For every one percent increase in duplicated words, children learned an average of 2.72 extra words a month. Picture: Flickr.com

London - Some parents get so fed up with baby talk, they feel like they’re going ga-ga.

But linguists have discovered that calling the train a "choo-choo" – or the family pet a "doggie" – could give your child’s vocabulary a major boost.

Experts have discovered that families who most use two types of words have infants with better language skills. The key is to duplicate sounds – such as "tum-tum" or "din-dins" – or use simple two-syllable words ending in "y" or "ie" such as "horsie" or "fishy".

Dr Mitsuhiko Ota, who led the study of 47 infants at the University of Edinburgh, said: "At first glance baby talk words may appear to be unhelpful because extra words, such as 'bunny', as well as 'rabbit', are not needed by children when they grow up.

"But our study suggests that baby-talk words fit a pattern which attracts babies’ attention [and] allows them to understand which unit of speech is a word and commit it to memory. This is an important process."

The advantage of words like "doggie" and "teddy" is that, like many English words, they have one strong syllable followed by a weak one. Babies learn they are words because they have the same rhythm and end in the same sound.

Researchers looked at how often parents used the words in 90-minute recordings, along with duplicated and partially duplicated words such as "bow-wow". These results, taken when the babies were nine, 15 and 21 months, were then compared to how many words they could say and understand from a vocabulary list. 

For every one percent increase in duplicated words, children learned an average of 2.72 extra words a month.