Word-initial voicing in the productions of stops in normal and preterm infants

It has been traditionally held that developmental anomalies in language acquisition are more frequent in neonatologically at-risk subjects. There is some suggestion that proficiency in phonology is correlated with the motor control development. The purpose of this paper was to compare the patterns of acquisition of the control of the acoustic-phonetic cues for voicing in the speech of premature infants and controls. The measure studied was initial stop consonant Voice Onset Time (VOT), which is known to be the most reliable acoustic cue for the distinction between voiced and voiceless stops.
The total population of the study consisted of 7 infants born at less than 37 weeks gestation. A control group of 7 infants born full-term at normal weight and 7 adults, aged from 24 to 26 years, also partecipated. Each child was recorded under standard recording conditions saying words contrasting labial, dental and velar voiced and voiceless initial stops. Elicited word productions were collected monthly from infants, at different age levels, ranging from 18 to 21 months.
The results show that our subjects are more advanced in the acquisition of the appropriate VOT values for the voiceless than for the voiced consonants.This difficulty may be related to the increased neuromuscular control and more complex muscle activity necessary for mantaining voicing during the closure, especially for velar stop. It is important to recognize the possibility that increased variability in preterm children may be related to some neuromuscular immaturity