Behavioral genetics: concepts for research and practice in language development and disorders

Pro-nominal reference skills of second and fourth grade children with language impairment

Pro-nominal referencing was evaluated in a sample of 569 children comprising four diagnostic subgroups: typical language (TL), specific language impairment (SLI), nonspecific language impairment (NLI), and typical language with low nonverbal IQ (LNIQ). Participants generated oral narratives in second grade and again in fourth grade. The narratives of the females in the TL group included a significantly higher rate of pro-nominal references than the narratives of both the males in the TL group and the females in the NLI group. A higher percentage of complete pro-nominal references was found in the TL group compared to the SLI group. These findings suggest that pro-nominal referencing measures are not sensitive enough to differentiate school-aged children with typical language development from those with language impairment.

LEARNING OUTCOMES

The reader will: (1) become familiar with narrative language measures and (2) learn how groups of children with varying language and cognitive profiles perform on measures of referential cohesion.

Disorders of speech development: diagnostic and treatment aspects

Language acquisition is a complex process relying on the well-tuned interaction of a variety of factors. Its genetic base is still little explored, but perhaps plays the most important role during the early periods of this process. In addition, neurological, cognitive and emotional abilities of the child as well as verbal stimulation from the environment are crucial. Language development disorders manifest themselves as late onset, slow progression or as erroneous course of the language development. Because of the multitude of factors involved, their aetiology is frequently difficult to determine. Diagnosis of such disorders commonly requires the cooperation of several professionals, like paediatricians, otolaryngologists, psychologists, and speech pathologists. The "late bloomer" hypothesis suggests, that up to 50% of children presenting with language problems in early years, make up for them without intervention up to age four years. Nevertheless, treatment for a language problem, as soon as it appears, is generally recommended in order to minimize adverse effects on succeeding developmental steps.

Oral and written story composition skills of children with language impairment

In this study 538 children composed 1 oral and 1 written fictional story in both 2nd and 4th grades. Each child represented 1 of 4 diagnostic groups: typical language (TL), specific language impairment (SLI), nonspecific language impairment (NLI), or low nonverbal IQ (LNIQ). The stories of the TL group had more different words, more grammatical complexity, fewer errors, and more overall quality than either language-impaired group at either grade. Stories of the SLI and LNIQ groups were consistently stronger than were those of the NLI group. Kindergarten children with language impairment (LI) whose standardized test performance suggested normalization by 2nd grade also appeared to have recovered in storytelling abilities at that point. By 4th grade, however, these children's stories were less like the children with TL and more like those of children with persistent LI than they had been in 2nd grade. Oral stories were better than written stories in both grades, although the greatest gains from 2nd to 4th grade were generally made on written stories. Girls told stronger stories than did boys at both grades, regardless of group placement. It is concluded that story composition tasks are educationally relevant and should play a significant role in the evaluation of children with developmental LI.

Atypical brain development: a conceptual framework for understanding developmental learning disabilities

This article presents ideas that are, in part, a response to the ambiguity in the neurological research on learning disorders, the growing awareness that developmental disabilities are typically nonspecific and heterogeneous, and the growing scientific literature showing that comorbidity of symptoms and syndromes is the rule rather than the exception. This article proposes the term atypical brain development (ABD) as a unifying concept to assist researchers and educators trying to come to terms with these dilemmas. ABD is meant to serve as an integrative concept of etiology, the expression of which is variable within and across individuals. ABD does not itself represent a specific disorder or disease. It is a term that can be used to address the full range of developmental disorders that are found to be overlapping much of the time in any sample of children. Although similar in spirit to the older term of minimal brain dysfunction (MBD), in that it closely links neurology with behavioral difficulties, ABD as proposed here differs in several ways. In support of the ABD conceptual framework, first, we consider the ABD concept in terms of its superiority to the older notion of MBD. Second, we provide a brief review of the burgeoning literature on the overlap of the various developmental disabilities. Third, we review some of the scientific literature that supports the ABD concept. Our sole purpose in proposing this concept is to initiate dialogue and debate on several critical issues across a wide variety disciplines. Hence, this article is not intended to be a definitive statement of a rigid perspective. It reflects neither a nonmalleable philosophical position, nor any type of condemnation of other perspectives. It does, however, reflect a data-based and philosophical trend visible in the field of learning disabilities, as well as the broader area of childhood developmental disorders.

Genotype-environment correlations for language-related abilities: implications for typical and atypical learners

Recent behavioral genetic research has shown that genetic propensities are associated with individual differences in experiences, and thus, what may appear to be environmental effects can reflect genetic influence. This study examines passive genotype-environment correlations (GECs) for language-related abilities by comparing environment-child language associations in adoptive and nonadoptive families. The results provide evidence for the genetic mediation of the association between home environmental variables, such as the provision of toys and games, maternal involvement, and degree of intellectual/cultural orientation with children's language-related abilities. Developmental changes in passive GECs are considered, and the implications for typical and atypical learners are discussed.

Epidemiological and offspring analyses of developmental speech disorders using data from the Colorado Adoption Project

Although the adoption design is the most powerful method to disentangle nature and nurture, it has not been applied previously to developmental speech or language disorders. The present study examined the speech outcomes of 156 adopted and nonadopted children at varying risk for speech disorders based upon self-reported parental speech history. The sample consisted of four groups: (a) 16 adopted children with an affected biological parent; (b) 19 adopted children with an affected adoptive parent; (c) 31 nonadopted children with an affected natural parent; and (d) 90 low-risk adopted and nonadopted children with no parental speech disorder history. Results revealed that 25% of the children with a genetic background of speech disorder displayed questionable speech, language, or fluency skills at age 7, in comparison to 9% of the children with no known genetic history. Logistic regression analyses indicated that positive biological parental background was the best predictor of offspring affected status. The child's Full-Scale IQ and the HOME Scale of family environment were not significantly associated with speech outcome. These results provide additional evidence that genetic factors contribute importantly to the vertical transmission of some developmental speech disorders of unknown origin.

The genetic basis of persistence and recovery in stuttering

Although past research has provided evidence of a genetic component to the transmission of susceptibility to stuttering, the relationship between the genetic component to stuttering and persistence and recovery in the disorder has remained unclear. In an attempt to characterize this relationship, the immediate and extended families of 66 stuttering children were investigated to determine frequencies of cases of persistent and recovered stuttering. Pedigree analysis and segregation analysis were used to examine patterns of transmission. The following questions were investigated: 1. Is there a sex effect in recovery from stuttering? Here, we sought to test the hypothesis that females are more likely to recover than males, leading to the change in sex ratio from approximately 2:1 males to females close to onset of the disorder, to 4 or 5:1 in adulthood. 2. Is persistence/recovery in stuttering transmitted in families? If recovery/ persistence appears to be transmitted, (a) are recovered and persistent stuttering independent disorders?; (b) is recovery a genetically milder form of persistent stuttering?; or (c) is persistence/recovery transmitted independent of the primary susceptibility to stuttering? Results indicated sharply different sex ratios of persistent versus recovered stutterers in that recovery among females is more frequent than among males. It was found that recovery or persistence is indeed transmitted, and further, that recovery does not appear to be a genetically milder form of stuttering, nor do the two types of stuttering appear to be genetically independent disorders. Data are most consistent with the hypothesis that persistent and recovered stuttering possess a common genetic etiology, and that persistence is, in part, due to additional genetic factors. Segregation analyses supported these conclusions and provided statistical evidence for both a single major locus and polygenic component for persistent and recovered stuttering.

Genetics of stuttering: a critical review

The fact that stuttering runs in families has been documented over a long period and has led to speculations and research about the role of a genetic component to this disorder. Although the genetic factor cannot be proved by familial aggregation and twin studies alone, such research has continued to provide support for a relationship between stuttering and genetics. The purposes of this article are to review and critique the research in this area. The article first assesses research methodologies that have been employed in familial studies of stuttering. It proceeds to review and critique incidence, twin, and aggregation studies. In addition, it includes sections on subgroups, genetic models of stuttering, and implications for future research as well as for clinical work. With a focus on improved methodology and recent findings, a current perspective on our knowledge of the genetic component to stuttering is provided. Among other conclusions, the article emphasizes that failure to consider epidemiologic factors has probably biased previous results regarding the genetics of stuttering. New preliminary data also appear to provide evidence that spontaneous recovery and chronicity are influenced by genetic factors. Generally, however, the review of incidence and twin studies, as well as of evidence for the various inheritance models, confirms previous conclusions about the interaction between genetic and environmental factors in stuttering.