Foetuses learn, memorise words

Can babies learn while still in the womb of their mother? It has been long believed more as folklore that they can and do. It is with this belief that mothers-to-be and family members sing lullabies and soft songs to the baby even before birth. Some support for this long-held belief comes from a recent study by a Finnish group published in the September 10 issue of PNAS (U.S.). Titled “Learning-induced neural plasticity of speech processing before birth”, it suggests that as a child in the foetus is exposed to speech, its brain responds, records and remembers some words.

How does one do such experiments and arrive at solid conclusions? First of all, note that during the foetal period, the growing baby’s brain develops progressively and extensively. As the brain develops, new neuronal connections called synapses are made. This helps in efficiently recognising, analysing and recording complex information. In other words, the baby is growing not just in the body but in the brain as well.

Of the five senses — sight, touch, smell, taste and sound — it is sound that comes largely from outside the womb. Smells from outside cannot reach the womb since the smell molecules cannot easily cross and enter the womb and the foetus’ nose. The eye is still developing and in any event, the foetus is confined within the dark and crowded space. Touch perhaps — if the pregnant mother or others caress the bulky stomach, the developing baby within it almost certainly feels it and is perhaps comforted, while a jolt can be quite disturbing and even dangerous. And even if the baby were to utter sounds, the experimenter sitting outside can record it more as a series of vibrations in the womb and to make sense out of it could be a problem. But one could produce sound from outside and check whether the baby in the womb registers it. Thus the sense of hearing of the foetus is open to experimentation. The way the Finnish group did it was to recruit 17 expectant mothers. And five to seven times a week, they were exposed to the simple three syllable sound “ta-ta-ta” (each time for about 4 minutes) sufficiently loudly so that the sound would pass the intra uterine walls. The foetus could “hear” (not too loud as to be threatening).

They then did the same experiment five days after their birth. The same “ta-ta-ta” was played, but once in awhile the tune was deliberately changed to “ta-TA-ta” so that the pitch changed (and other similar mismatch sounds). Electrodes were stuck to the babies’ skulls to monitor their electroencephalograms (EEG). Whenever the pre birth “ta-ta-ta” was heard, the EEG recording showed the babies to register the sound of the word but when the mismatch word “ta-TA-ta” was played, the babies responded right away, revealing that something was wrong (as if “hey, this is outside my known vocabulary”!). In contrast, 16 “control” babies who had not heard these pre-birth “ta-ta-ta” recordings did not show any such mismatch response when they heard the “ta-TA-ta” mismatch sounds.

These results suggest that babies could learn syllables and remember words they had heard before birth, while in the womb of their mothers. Since the onset of hearing in human infants is around the 27 week of gestation, it would seem that any words or sounds they are exposed to earlier than this period might not be registered. Also note that the researchers used low pitch sounds and not high pitch. Low pitch sound travels and crosses materials better: elephants in woodlands and whales in oceans communicate among themselves using low pitch sources.

One question is how long would these pre-birth memories last. Experiments towards this would be of interest. And another is whether such in-the-womb training can help children with potential problems of language acquisition or dyslexia. The Finnish group believes that words or songs played during pregnancy might prove helpful. Lastly, erudite readers will already have thought of Greek mythology or of the example of Abhimanyu in Mahabharata who, while in the womb, heard his uncle Lord Krishna explain to his mother Subhadra the details of the chakavyuha strategy of Dronacharya, and how to enter it. Even before Krishna could finish telling her how one gets out of the chakravyuha she fell asleep and Abhimanyu could not register this vital piece. And the result, sixteen years later, for Abhimanyu was disastrous. Well, I need to ask this question in this context — does the pre-birth memory of words last 16 years?

In the reference to five senses, the fifth sense taste was left out. It has been added now.

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Printable version | Jan 16, 2022 9:52:57 PM | https://www.thehindu.com/sci-tech/science/foetuses-learn-memorise-words/article5240316.ece

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