Study finds baby's first sounds directly linked to changes in heart rate

New Delhi: A baby's first sounds and attempts to form words could be signs that their heart is working in sync with developing speech, according to a study that found that they were directly linked to each other.

Researchers from the University of Houston, US, explained that for infants, producing recognisable speech is more than a cognitive process -- it is a motor skill requiring a coordination of many muscles performing varied functions throughout their body.

This coordination is directly linked to fluctuations in heart rate, they said.

"Thus, for the developing infant, heart rate fluctuations align with the timing of vocal productions, and are associated with their duration and the likelihood of producing recognisable speech," the authors wrote in the study published in the journal Proceedings of the National Academy of Sciences.

The findings are important for understanding how language develops and potential early indicators of speech and communication disorders, they said.

For the study, the researchers analysed over 2,700 sounds of varying dynamics -- such as a laugh, babble or a coo -- made by 34 infants, aged 18-27 months old and who did not speak whole words yet.

The team found that changes in heart rate were in line with the timing and duration of sounds.

"Heart rate naturally fluctuates in all mammals, steadily increasing then decreasing in a rhythmic pattern. It turns out infants were most likely to make a vocalisation when their heart rate fluctuation had reached a local peak (maximum) or local trough (minimum)," author Jeremy I. Borjon, an assistant professor of psychology at the University of Houston, said.

"Vocalisations produced at the peak were longer than expected by chance. Vocalisations produced just before the trough -- when the heart rate is decelerating -- were more likely to be recognised as a word by naïve listeners," Borjon. About 10 per cent of the sounds analysed were found to be reliably identified as words by naive listeners.

The researchers explained that the first few years of one's life are marked by significant changes in how the heart and lungs function -- known to be controlled by the autonomic nervous system.

"The relationship between recognisable vocalisations and decelerating heart rate may imply that the successful development of speech partially depends on infants experiencing predictable ranges of autonomic activity through development," Borjon said. PTI KRS NB NB