NOT all bilinguals are created equal.

New research here has uncovered differences in brain activity which separate people who have a knack for picking up a second language and others who have more of a struggle doing so.

'It's as though one group can engage their brain to help them do so more efficiently, while the other group cannot,' said Dr Michael Chee, the main researcher in the study.

'There appears to be some biological underpinning in being able to pick up a second language.'

The work - which has been published in the world-renowned Proceedings of the National Academy of Sciences - could also help point the way towards how best to teach the language laggards.

Dr Chee and colleagues from SingHealth's cognitive neuroscience laboratory collaborated with a scientist from the Institut National de la Sante et de la Recherche Medicale in France, which is comparable to the National Institutes of Health in the United States.

They tested 30 adults - high achievers who had done well throughout school. Among them, one group had also excelled in Chinese (equal bilinguals), while the other had done poorly (unequal bilinguals).

They were given a number of unfamiliar French words to remember briefly, while their brains were scanned using magnetic resonance imaging (MRI) to map the brain activity engaged in the work of short-term memory.

While both groups appeared to perform the task equally well, the MRI scans painted a different picture.

They found that as the memory demands increased, the equal bilinguals activated more prominently a region on the left lower frontal lobe of their brains called the left insula - an area believed to be involved in speech rehearsal and the temporary storage of verbal contents.

Interestingly, those in the group who achieved the highest Chinese scores were also the ones in whom this brain area worked the hardest, an indication of its importance.

'It appears that the equal bilinguals process unfamiliar words in a way which helps them to incorporate the words into their long-term memory,' said Dr Chee.

Since the equal bilinguals seemed to rely on internal vocalisation of sounds to remember new words, he suggested such techniques might be effective in teaching those who were poorer in the language.

In those who were weak in Chinese, not only was the left insula under-utilised, a different frontal region was also turned off.

Called the anterior medial frontal region, this is part of a 'default network' which is actually more active when the brain is at rest.

The fact that the unequal bilinguals had to deactivate this part of the brain more indicates that they had to concentrate more to achieve the same results, he said.

But whether the differences in brain activity are innate, or take place depending on how people go about the learning process is still unclear.

'The extent to which such processing differences are the cause or consequence of impaired second-language attainment remains to be explored,' wrote the researchers in their paper.

Nonetheless, Dr Chee hopes that this will help to remove the stigma placed on those who do not do well in their second language.

'Those who are struggling with Chinese may not simply be lazy,' he said.

'Further research could help us to develop ways of determining if a child will have difficulties that go beyond mere lack of trying.'