Copyright © 2007 by Paling, J. Critical Review: Does Baby Sign Language have a Positive Affect on the Language Development of Typically Developing, Hearing Infants of Hearing Parents? Jennifer Paling M.Cl.Sc (SLP) Candidate University of Western Ontario: School of Communication Sciences and Disorders This critical review examines the effects that introducing sign language to typically developing, hearing infants under the age of 36 months with hearing parents has on language development. Study designs include: systematic review, prospective cohort, and case study. Overall, research to date has failed to support claims that signing with typically developing hearing infants with hearing parents facilitates language development. Introduction Objectives The primary objective of this review is to All parents want what is best for their child. critically evaluate the existing literature regarding the Products and ideas that claim to advance children’s impact of baby sign language on language development leave parents wondering whether they development of typically developing hearing infants or not they are doing enough for their child. One with hearing parents. The secondary objective is to such idea, baby sign language, is quickly growing in propose evidence-based practice recommendations popularity in the media, on the internet and in the integrating the results into clinical practice. Finally, clinical setting. Some hearing parents worry that recommendations will be given as to how to improve introducing sign language will hinder their hearing the quality of articles dealing with this topic. child from developing spoken English. Conversely, another group of hearing parents are becoming Methods increasingly interested in using different techniques, such as introducing signs in addition to modeling Search Strategy spoken English to advance their hearing child’s Information and references were gathered language development. Many internet sites readily using a variety of databases, search engines and available to computer-savvy parents boast a long list internet sites. Databases used include: PubMed, of benefits including: reducing tears, tantrums, & PsycInfo, JSTOR, ERIC, and Medline. Keywords frustration, allowing babies to share their worlds, used include: baby sign, symbolic gesturing, sign strengthening the parent-infant bond, making language, typically developing, hearing children and learning to talk easier and stimulating intellectual language development. Articles were also located development (Acredolo & Goodwyn, 2006). Online using the references of reputable articles. The shopping has made it easier than ever to access baby Google Scholar search engine was used to find sign language products, leaving parents with the articles that were not available on the University of product and many questions. Western Ontario’s library databases by entering the Questions such as: “Should parents be article title or author name. Finally, the following encouraged to teach their hearing infants to internet sites were visited: www.signingbaby.com, communicate using signs? Does signing in infancy www.babysigns.com, www.babybumblebee.com and advance child behaviour and development as claimed www.sign2me.com. These websites were found by many commercially available products for using the Google search engine, from references in parents?” (Johnston, Durieux-Smith & Bloom, 2005, articles, and from word of mouth from clinical p.235). The growing popularity of introducing sign educators. These websites were reviewed for language to typically developing hearing children and background information, proposed benefits being the concerns of both eager and hesitant parents make advertised to the general public and product it important for Speech-Language Pathologists to information. know if there is evidence to support introducing baby sign language to typically developing hearing infants Selection Criteria with hearing parents and what affects it has on Articles selected for this critical review were language development. required to include typically developing hearing children under the age of 36 months with hearing parents. Any articles that focused on hearing children of deaf parents, atypically developing results were significant. Demographic variables, hearing children, or children with hearing such as socio-economic status, education levels or impairments were not included. occupations of the parents that were reported in Nelson’s (1973) study were not provided in Holmes and Holmes’ (1980) article. No attempt to identify or Data Collection isolate possible confounding variables was made Results of the literature search found the when interpreting Holmes and Holmes’ results or following types of articles which met the previously when comparing the two groups. Nelson’s (1973) mentioned selection criteria: one case study (Holmes attempt to isolate variables that may have had an & Holmes, 1980), one prospective cohort study effect on early language acquisition was described (Goodwyn, Acredolo & Brown, 2000) and one including variables found to effect the rate of systematic review (Johnston et al, 2005). language development (number of adults who interacted with the child and sibling constellation), Results along with variables found not to have an effect (educational background of the parents and number Holmes and Holmes’ (1980) case study of children in the family) (Holmes & Holmes, 1980). examined a typically developing, hearing male infant Holmes & Holmes (1980) made no attempt to of two hearing parents who were deaf educators and examine or control these variables in their study. The fluent in Siglish (American Sign Language [ASL] number of adults the infant interacted with was not that use English syntax patterns). This infant was stated so there is no way to conclude that the addition exposed to simultaneous spoken and signed English of Siglish is the reason for any or all of the reported from birth from his parents. He was also exposed to early language development. Additionally, although two deaf adults and numerous non-signing adults. Nelson (1973) stated that parental education did not Holmes & Holmes (1980) chose to do a have an effect, perhaps knowledge of language between group comparison, comparing their subject’s acquisition and language stimulation techniques results to those found in Nelson’s (1973) group of (which may accompany being a professional in deaf typically developing hearing infants who received education) could also have accounted for perceived language input exclusively through the auditory benefits in Holmes & Holmes (1980). The fact that modality. Holmes and Holmes’ (1980) subject the parents are educators of the deaf mean that the acquired his first ten words (signed and spoken) 3.1 results of this study cannot be generalized to the months earlier than the mean of Nelson’s group. general public, making it difficult to draw Looking at spoken words only, Holmes and Holmes’ conclusions and find any relevant clinical (1980) subject acquired his first ten spoken words 2.1 applications. months earlier than the mean of Nelson’s (1973) group. He also acquired his first fifty words (signed Goodwyn, Acredolo and Brown (2000) set and spoken) 8.1months earlier than the mean of the out to evaluate whether encouraging typically males in Nelson’s (1973) study (Holmes & Holmes, developing hearing infants to use sign language 1980). It is important to note however that two would have any effect on verbal language children in Nelson’s (1973) study also acquired fifty development. They conducted a prospective words by fourteen months (Holmes & Holmes, longitudinal study that began when infants were 11 1980). Looking again just at spoken words, Holmes months old and evaluated them using a variety of and Holmes’ (1980) subject acquired fifty spoken language measures at 15, 19, 24, 30 and 36 months. words 3.6 months earlier than the mean of the One-hundred and three infants were included in the comparison group. Holmes and Holmes’ (1980) study and infants were allocated to one of three subject started using two-word combinations between groups: sign training (ST), verbal training (VT) or 14.2 and 16.1 months of age whereas none of non-intervention control (NC) (Goodwyn et al, Nelson’s subjects had begun combining words by 2000). A between group design was used to 19.6 months of age. However, because the infant’s determine if there were group differences in language parents are proficient professionals in the field of development. deaf education and because the infant interacted Baseline measures, including the MacArthur frequently with two deaf adults, the results of this Communicative Development Inventory (CDI) and a case study are not easily generalized. fifteen-minute language sample were taken before the Although Holmes and Holmes (1980) study began to determine if there were any concluded that the subject had accelerated language differences between groups (Goodwyn et al, 2000). acquisition compared with the norms, there were no Although Goodwyn et al (2000) reported that there statistical analyses done to prove whether or not their were no significant differences found between the groups on any measure, no statistical data was Other confounding variables such as provided to back up this statement. parental education level, or number of adults Goodwyn et al (2000) included the VT interacting with each child were not taken into group to control for potential training effects. They account. wanted to eliminate the possibility