Researchers have found that when a person who speaks two languages experiences brain damage leading to a language condition called aphasia, the second, less dominant language can be used to transfer knowledge to the primary one, helping with rehabilitation.

The National Aphasia Association defines aphasia as “an impairment of the ability to use or comprehend words, usually acquired as a result of a stroke or other brain injury.”

When a bilingual person acquires aphasia, the two languages can be disrupted, making language rehabilitation quite difficult.

However, according to researchers in Montréal, bilingualism can actually be used as a tool in aphasia recovery. They published the results of their review in the Behavioural Neurology Journal.

They say that focusing on the less proficient language, not the dominant one, results in a “transfer effect” to the primary language. Similarities between the two languages, they say, promote this language transfer.

Correlations between syntax, phonology, vocabulary and meaning aid language rehabilitation, but the researchers say working on “cognates” – similar words in both languages – help the most with language transfer.

For example, they note, the word “table” in French has the same meaning and sound as the word in English, thus helping with the retrieval of the word for people who speak both languages.

However, they note that “non-cognates” – words that sound alike but do not share the same meaning – can derail rehabilitation for a person with aphasia.

Another approach that focuses on word meanings – semantic properties – can also help with word recovery in both languages.

For example, when a language therapist prompts the patient to associate the word “dog” with the concepts of “pet,” “four legs” and “bark,” the French word for dog – “chien” – is activated. The researchers note “chien” will be retrieved more easily than saying the word “dog.”

Dr. Ana Inés Ansaldo, a quadrilingual researcher at the Research Centre of the Institut universitaire de gériatrie de Montréal (IUGM), says:

In the past, therapists would ask patients to repress or stifle one of their two languages, and focus on the target language. Today, we have a better understanding of how to use both languages, as one can support the other. This is a more complex approach, but it gives better results and respects the inherent abilities of bilingual people.”

The researchers end their review by noting that the degree of “structural overlap” between languages, as well as the type of therapy approach, plays a role in the potential for therapy between primary and secondary languages.