A goal shared by all parents of congenitally deaf children is for their child to achieve language competencies that provide a foundation for nurturing, education, and engagement in society. Today, even against a backdrop of miraculous technological advances and an increasing sophistication in our understanding of human capacity for language acquisition, we fall short of being able to provide a prescription for individual deaf children that will guarantee spoken language competencies. In the absence of a definitive solution, we must rely on rigorous research to make correct inferences in ascribing best practices for parents with deaf children.
Sound scientific research evaluating the effects of an intervention is predicated on random selection or assignment to treatment and control groups. This ensures that each participant or subject has an equal chance of being placed in any group. Random assignment of participants helps to ensure that any differences between and within the groups are not systematic at the outset of the experiment. Thus, any differences between groups recorded at the end of the experiment can be more confidently attributed to the experimental procedures or treatment.1
The Geers et al study violates this basic tenet of research design. The incorrect assumption made by Geers et al is that all of their subjects have an equal potential to develop auditory and spoken language skills, or more accurately that this potential will be normally distributed across the no sign, short-term sign, and long-term sign groups. However, the authors grouped the children by their experiences with spoken language and manual communication after the parents and children had already chosen a communication strategy. The reality is that deaf children who are not achieving gains in speech and spoken language skills are recommended to augment spoken language skills with some form of manual communication. The selection bias evident undermines the subsequent comparisons made across these groups.
Baseline data presented in Tables 1 and 2 support this assertion. On the Auditory Perception Test, the long-term sign group received the lowest scores (5.8), followed by the short-term sign group (7.0), with the no sign group showing the best scores (9.8). On the Speech Recognition in Quiet test (before cochlear implantation), the long-term sign group had the lowest and least variable scores (7.5; 1.3–18.8) compared with the no sign group (16.3; 5.0–50.0), who showed the highest scores with the greatest variability; the short-term sign group was intermediate (15.9, 2.5–22.5). These data indicate the sign exposure groups were experiencing profound difficulty with auditory perception and speech identification. It will surprise no one that children with better auditory perception skills and speech identification skills at the outset will be the children who end up with the best auditory language scores.
Researchers and editors alike must be vigilant in putting forth rigorous research that address the factors that limit language potential in deaf children with CIs. Publishing research with inherently flawed research designs is a disservice to all parents who want their deaf children to flourish.
CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.