The brain of a newborn is designed for early acquisition of language. Indeed, language acquisition proceeds without explicit training on the part of the already competent language users. Children naturally come to be fluent in whatever accessible language(s) they are surrounded by and exposed to on a regular and frequent basis. The language or languages the child acquires during these early years are called first languages. Around five years of age, the plasticity of the brain begins to gradually decrease. A child who has not acquired a language by that time (often called "the critical period") runs the risk of not acquiring native-like fluency in any language [10–12]. As a result, the child becomes linguistically deprived. Linguistic deprivation occurs rarely among hearing children, and only in the most unusual circumstances, such as in children who have grown up without being surrounded by human language , or in children who have been denied language as an act of abuse .
The circumstances for deaf children are different. Spoken language is not accessible for many deaf infants and children. This is true even for children who have cochlear implants, because the success rate with cochlear implants is highly variable [15–17]. While many studies of the language and psycho-social development of implanted children conclude that cochlear implants are valuable, other studies of implanted children's language skills in daily communication beyond speech skills within a laboratory setting reveal that an alarmingly large percentage of implanted children are not receiving sufficient benefits and continue to demonstrate weakness in language competence. A closer examination of these studies finds that a significant number of these children do not communicate with ease in a speech-only environment even after years of rehabilitative training [[18–31], among others]. Assuredly, there are spectacular successes that have been reported in the literature cited here, but they do not represent the majority of deaf children, and unfortunately, even those very successful individuals often demonstrate some cognitive difficulties [32–34].
Sign language, on the other hand, is accessible to all deaf children, even to the deaf-blind child since there are tactile versions of sign language . Yet many deaf children are raised in a strictly speaking environment and are not offered sign language until after the age of five or not ever [36–38].
Harm to the individual from linguistic deprivation
Not having a solid foundation in any language - not being able to converse with native fluency and with complete ease - this is not all that linguistic deprivation encompasses. Linguistic deprivation carries with it a spectrum of problems beyond strictly language pathologies. Cognitive activities that rely on a firm first language foundation such as mathematics (since symbol manipulation is involved) and the organization of memory are then disordered or disrupted [38, 39]. Linguistic deprivation also diminishes one's educational and career possibilities, since the cognitive factor that correlates best to literacy is a foundation in a first language [40–52] - and without literacy one's professional opportunities are highly circumscribed. Additionally, linguistic deprivation leads to psychosocial problems due to the isolation and frustration one experiences from diminished linguistic and cognitive capability. This also results in the inability to express oneself fully, and to easily understand others completely [[53, 54], among many]. Clearly, linguistic deprivation constitutes a multi-faceted harm to the individual.
Harm to society from linguistic deprivation
Because many deaf people have been linguistically deprived at some level, epidemiological studies of deaf people have revealed some alarming and undesired statistics. Deaf people have a higher rate of illiteracy , imprisonment [56, 57] and unemployment [58, 59]. Illiteracy strongly correlates with high unemployment, poverty and poor health (often due to lack of access to information about good health choices and risky behavior). While poverty has negative effects even for hearing children , those effects are multiplied when the child is linguistically deprived, making the child even less likely to be able to participate constructively in society. We also find that deaf children and adults who cannot communicate with those around them are abused more frequently [61–63]. Victims of maltreatment, particularly in childhood, have a higher incidence of mental disturbance and risky behaviors, exacting additional costs on society [64–66]. Given these facts, it is predictable that linguistically deprived deaf people would have a higher incidence of imprisonment - either because they engage in criminal activity, sometimes under coercion , or because they cannot participate in defending themselves against accusations of such activities. All of these factors burden society. Further, the loss to society of the potential productivity of all these people is significant. Clearly, linguistic deprivation is harmful not only to the affected individuals, but to the society at large. Next, we discuss how this harm is embedded in current medical acts and practices.
Medical acts that harm
There are several medical acts that cause harmful linguistic deprivation for the deaf child.
First, failure to inform
Many medical professionals faced with the parents of a deaf newborn or newly deafened child tell them that there are two routes with respect to language and educational choices: the oral route (i.e., access to spoken language only) and the manual route (i.e., using sign language with the child). They then explain that the choice is up to the parents. Presented in this way, parents often think their choice is between their child speaking English or communicating using signs that are not understood by most people in the society. Unfortunately, to date, most professionals do not realize there is another choice, a bimodal choice (i.e. using sign language while at the same time promoting English/speech development).
Some professionals explicitly frame the parents' choice as a cultural choice . The child either grows up as a deaf person immersed among people who hear, or grows up like those deaf people they see signing on the streets or in the deaf programs they may have visited. The problem with this choice is that this choice is often based on a stereotypical view of deaf people and not on an adequate portrayal of well-functioning, well-adjusted deaf people who might also use sign language. Unfortunately, at this time, only a few medical professionals have the knowledge or training to give better advice. The result of this uninformed or misinformed advice is often unintentional harm to the child and family.
The vast majority of deaf infants (approximately 96%) are born to hearing parents, who often know very little about sign language or Deaf communities . These parents are in a state of vulnerability, grieving the loss of a normally hearing child and fearing what the future may hold (or not hold) if their child cannot speak like a hearing child . They might view sign as an inferior choice or a last resort [71, 72] and not fully understand that sign language is a human language with the linguistic complexity and expressiveness of spoken language. They might also fear their child will be stigmatized if they use a sign language . Furthermore, they might be afraid of trying to learn a new language at their age . In the absence of relevant information, many parents opt for the speech-only route because, without appropriate advice and information, they do not understand the risks of linguistic deprivation.
Medical professionals who work with deaf children and their families need to step forward and assume the responsibilities that the situation places on them. If they intend to give advice to their deaf patients about language development, they need to inform themselves about how some principles of first language acquisition might be more important for deaf children. Visual language skills can contribute to deaf children's language development (one can teach phonology to deaf children through sign language without using any sounds, for example). A deeper understanding of this would lead medical professionals to tell parents of deaf children that sign language offers them accessible language and prescribe this as a medical necessity.
Second, misinforming and coercing behavior counter to the child's welfare
Many medical professionals, faced with vulnerable parents of deaf newborns or newly deafened small children, offer the speech-only route as entirely different from the bimodal route. Frequently, they will urge parents to keep the child away from sign, offering the paradoxical justification that signing will be so "easy" that the child will lose motivation to learn to speak, and that the child can always learn a sign language later precisely because it is so easy . This advice to avoid sign language is comprehensive and extends through both home and school [76–78]. Sometimes, families are encouraged or actually required to sign an agreement to this effect . As a result, some parents will demand in their child's Individualized Education Plan at school that their child be removed from any access to sign language and be educated with speech/hearing only . Cochlear implant protocols that prohibit the use of alternative accessible language are causing linguistic deprivation in deaf children who do not acquire a first language by early childhood.
These professionals are acting under misapprehensions. There is no evidence to back up the claim that sign languages are easier to learn than spoken languages or that if a child learns a sign language, that child will lose motivation to work at gaining speech skills. Many young hearing children are exposed regularly and frequently to multiple accessible languages and acquire them both (or all) with little effort. Bilingualism and multilingualism have a range of cognitive as well as professional and personal advantages for anyone, deaf or hearing . If the deaf child is truly finding the spoken language accessible, there is no reason to expect that child to abandon acquiring the oral language simply because they are also acquiring a sign language. On the other hand, if the oral language is not accessible, then it is crucial that the deaf child acquire a sign language, since without it, the child will experience linguistic deprivation.
Certainly, the issue of accessibility of oral language with respect to the deaf child is a nuanced one. All implanted deaf children, for example, need intensive therapy or training in order to have a chance to access spoken language . And the question still remains whether the amount of access to speech that the implant might bring will translate into substantial qualitative and quantitative access to language, substantial enough to acquire it. This is because a cochlear implant bypasses the ear canal and transforms auditory information into electrical impulses that are directly delivered to the cochlea [30, 83]. As a result, accessing spoken language for the deaf child, takes effort and intervention. Still, children put out effort to learn new activities all the time - from those that are mostly motoric in nature such as walking or riding a bike, to more cognitively based activities such as drawing a tree or reading and singing. If a child experiences progress at and benefit from an activity, that gratification is sufficient to motivate further work at the activity. It is generally only in the face of no progress that children will quit at activities crucial to daily living.
The deaf child who signs experiences gratification, and the deaf child who makes progress in producing speech and in both speech-reading and aural comprehension also experiences gratification. There is no reason to think that these deaf children, particularly those who are making progress, cannot experience even greater gratification with bimodal language exposure and gain competency at both.
Third, abnegation of trust
Many deaf children raised in speech-only environments receive little to no accessible language. In the face of lack of progress or disappointingly low progress, parents may try to remain optimistic. They might be resourceful and try new rehabilitative techniques. They might be patient and encouraging to the child, hoping that it's just a matter of time. Medical professionals often condone and foster these parental behaviors because they, too, are invested in the success of the implant. Too often, the family does not realize that the child is experiencing severe difficulties in language development until the child is falling behind hearing peers in settings outside the home, often at school .
Some of these parents lose faith in their medical professionals and sometimes extend that lack of faith to medical professionals in general. They may not know where to turn. They suffer from indecision and stress that they might be failing their child. The result is a delay in facing the child's problem , often until the critical opportunity for language acquisition has passed. The abnegation of trust causes this delay, and such a delay is highly detrimental [43, 71, 85].