Why: A nap gives the brain time to give meanings to words
Your baby's first words are a critical milestone in their development - and parents focus on encouraging them with 'baby talk'.
But now researchers have shown the importance of sleep when it comes to an infant learning to talk.
In particular, sleep helps the important process of associating meanings to words - and not just perceive them as random noise.
That's according to scientists at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany.
They found that babies as young as six to eight months old were capable of the association - which until now was thought to happen later on.
And this occurred as a direct result of them being put down for a midday nap, the researchers say.
'Our results demonstrate that children hold real word meanings in their long-term memory much earlier than assumed, ' said senior author Angela Friederici.
'Although the brain structures relevant for this type of memory are not fully matured, they can already be used to a distinguishable extent.'
How the research was carried out
Scientists introduced six- to eight-month-old infants to 'fantasy objects' which they gave fantasy names such as 'Bofel' or 'Zuser.'
This was to make sure that the babies could not access any existing knowledge.
Objects that were the same type but differed only in form or colour were called the same names.
From the infants' reaction it was clear that they could not connect new objects of the same type with the corresponding name.
That means they did not recognise a new Bofel as a 'Bofel' although it was quite similar to the previously seen 'Bofel' versions.
Essentially, every new object-word pair was unknown and unique, the babies were unable to build a general relation between them.
However, their performance improved after a midday nap. In babies who fell asleep after the learning activity, the brain could differentiate between the right and wrong term for a new object.
The team say this shows they had consolidated their knowledge while they were sleep.
Babies that stayed awake could not manage to do so.
The duration of sleep had an influence too. A half-hour nap was not enough to see results, but those who slept for 50 minutes showed an improved reaction.
The researchers say memory is processed during sleep that also happen in typical lexical development of protowords.
These are words that are similar to - but not quite - actual words, such as 'gaga' for Grandma or 'baba' for bottle. This is said to usually happen between 10-12 months of age.
The team believe the duration of one stage of sleep could be of particular importance to 'lexical memory': the second of the four distinct phases.
'In our study, the babies received such a lot of information which they normally pick up within a longer time period,' says study leader Manuela Friedrich.
'But only during sleep, when the child's brain is disconnected from the outer world, can it filter and save essential relations.
'Only during the interaction between awake exploration and ordering processes while sleeping can early cognitive and linguistic capabilities develop properly.'
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