It is often reported that deaf children have difficulties with Executive Functions (EF), often manifesting as behavioral problems. A lot of researchers have attributed these difficulties with EF to auditory deprivation. However, in this paper, Hall et al. provided evidence for an alternative account: auditory deprivation is not a primary cause of EF problems in deaf children, whereas the primary cause might be the deprivation of early exposure to a natural sign language.
BRIEF Parent Report Questionnaire as a measure of EF
In this study, Hall et al. used the Behavioral Rating Inventory of EF (BRIEF) as a measure of EF. BRIEF is an 86-item questionnaire designed to quantify the prevalence of concerning behaviors related to different aspects of EF. It is designed for use with children between the ages of 5 and 18 and should be filled out by their primary caregiver or teacher. There is a global summary index as well as scores on 8 specific subscales organized into 2 other summary index (Figure 1). It is widely acknowledged that behavioral regulation and metacognition are important indicators for EF.
BRIEF is a normative test: the score is based on a large and representative sample of typically developing children’s score. The normalized score has a mean of 50 and a standard deviation of 10. A score of 60 (1 SD above mean) is defined as having “elevated risk” and a score of 65 (1.5 SD above mean) is defined as “clinically significant.”
Auditory Deprivation Hypothesis
Previous studies using BRIEF to investigate deaf children’s EF all reported EF deficits: they have higher scores than typical hearing controls or have a higher risk of falling in the “elevated risk” range. These problems were attested in deaf children with and without cochlear implant across a range of ages from preschool through adolescence in different education setting (both mainstream school and specialized school for the deaf).
One prevalent view on the origin for EF deficit in deaf children is that the lack of auditory experience will affect higher-level neuro-cognitive skills. For example, it is conceivable that lack of auditory would largely limit the exposure to sequential signals, which is crucial to EF development.
Language Deprivation Hypothesis
However, this study offers an alternative explanation for the EF deficit of deaf children found in the previous studies: roughly 95% of deaf children lack exposure to natural human language in their early months/years of life. It might be the lack of early language exposure that hinders their EF development.
The researchers asked parents of 42 Deaf children, who receive natural sign language exposure from birth, and 45 hearing children to fill out BRIEF questionnaire. The families included in the two samples don’t differ significantly from each other in race and ethnicity or other Socio-Economic Status variables like family income and parents' education level. Nor are the samples here significantly deviant from the normative sample used to establish BRIEF score.
As shown in Figure 2, neither group’s mean exceeded the expected value of 50 on any subscale or summary index. The two groups don’t differ from each other on any of the subscales, except for Working Memory and Plan/organize. When comparing relative risk to be in the “elevated” range, the Deaf native signers do show significantly greater risk than the hearing participants on the Inhibit and Working Memory subscales, although the difference might be driven by surprisingly low risk indicated in the hearing sample.
Whereas all previous studies reported significant behavioral problems in deaf children, the Deaf native signers in the present study had mean scores indicative of healthy, normative, age-typical EF. Specifically, their scores did not differ from the typical mean of 50, and they did not have significantly increased rates of either elevated or clinically significant scores relative to control group. The present findings go against what the auditory deprivation hypothesis would predict, that is, Deaf native signers should be equally at risk of developing problems with EFs, because they too experience auditory deprivation. In fact, their predicted risk should have been even greater, given that the majority of the Deaf native signers do not regularly use hearing technology. However, this prediction is not supported by the results of the present study.
The present findings are consistent with language deprivation hypothesis as an alternative account.The early exposure to sign language, which is the only manipulated difference between the current study and previous studies, seem to have protected the Deaf children from EF deficits.
The result is not unexpected. First of all, EF deficits in Deaf children without sign language exposure might have arisen from the lack of a way of properly communicating their needs, intentions and emotions. They would therefore also have fewer opportunities for incidental learning by observing communication between others, which is an important source for understanding of social/cultural standards of behavior. Secondly, the results are consistent with the evidence from research on spoken language development from a theoretical perspective. Exposure to the patterns that characterize natural language (e.g., rapid temporal processing, long-distance dependencies, rich hierarchical structure, abstraction from sensory perception to mental representation, etc.) might in fact train neural circuits that are used not only in language processing, but also domain-general cognitive functions. Since it is established that sign language also feature these patterns, it is a well-motivated hypothesis that abstract structure of sign language can benefit Deaf children’s general cognitive skills besides the mastery of language itself.
To conclude, Hall et al. compared Deaf children from Deaf families, who have been exposed to a natural sign language from birth, with age-matched hearing children control, on their scores from the BRIEF EF questionnaire. Their results show that the EF scores for Deaf native signers are age appropriate and are not significantly different from the hearing controls. These results indicate that auditory deprivation is not a primary cause of EF problems in deaf children and suggest that early exposure to a natural sign language “protects” deaf children from difficulties with EF.