Tuesday June 3 2014
Bilingual people scored better in intelligence tests
"Learning a second language can have a positive effect on the brain," BBC News reports after a Scottish study found that participants who spoke two or more languages tended to perform better in intelligence tests than people who only spoke English.
The researchers looked at a group of 853 people who had been given intelligence tests in 1947 at the age of 11 and were then retested when they were in their 70s. They were asked if they had learned any additional languages and, if so, when they had acquired the language and how often they used it.
Almost a third of people spoke a second language. The researchers found that people speaking two languages (bilingual) performed significantly better than predicted from their baseline cognitive abilities at the age of 11. The strongest associations were seen in tests of general intelligence and reading.
A significant strength of the study is its timescale – tracking people over the course of seven decades is no mean feat, although this was done retrospectively. However, the study did not assess whether participants had cognitive impairment or dementia, so it cannot tell us whether being bilingual is protective against the development of these conditions.
Still, learning another language is a good way of keeping the mind active, learning about different cultures and meeting new people, all of which can improve quality of life. Read more about how learning new skills can improve wellbeing.
Where did the story come from?
The study was carried out by researchers from the University of Edinburgh and was funded by Age UK.
It was published in the peer-reviewed journal, Annals of Neurology.
The story was covered appropriately by BBC News and the Daily Express.
The Mail Online, however, had a headline that was not representative of the study's findings, reporting that "extra languages can help prevent dementia", which is not what the study looked at.
The current study looked at the association of languages with cognitive functioning later in life.
To establish whether or not bilingualism prevents dementia, participants would have to be monitored for the rest of their lives.
However, an earlier study has suggested that being bilingual could delay the onset of dementia by several years.
What kind of research was this?
This was a retrospective cohort study looking at whether learning a second language other than English had an association with cognitive functioning at around the age of 70. It involved a relatively small group of people based in Edinburgh.
A retrospective study relies on data on exposures and outcomes that have been collected in the past (through medical records or as part of another study, for example) or through people remembering what happened to them in the past.
Data used in this way may not be as reliable as data collected prospectively (when the data is collected specifically for the study as events happen). This is because it relies on the accuracy of records made at the time, which can be inaccurate.
This study relies on information provided by older adults, who may already have some degree of cognitive impairment, which could introduce further inaccuracies.
What did the research involve?
The research was carried out on participants from the Lothian Birth Cohort 1936 (1,091 people) who took an intelligence test in 1947 at the age of 11, and were retested between 2008 and 2010 when they were in their 70s (853 people).
This cohort was unique in that they were native English speakers of European origin who were born, raised and living in and around Edinburgh. No immigrants were included.
The researchers say that by using this birth cohort, they were able to question whether learning a second language influences later cognitive performance after adjusting for childhood intelligence.
Intelligence testing consisted of a series of assessments, including:
- a range of fluid-type general intelligence tests, including letter-number sequencing
- a range of memory tests
- speed of information testing
- reading tests that examined the pronunciation of 50 irregular English words as part of the National Adult Reading Test (NART)
- verbal fluency testing, where participants were asked to say as many words as possible beginning with the letters C, F and L, with a one-minute timeframe for each letter
- the Moray House Test, which mainly tests verbal reasoning skills
It is unclear if the intelligence tests performed were the same as those carried out on participants when they were 11.
Bilingualism was assessed using a questionnaire where participants were asked whether they had learned any languages other than English, how many, and at what age.
They were also asked how often they used the languages (daily/weekly/monthly/less than monthly/never) across three areas: conversation, reading and media.
The researchers were interested in:
- the age of additional language acquisition (never/early/late)
- the number of languages (monolingual/bilingual/multilingual)
- the frequency the additional language(s) were used (no second language/no active use/active use)
In their analysis, the researchers adjusted the results for childhood intelligence, age at time of testing, sex and social class.
What were the basic results?
Of the 853 participants who completed the intelligence retesting between 2008 and 2010, 262 people (30%) reported having learned at least one other language to a level that allowed them to communicate.
Of these, 195 learned the second language before the age of 18 (though only 19 [2%] before the age of 11) and 65 learned it after this age.
The researchers report that 160 people knew two languages (bilingual) and 85 people knew three or more languages (multilingual).
The researchers found that people who spoke two languages (bilingual) performed significantly better than predicted from their baseline cognitive abilities. The strongest associations were seen in tests of general intelligence and reading.
The cognitive effects of bilingualism showed a consistent pattern, affecting reading, verbal fluency and general intelligence to a higher degree than memory, reasoning and processing speed.
Other results of note are described below.
Age of language acquisition
For early language acquisition, significant positive associations were found in the tests for general intelligence and reading. For late language acquisition, significant positive associations were found in the tests of general intelligence, processing speed and reading.
Number of languages
Bilingualism showed a significant positive association with tests of reading, while multilingualism showed significant positive associations with general intelligence, reading and verbal fluency.
Frequency of use
For passive bilingualism (no active use of the language for the past five years), the main associations were seen in the tests of general intelligence, reading and verbal fluency. For active bilingualism (use of the language in the past five years), the main associations were seen in the tests of general intelligence and reading.
However, there was a significant association between childhood intelligence and performance at the age of 73 for the active group on the Moray House Test – a significant effect of active bilingualism was only found for lower childhood intelligence.
In terms of the type of bilingualism, different effects were seen for early versus late acquisition depending on childhood intelligence. Overall, people with high intelligence appeared to benefit more from early acquisition, and those with low intelligence from late acquisition, but neither group showed negative effects.
Knowing three or more languages produced stronger associations than knowing two languages. There was little difference seen in the comparison between active and passive bilinguals, which the researchers say might be a result of the low frequency of use of the second language, even in active language users.
How did the researchers interpret the results?
The researchers concluded that their results suggest a protective effect of bilingualism against age-related cognitive decline independent of childhood intelligence, including in those who acquired their second language in adulthood.
In discussing the findings, lead researcher Dr Thomas Bak is reported in the media as saying: "These findings are of considerable practical relevance. Millions of people around the world acquire their second language later in life. Our study shows that bilingualism, even when acquired in adulthood, may benefit the ageing brain."
Overall, this study suggests an association between cognitive functioning later in life and having learned another language or languages.
A strength of the research is that it took into account childhood intelligence, which previous studies are not reported to have accounted for.
There remain some important limitations, however:
- Bilingualism was assessed using a questionnaire and not by proficiency testing, which may have biased the results. It is possible that some participants may have overestimated their ability to speak languages other than English.
- The researchers adjusted the results for childhood intelligence at age 11, but this may not have fully accounted for the person's overall cognitive ability and educational level in later childhood and adulthood. Also, despite adjusting for age at testing, sex and social status, there may be other hereditary, health and lifestyle factors at play that, taken overall, make it difficult to know whether acquiring and using a second language in itself has a direct and independent effect on cognitive ability.
- The researchers report that the birth cohort was homogenous, so findings from this study may not be generalisable to a different group of people (people who have migrated to another country, for example). Also, the study was carried out among a relatively small group of people based in Edinburgh, so the results should be interpreted with caution when generalising to other populations.
- The study did not assess whether participants had cognitive impairment or dementia, so it cannot tell us whether being bilingual is protective against the development of these conditions.
While it may seem a commonsense proposition that keeping the brain active will protect against dementia, the evidence is inconsistent. Various brain training exercises have been studied with varying degrees of success.
However, there is evidence that keeping the mind active at any age does improve mental wellbeing, whether it's learning a new language, teaching yourself to cook, or going to a museum. Read more about learning for mental wellbeing.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.