chapter we present a summary and what we think the implications of these findings are. As an epilogue, we present our findings on a follow-up study of some of the children. Finally, we indicate what we think are the most promising questions that remain to be asked.

CONTRASTING LANGUAGE DEVELOPMENT IN FULL-TERM AND PREMATURE INFANTS

A large number of studies have focused on the question of the effect of prematurity on language development alone. Both older and recent studies of the language development of premature infants have found that they were comparatively delayed in the language they understood and the language they produced. These were the findings in a study carried out in the 1960s (DeHirsch, Jansky, & Langford, 1964), and in studies in the 1980s (Bailey & Wolery, 1989; Field, Dempsey, & Shumar, 1981; Siegel, 1982) and even in 1990s (McCormick & Schiefelbusch, 1990). Thus, over a period of almost 30 years, researchers have found that prematurity negatively affects language development, and for the most part, it delays it.

Although all of the studies just mentioned indicate a negative effect of prematurity on language development, which apparently places great importance on the effect of biological factors on this development, other studies indicate no such effect. Some studies comparing the language develoment of premature and full-term infants have found that early differences disappear at 2 to 3 years of age (Greenberg & Crnic, 1988; Ungerer & Sigman, 1983). A quite sizeable study reported (Aram, Hack, Hawkins, Weissman, & Borawski-Clark, 1991) concludes that specific language impairment (SLI), as defined and measured by certain standard tests, is not more frequent among the low birthweight children (infants weighing 1,500 grams or less at birth) than full-term children, at age 8. The children in both the very low birthweight (VLBW) and full weight populations were randomly selected from a community. There were more than 200 children in the low birthweight group and more than 300 children in the control group. Aram et al. (1991) also reviewed some 20 other studies that had examined this question and further concluded that the studies overall present a less than convincing argument that low birthweight is causally related to disordered speech and language. However, although the presence of a language disorder could not be attributed to low birthweight, there were significant differences between the low birthweight children and their controls on a number of measures of language development and the WISC-R, a standard measure of intelligence. Thus, one could conclude that, although language disorder was not related to birthweight, linguistic and cognitive delay might be.

Recent studies have asked whether or not prematurity affects other aspects of language development such as reading and writing. If such an effect is found it implies that early delays in oral language development, which may or may not disappear at 2 to 3 years of age, might affect later academic performance. Again the findings have been mixed. Some studies have found differences in the reading scores of prematurely born children, whereas others have found no such differences (Barsky & Siegel, 1992). In a study (Menyuk et al., 1991) that included some of the children who were infants in this study, it was found that some of the children who were born prematurely did have subtle oral language difficulties that were not evident when they spoke and, also, that they were not only significantly different from their age peers on a test of early reading development, but could be classified as at risk for reading. The emphasis is on the word some. Of the 27 premature infants who participated in the study, 4 performed as poorly as children diagnosed as having an SLI on standard tests of oral language development at 5 years old, 9 did as poorly as SLI children on an experimental oral language processing battery, and all of these 9 were identified as being at risk for reading failure at age 8. These latter findings are discussed at length in the final chapter of this book.

As can be seen, different studies have obtained widely different answers to the question. The reasons for the differences in findings are multiple. First, there is a wide diversity in the biological state of premature infants, regardless of their weight, although these two aspects of prematurity are related. Such biological risk factors as fetal distress, infection or sepsis, respiratory distress syndrome (RDS), metabolic problems and intraventricular hemorrhaging (IVH) may accompany low birthweight. The incidence of biological insult is greater, the smaller the infant. Such factors appear to play an important role in language development outcomes for premature infants. Another consideration is that infants who are premature and their full weight controls are born into families that vary widely in terms of socioeconomic status (SES) and cultural background, although, again, there is a trend. Premature births are more prevalent among poor women due to differences in nutrition and health-care delivery. Obviously, such socioeconomic and sociocultural differences can affect children’s performance on standard measures of language development. Biological factors associated with prematurity and social factors, in interaction with each other, might differentially affect language development.

Another complexity leading to differences in findings of studies might be that the prematurity of the infant affects mother-child interaction, and does so in differing ways depending on the personalities of an individual dyad (mother-infant pair) as well as the factors just cited. Some mothers perceive their premature children as being handicapped, and this can lead to differences in mother-child interaction (Brown & Bakeman, 1980; Sameroff & Chandler, 1975). Some mothers of premature children have been found to try harder. In one study of the first year of life of premature children, it was found that their mothers were more active and offered more stimulation than mothers of full-term infants, but that the infants themselves were less responsive as well as less competent than their full-term age peers (Crnic, Ragozin, Greenberg, Robinson, & Basham, 1983). This lack of responsiveness might have been the result of overstimulation. Clearly, studies finding differences when examining the effect of prematurity on language development versus the findings of no differences might be due to individual mother-child communicative interaction factors as well as to the biological and social factors discussed previously.

Differences in the measures of language development used in different studies might be one last factor to explain these variable findings. That is, which aspects of language were being measured, how they are measured, and what ages they were being measured at. In the Aram et al. (1991) study reported previously, a number of studies are briefly reviewed. In 15 studies listed, no two are alike in the measures used. In some, assessment of language takes place at one point and in others over a period of time, and at different ages from 9 months to 9 years. Measured IQ, vocabulary, articulation, or sentence comprehension and production (to mention a few developmental aspects) are different outcome measures reported on in different studies.

To summarize, there is a significant interest in explanations of language development and in detailing positive and negative influences on its rate and course. Many researchers have chosen to contrast development in premature and full-term children because prematurity may be expressed through differences in biological integrity, in cognitive maturity, and in caregiver-infant interaction. That is, the accompaniments of prematurity can be viewed as challenges to normal development so that a study population including premature as well as full-term children provides examples of various normal but differing paths as well as the course or courses of troubled children. Through careful documentation of the biological and environmental factors, plus when and how language learning deviates from the normal course, researchers have hoped to sort out the individual influences, their interactions, and their relative potencies.

The review of research findings provides some sense of how each of several influences impacts development but most studies followed too few children for too short a period, and the measures that were used varied by study. Therefore, the results of comparative research with premature and full-term infants have not led to assured or useful answers to the questions about comparative effects of biological, social, and cognitive influences on language development and their possible interaction.

There seemed to be a clear need for a study that would redress as many of these inadequacies as could reasonably be taken into consideration with a limited set of resources. Although many of the questions were straightforward, it could not be expected that the answers would be simple. The necessities were to observe developmental speech and language behaviors in a variety of children of differing backgrounds, under conditions that were as minimally artificial as could be managed. Those data would then have to be coupled with information on the biological integrity of the child, the child’s cognitive abilities, and important characteristics of the child’s environment, notably the infants’ interactions with their primary caregivers. All measures had to be acquired under stringent conditions of quality control, without having the need for rigor impact on the in-home behaviors of child or caregiver.

GENERAL CHARACTERISTICS OF THE STUDY

The specific measures that were scheduled and taken are discussed in a later section, but first the overall plan. The research was designed to obtain high quality recordings and observations of each child’s vocal behaviors and language growth, and of the associated, simultaneous environmental influences, from routine and periodic home visits. The goal was to collect samples of the child’s language emergence, and caregiver–child interaction, as well as what the child had not yet mastered.

Although it was desirable to observe each child continually from birth to 3 years of age (when standard tests can be used to assess and predict language development), the available funding was insufficient to support the total period required to recruit families into the study, watch 3 years of development, and then have time to evaluate the data. As an alternative, half the children were recruited into the study at birth and followed through 30 months of age, the other half were recruited into the study beginning at 9 months of age and exited after their 36-month evaluation. By synthesizing the trends of the findings, we expected to obtain a coherent view of the course of the first 3 years. The younger and older groups were equal in size and there were equal numbers of premature and full-term children in each.

Home visits were scheduled periodically and so as to accomodate the rhythms of both primary caregiver (mother mostly) and infant. Each family was linked with a specific member of the study group. That person was the regular and expected visitor and she established a close personal relationship with mother and infant and, often, with other family members as well. Family members were made full partners in the ongoing study to minimize the practice of any withholding behaviors from any party.

The full-term children in the study were recruited because they were born in a university medical school teaching hospital. This introduced some subtle selection criteria (unconscious on our part). Their families resided in or near a large metropolitan center and mothers chose obstetricians who delivered in a teaching hospital of a university medical school. Not so for the premature babies. Many of them were sent from various parts of the state to the medical school teaching hospital after birth because of prematurity and required special care. These babies were unselected by us, except for having been born very early and were not subject to the same sampling bias.

HOW THE STUDY WAS CARRIED OUT

To find out what the development of language looks like over the first 3 years of life, we chose to visit the infants in their homes. We felt that only by observing the children as they interacted and conversed spontaneously with their caregivers and their siblings would we be able to describe their language as it emerged. Recording the children in their homes also allowed us to observe, measure, and describe the natural interactions that might influence the children’s patterns of language development. We originally scheduled visits with each family a minimum of 23 times and a maximum of 28 times over a 2 1/2-year period but actually the children were seen more frequently than this. We often attended birthday parties and other family events. Also, on occasion the recordings were terrible or we missed recording all together because the tape recorders were broken or had weak batteries, or the child refused to talk very much or play some games with us. In cases such as this we went back to visit.

An average visit lasted 2 hours. Most often, one of the hours was spent with the caregiver (most frequently the mother) and child while they did what infants and their caregivers do during the day. The activities they engaged in varied depending on the time of day and the individual dyad. We did not ask the mothers to do anything special and we tried to schedule the visit at a convenient time for the family. Some visits involved our playing with and testing the children. These tests were experimenter-designed measures of speech sound discrimination and comprehension of multiword phrases and sentences. These are described in detail in chapter 2. When the children were 2 1/2 to 3 years of age they were brought to a speech clinic at a metropolitan hospital for a full diagnostic battery of standardized tests. These tests were administered by a certified speech and language pathologist.

Who the Children Were

In this section of the chapter we describe how we found the children in the study, what criteria we used to admit them, and what their birth conditions were. Some background information on their families will be given.

Locating the Children. We began the study by entering 56 different children and their families, 28 premature and 28 full-term babies. The number of babies was determined by two factors. First, we needed to have a large enough number from which to make meaningful generalizations about patterns of language development. Because many previous intensive studies of language development had had as few as 3 childr...