In a conversation about bilingualism, language, and cognition it's always a question if bilingual children are susceptible to learning difficulties or disabilities. The short answer is no.
Bilingualism by itself is not known to cause any learning difficulties or disabilities. Learning more than one language is something all children and adults should pursue.
That being said, in this article, we aim to look at some of the learning difficulties and disabilities associated with bilingual children. The aim is to shed light on what learning difficulties and disabilities are with respect to bilingual children, and what are some things you can do to aid your child in their journey to be bilingual. These are just surface-level inputs and if your child does have any specific medical conditions, you should see a speech-language pathologist for the most accurate assessment.
What are learning difficulties and disabilities?
Learning difficulties and disabilities can often be seen used interchangeably, although understandable, they aren't the same. Learning difficulties are referred to an underlying condition that only affects a certain aspect of an individual's life and won't be present in other aspects. Dyslexia is an example of such a condition where the condition only affects specific areas of an individual's life and doesn't affect the overall IQ. Learning disabilities would be referring to a condition that affects learning and intelligence across all areas of life. Down syndrome would be a condition that falls into this classification since it affects health, IQ, life skills, and physical condition as well.
A child with such conditions has issues with reading spelling and writing. These are in all senses language problems. This has nothing to do with how smart your child is, most people with learning disabilities have an above-average level of intelligence.
The conditions that fall into either of these classifications are by no means caused because of bilingualism.
Causes of Learning Difficulties and Disabilities
Learning disabilities are brain disorders. Both bilingual and monolingual children can have these conditions by birth or may develop them in early childhood. Irrespective of the number of languages that the children learn, special language and cognitive processes will be required to support their language learning.
There is a high chance of your child having a learning disability if someone in your family suffers from a similar condition.
The information available
Most bodies of research related to bilingual children currently available to us a centered around neurotypical candidates. In recent years the focus has shifted to include children speaking two languages who have language disorders, but rarely have inclusions that consider cognitive psychology. Other disorders like Autism, Williams Disorder or Down Syndrome barely have any relevant research behind them with regards to a bilingual child. Therefore, to understand bilingualism in children with learning disabilities, we can only refer to the research available to us today.
Bilingualism is unique for every individual
Being bilingual is variable for all individuals and so is bilingual language development across the board. This is true for both a bilingual and monolingual child. The first important factor is timing. This means when the second language was introduced to the child. Simultaneous bilinguals learn two languages at the same time essentially from birth (usually a native language and a majority language), sequential bilinguals learn their two languages one after the other. Other factors include where the language is spoken, who speaks to the child in these languages, how similar are the two languages to each other and what is the social acceptance of a certain language. The quality and quantity of exposure is also and essential factor, a child will naturally gravitate to a language that they hear more often and have a better set of interactions in.
Even with the large body of research, irrespective of the language and cognitive ability, we do not know how to best support bilingual language development. A popular strategy is the one parent, one child method wherein one parent speaks one language and the other speaks a different language. This is not a practical for all families since they may be bilingual. There is also the factor of child not responding in the language that you speak in. Each experience is truly unique, and in order to truly learn they need frequent exposure. This is especially important for children with language leaning and cognitive disabilities. You also need to provide high quality input with interactive and naturalistic environments. General simulation experiences like imitating, modelling, exaggeration are particularly useful irrespective of the language being taught.
Bilingualism, language and cognition in neurotypical individuals
Simlultaneous bilinguals with adequate high quality exposure will acquire both languages in approximately at the same time as their monolingual children. This means that a milestone like speaking the first words, would occur at the same time. This doesn't mean that bilingual language development looks the same as monolingual language development. If you observe children, monolingual children will have a greater vocabulary than bilingual children for each of their languages but the combined vocabulary of bilingual children will be often greater than their monolingual peers.
Another difference between bilingual children and monolingual children is that a bilingual children experience language transfer. This is wherein the aspects of one language affect the understanding of the other language. While this is positive in cases where the two languages are similar to each other (cat is chat in French) we might see some syntax errors where pronouns precede the nouns in some and succeed nouns in others. Based on the research available to us, we can expect to have language transfers in children with language and cognitive impairments as well.
Sequential bilinguals have a different development profile than that of simultaneous bilinguals. Their learning of the new language may not always lead to fluency in the second language. This would also depend on quality and quantity of input at that stage. Even in previously monolingual and bilingual adolescents, who have access and cognitive ability to learn a new language, their motivations to learn this new language will be a point of contention. This can also lead to their native language becoming weaker as their exposure to the new majority language increases.
Bilingualism and Specific Language Impairment
Children with Specific Language Imapairment (SLIs) have language learning disabilities like language delay, which aren't really are not major cognitive issues or disabilities. Research has shown that bilingual children with SLI make the same errors as monolingual children with the same condition. For example, using auxilliary verbs in English may be an issue for both irrespective of the number of languages that they are being exposed to. When bilingual children with SLIs are compared to monolingual children with SLIs are compare, they make the same errors. In a case where language matched bilingual children are compared, they exhibit a similar error frequency.
These findings taken together only reinforce that bilingualism is not detrimental to language learning in children with SLIs and they can successfully become bilinguals. In addition, bilingual children will exhibit their impairment across all languages that they learn however these errors may differ based on the language being learnt. Raising bilingual children with SLIs is the same a raising monolingual children with SLIs form a learning and cognitive standpoint.
Bilingualism and Down Syndrome
Down syndrome specifically has shows to cause learning disabilities from minor to severe in nature. Their cognitive impairment leads to general learning difficulties as well as specific language learning problems. So they will experience a language delay relative to their age. While each individual is different, there is an identifiable pattern of language strengths and weaknesses in monolingual children. Firstly, their ability to understand a language is often stronger than their ability to speak it. Second, grammar is harder for children with Down Syndrome than vocabulary.
So you may wonder how bilingual children with Down Syndrome fare with all the research available to us? There's evidence to show that children with Down Syndrome can successfully bilingual and trilingual as well. Simultaneous bilinguals show a similar set of strengths and weaknesses in both the languages that they learn. Lastly, the dominant language skills of simultaneous bilinguals with Down Syndrome are consistent to monolingual bilinguals with Down Syndrome at the same mental age. So being bilingual does not present any specific disadvantages in terms of language learning. There is not much information on sequential bilinguals with Down Syndrome as of now.
Invariably, more research muct be conducted with bilingual and monolingual patients who have language difficulties of disabilities. Especially children with language and cognitive disorders must be studied in larger numbers across educational inputs and geographical locations. Sequential bilingualism in itself must be studied more in itself to see how a bilingual person's language systems develop. There should also be research into if bilingualism positively affects cognitive abilities for individuals with learning difficulties and disorders. Specific learning methods must be studied as well.
Given the information available to use now, we can derive the following conclusions:
Families should lead decisions if they want to teach their child a second language. If a child with learning or cognitive disabilities needs to learn two languages, the focus must be to condition this learning rather than reducing the number of languages.
A high quality and quantity of input is irreplaceable when it comes to learning a new language. For a child with learning or cognitive disabilities will have a certain unique set of issues for all of their languages.
Bilingualism does not affect the general characteristics of weaknesses and strengths in learning a new language in children with learning or cognitive disabilities.