The relationship between timing of single-syllable utterances and breath support in infants during the second year of life

Abstract

The critical window for language development is in the first three years of life. Throughout the second year, speech development is more rapid than at any other stage. The second year of life is marked by the emergence of increasingly complex utterances and vocabulary growth. Infants at this stage have growing demands on their respiratory system. This study explored the relationship between the timing of expiration and the timing of utterance production in infants in the second year of life. Single-syllable utterances of six healthy infants (17 to 25 months) were identified along with the expiratory phases underlying them. The coders then measured and tabulated (a) the lag between the start of expiration and the start of each single-syllable utterance, and (b) the lag between the end of the utterance and the end of expiration. The collected data was plotted on scatterplots with the lag between the expiratory phase start and the utterance start on a y-axis, and the lag between the utterance end and the expiratory phase end on the x-axis and examined for patterns. Visualization of these infants' data suggested some patterns in respiratory timing for single-syllable utterances. There was some individual variation among the infants, but in general the older infants demonstrated more flexibility in the timing of respiration to support speech production. More research is needed to help explain how typically developing infants learn to produce speech, as well as identify possible physiological markers for increased language complexity in later infancy.