Shortly after receiving a cochlear implant, infants develop vocalization patterns similar to those of their hearing peers. (Source: Bjorn Knetsch, Wikimedia Commons)
Infants typically engage in repetitive babbling of consonants and vowels, such as “ba-ba,” at seven or eight months of age. However, infants with profound hearing loss do not typically vocalize such sounds until they receive cochlear implants. According to Mary Fagan, an assistant professor at the University of Missouri, infants’ ability to hear themselves motivates them to produce these repetitive babbles (1).
To investigate the motivation behind infants’ repetitive babbling, Fagan studied 27 hearing infants and 16 infants with profound hearing loss (1). Fagan collected data at two time points. At the first time point, before those with hearing loss received cochlear implants, infants were on average 9.9 months old; at the second time point, about four months after infants with hearing loss had their cochlear implants activated, infants were on average 17.7 months old. All of the parents of the infants in the study could hear and primarily spoke with their infants in English.
Infants were recorded while playing with 24 objects and then while playing with their parents. Fagan then measured the number of vowel-only sounds, consonant-only sounds, and consonant-vowel sounds (such as “ba”).
Interestingly, pre-cochlear implant infants had a unique pattern of vocalizations; they produced mainly vowel sounds and rarely produced repetitive consonant-vowel babbles (1). After receiving a cochlear implant, they began to produce more consonant-vowel sounds, and their vocalization patterns were more similar to those of younger hearing infants. Both the 17.7-month-old infants with cochlear implants and the 9.9-month-old hearing infants produced similar numbers of vowel-sounds and consonant-vowel sounds (1).
By 17.7 months, the hearing infants produced many more consonant-vowel sounds than vowel sounds (1). However, there was not a significant difference in the number and length of consonant-vowel repetitive babbles produced by post-cochlear implant infants and hearing infants at 17.7 months (1). In short, the post-cochlear implant infants had begun to produce longer strings of repetitive babbles, such as “ba-ba-ba-ba” (2).
Fagan concludes that the speed at which infants began to engage in repetitive babbling after they received cochlear implants, despite how uncommon syllable repetition is in English words, suggests there is a purpose behind infants’ repetitive babbling (1). Producing these repetitive babbles and listening to the resulting sounds may help infants form and strengthen cortical areas of the brain involved in producing and perceiving speech (1).
References:
- Fagan, Mary K. Why repetition? Repetitive babbling, auditory feedback, and cochlear implantation. Journal of Experimental Child Psychology, 2015; 137: 125-136. http://dx.doi.org/10.1016/j.jecp.2015.04.005
- University of Missouri. (2015, October 22). Babies’ babbles reflect their own involvement in language development: Infants are motivated by hearing themselves. ScienceDaily. Retrieved from www.sciencedaily.com/releases/2015/10/151022125740.htm