A groundbreaking study has found that twins often start talking later than single-born children - and that language delay is more common in identical twins than fraternal pairs.
The research project, which began in 2002, is an international collaboration between the Telethon Kids Institute, University of Kansas and the University of Nebraska Medical Center.
The findings were based on a sample of 473 sets of WA twins who were followed from birth.
Results from the LOOKING at Language study, recently published online in the Journal of Speech, Language and Hearing Research, also found that language delay was also found to be more common in identical twins than their non-identical counterparts.
Principal investigator UWA Professor Cate Taylor said, “Overall, twins have double the rate of late language emergence than single-born children; 38 per cent for twins, compared to 19 per cent for single-borns.”
“When we looked further at the twins, and split them into identical or non-identical twin pairs, we found the rate of language delay in identical twins was 47 per cent compared to 31 per cent in non-identical twins.”
Late language emergence is when a child’s language is below age and gender expectations - that is, when they speak few words and do not join words together to form sentences.
In this study, 71 per cent of two-year-old twins were not combining words, compared to only 17 per cent of single-born children.
Professor Taylor said the findings challenged existing views on why twins may have language delay.
“For years, researchers have been fascinated by language development in twins with the main theory that mothers speak less to twins due to the double demands of caring for two children of the same age,” Professor Taylor said.
She said while this may be true to a certain extent, the difference between the rate in identical and non identical twins pointed to there being another factor at play.
Professor Taylor said the explanation lies in factors other than growing up as two. For example, twins in general are exposed to more pregnancy and birth complications than single-borns, and identical twins even more so than non-identical twins.
Professor Taylor said the differences seen between identical and non-identical twins could be attributed to pregnancy and birth factors.
A study of pregnancy and birth risks for late talking in twins is currently underway.
“The answer to the question, 'Do the twins catch-up?’ is ahead of us. We are currently investigating the twin’s language development in the preschool and school years,” Professor Taylor said.
“It is vital to know if and when late-talking twins catch up to their peers or whether the language differences persist through childhood and into adolescence.”
Dee and Jodie, a Perth couple who have 20-month-old fraternal twin boys, say their sons are not quite as far along with their speech as other toddlers the same age but aren't too worried.
“They have their own babble and communicate with each other, so they are delayed with it somewhat, but they still manage to get their message out to each other," she said.
She said her boys, Josh and Lucas, use gestures, grunts and others noises as part of their own sort of language.
Dee said while they were a little behind in terms of how many words they were able to say at their 18 month check-up, they were also born prematurely, which she said likely played some part in their development.
“We’re not too concerned at the moment. The nurse said to wait a few months and if we need we can get them speech therapy," she said.
“All kids develop at their own rate."
Dee said while having twins is “definitely full-on” it is also “very rewarding and amazing watching them play and interact together”.