Researchers will be recruiting 700 people aged between two and 80 to take part in the £750,000 programme.
Prof Virginia Gathercole said the obvious benefits included being able to converse and to participate in two cultures.
But she said there was also evidence of non-language benefits, such as the ability to protect the brain from ageing.
"The very act of being able to speak, listen, and think in two languages and of using two languages on a daily basis appears to sharpen people's abilities to pay close attention to a aspects of tasks relevant to good performance," she added.
"Running two parallel language systems throughout life has had positive benefits in a number of ways"
Prof Virginia Gathercole, Bangor University
Research carried out already had also shown having two languages helped protect against the decline in the brain's abilities when ageing," she added.
"We already know that language processing is one of the most complex activities that our brains carry out.
"Running two parallel language systems throughout life has had positive benefits in a number of ways," she added.
One multilingualist, Phillip Hughes, 62, travelled widely with his work as a teacher before his retirement. He said he found having two languages handy, especially when he had to learn another one, German while living in Swizerland.
Case study - Phillip Hughes, 62
I think being able to speak two languages has been of benefit, especially when I had to learn German when I worked in Switzerland.
I learned it quickly and they said my pronunciation was good.
At home I spoke English as my mother spoke English, but outside I would speak Welsh (and I also spoke Welsh in my sleep apparently).
I want my children to grow up speaking more than one language, and to understand that it is important to speak more than English - especially if you go off the beaten track.
He grew up in an English-speaking household, but spoke Welsh to his friends and in the wider community, and was adamant that his children should also have language skills.
Dr Enlli Thomas, who is collaborating on the project, said there was evidence from Canada that being bilingual "may provide some protection against age-related memory loss".
The Bangor research team are looking for people who are bilingual in Welsh and English and monolinguals - or those who speak only one language - aged over 60 to take part in the research.
Participants take part in a set of simple language tests and then carry out on-screen puzzles and tasks, similar to "brain games" played on hand-held games consoles.
The researchers are looking for people who grew up in homes where only Welsh was spoken, where both Welsh and English were spoken, and where only English was spoken.
The research can be carried out either at the university or a researcher can visit the participant.