How HANDy are baby signs? A systematic review of the impact of gestural communication on typically developing,hearing infants under the age of 36 months: Response to Howard and Doherty-Sneddon’s commentary

We are pleased that our review of baby sign intervention has generated such thoughtful reflections. As researchers with clinical backgrounds in human communication disorders we strive to apply scientific knowledge to help our clinician colleagues, parents, and decision-makers make appropriate decisions about language related issues. This was the primary motivation driving the need for an updated review of the evidence related to baby sign for infants with normal hearing, a subject that remains highly topical. Clinicians are aware that they have limited time with their pediatric clients and that it is essential that the interventions they undertake are effective. Parents are interested in activities that will be enjoyable and educational for their young children. Decision-makers have a responsibility to fund interventions that make a positive difference in the lives of young children. The primary intent of our systematic review on the impact of gestural communication was to examine the effectiveness of this intervention for infants and their caregivers to help these groups make informed decisions.

We wholeheartedly agree with the authors of the commentary on our review, Lorraine Howard and Gwyneth Doherty-Sneddon, that there is a need for additional, methodologically strong research to clarify the nature of gestural sign intervention and to examine its effectiveness. Within human communication research there are a number of interventions, which are not amenable to rigorous methodological evaluations due to ethical or feasibility limitations. For example, researchers and clinicians are reluctant to withhold interventions from children with known difficulties. However, the effectiveness of baby sign programs with typically developing children can be evaluated through experimental studies using the gold standard of evaluation, the randomized controlled trial. Researchers would certainly be able to enroll a large enough sample size of normal hearing parents and typically developing infants for the study to be adequately powered to detect whether baby sign intervention affects children across various areas of communication development. In addition, it would be possible for researchers to be blinded to the allocation of participants to the intervention and control groups during data collection and analysis of the results. If we are to appropriately assess the effectiveness of baby sign or other gestural interventions for infants with normal hearing, as is needed, it will be important to apply well-developed research techniques from our colleagues in medicine and epidemiology (Haynes, Sackett, Guyatt, & Tugwell, 2005). We appreciate the additional comments from Howard and Doherty-Sneddon and hope that this discussion will heighten interest in conducting empirical research in this continuing area of interest.

The authors of the commentary suggest that it is possible that some studies were not captured in our search given the different forms of baby sign currently in use. We think that it is highly unlikely that studies were missed given the comprehensive search strategy that was adopted with the assistance of two library information specialists in systematic reviews. We considered any study for inclusion that reportedly used any form of baby sign intervention even if it was anchored in established sign language systems as long as these were carried out with children with normal hearing, our study group of interest for the current review. If such studies were available to demonstrate the effectiveness of symbolic gestures, it is very likely that they would be widely known and well popularized on websites promoting these interventions. Furthermore, there is no indication that one or two more studies using a more sociocultural sign approach would produce different conclusions in addressing the question of the effectiveness of these interventions for typically developing children.

We appreciate the useful comments that the authors bring forward, particularly in highlighting that there is a body of literature on the importance of gestures for early communication development as well as their interesting observation about how culturally Deaf parents phase in gestural language with their children. However, in our view, while this is an interesting discourse, such a discussion is beyond the intent of our review, which was to examine the evidence for the effectiveness of baby sign for children with normal hearing of hearing parents. We acknowledge, as clearly noted in the introductory section of our review, that there is research supporting the advantages of gesture use in facilitating parent–child interaction and early communication development (Miller & Lossia, 2013; Olson & Masur, 2013; Rowe & Goldin-Meadow, 2009). Nevertheless, for the reasons detailed in our report, despite the relatively long history and apparent popularity of baby sign intervention, there remains no conclusive empirical evidence supporting its effectiveness. We are also in full agreement with Howard and Doherty-Sneddon, as stated in the concluding remarks of our report, that there is no evidence that introducing sign language of any form in infancy has negative effects.

Howard and Doherty-Sneddon’s commentary continues the important conversation regarding the value of symbolic gesture interventions with infants who have normal hearing. The addition of the psycholinguistic perspective is important and adds to the complexity of the issue. It is this continued interdisciplinary conversation, paired with methodologically rigorous evaluation that will help to improve our knowledge regarding the impact of gestural interventions.