Babies find it easier to learn words with repetitive syllables rather than mixed sounds, academics have found.

Edinburgh University researchers assessed language learning in 18-month-olds for the study.

They found children were better at grasping the names of objects with repeated syllables over words with non-identical syllables.

The findings may help to explain why some words or phrases, such as "train" and "good night", have given rise to versions with repeated syllables, such as "choo-choo" and "night-night".

Because the words are easier for infants to learn, they may provide them with a starter point for vocabulary learning, the team said.

Academics assessed the infants' language learning behaviour in a series of visual and attention tests using pictures on a computer screen of two unfamiliar objects.

The two objects were named with made-up words which were communicated to the infants by a recorded voice - one with two identical syllables, for example, "neenee" and the other without repeated syllables, such as "bolay".

The toddlers were then tested for their recognition of each made-up word.

Recordings of their eye movements showed they looked more reliably at the object labelled with repeated syllables than the other object.

The results were validated with a control test in which the infants responded to pictures of familiar objects - such as a dog or an apple.

Previous studies show that infants more easily learn patterns involving repetition in visual sequences and musical notes.

Academics said their latest findings suggested that this tendency extended to learning words.

Lead researcher Mitsuhiko Ota, of Edinburgh University's school of philosophy, psychology and language sciences, said: "This is the first evidence to show that infants have a strong bias in learning new words.

"It also shows that there may be a good reason why in so many cultures across the world, existing adult words and expressions are replaced by words with repeated syllables in baby-talk vocabulary.

"Some examples could be tum-tum, mama, dada, din-din and wee-wee."