Scientists at Bangor University are turning to babies for help in finding the secrets of learning language.
Esyllt understood far more than her mother realised
Psychologists at the university in north Wales have been researching how infants learn language skills and has already carried out tests on around 20 volunteers.
As a thank you to the babies from English and Welsh-speaking families, they issued them with L-plate T-shirts - with a D for Dysgwyr, the Welsh word for learner, for the future Welsh-speakers.
But now the psychologists need more recruits to help them understand how and when infants learn different aspects of language.
Research officer Dr Satsuki Nakai said they used two methods to test when babies start to understand words.
"The first is the conventional method developed in the 1950s which looks at a baby's physical behaviour when presented with different words," she said.
"We would say words we know they will recognize like "daddy", "mammy" or "nappy" and then words we know they will not know like "mortgage" or "prime minister" and see how they react."
But they are comparing this method with a more modern test called Event Related Potential (ERP), which uses sensors to measure the baby's brain patterns.
The babies wear a special cap which measures their response to different words.
The babies' reaction to different words were tested
The pattern of their brainwaves then shows which words they recognize.
"The aim is to discover at what time they change from responding to the sound of a word to responding to the sound and meaning, like adults do," says Dr Nakai.
"We believe it is during the first year, but we hope to find out with these tests and compare which of these methods is the best to determine the timing."
Manon Lewis from Rhosgadfan near Caernarfon found her daughter Esyllt knew much more than she let on when she brought her for the tests.
"When I saw the brainwave patterns I realised that she understood much more than I thought she did.
"There were some big words that she definitely did not know, but although she is not talking yet, she understood a lot."
Researcher Pam Martin said they needed many more children to take part in the project which is being led by Professor Marilyn Vihman.
"We have tested about 20 babies since the beginning of the year, but we need 30 children in four age groups - nine, 10, 11 and 12 months," she said.
"We want children from English, Welsh and bilingual families.
"Research has led us to understand at what age infants learn to recognise familiar words," said Dr Guillame Thierry, who is in charge of the ERP project.
"Now we want to learn when recognition develops into understanding, and whether babies begin to pay more attention to words that they already understand or to new unfamiliar words."