You’ve heard it before: the characteristically exaggerated, sing-songy tone of voice parents adopt while speaking to their infant children. Interestingly, this infant-directed form of speech—usually characterized by the speaker’s use of high-pitched, slowly pronounced words—has been found to be used by language speakers from a diverse range of cultures around the world (Hilton et al. 2022). The seemingly global use of baby talk naturally raises the question: what function does it serve?
Over the past few decades, linguists and psychologists alike have proposed many theories attempting to explain why adults use infant-directed speech (IDS) when speaking to toddlers. One such theory, called the hyperarticulation hypothesis, suggests that the overly exaggerated enunciation of words, a defining characteristic of baby talk, directly promotes language acquisition. Another theory, known as the prosodic hypothesis, proposes that adults modify their speech to better convey their emotions and maintain the attention of their toddlers (Wong and Ng 2018).
So which theory more accurately describes what’s going on? As intuitive as the hyperarticulation hypothesis might seem, recent studies have actually reported findings that are inconsistent with it. For instance, in a study published in 2015, researchers used speech samples from Japanese-speaking mothers to test whether the contrast between phonemes (the smallest units of sound in linguistics) was more distinguishable in adult-directed speech (ADS) or IDS. Using speech technology software and an acoustics analysis algorithm, the team concluded that phonetic contrast was slightly—but still significantly—more pronounced in adult-directed speech than in baby talk, which does not support the hyperarticulation hypothesis of IDS’ purpose (Martin et al. 2015). The researchers also noted that their conclusions remained consistent with the prosodic hypothesis proposing that baby talk serves more of a “communicative function” to keep toddlers engaged (Martin et al. 2015). A separate study done three years later with Cantonese-speaking mother-child dyads reached a similar conclusion: the researchers, Wong and Ng, found that there was no significant difference in articulation between ADS and IDS. The team therefore concluded that their results seemed to support the prosodic hypothesis, where IDS is used as a form of “affectionate speech” to maintain the attention of children (Wong and Ng 2018). These studies seem to demonstrate that baby talk facilitates speech development on a cognitive level.
Still, it’s important to note that the prosodic hypothesis has not been definitively proven; further research is therefore required to better understand the function and impact of baby talk. There is little doubt, however, that future work in the field will help lead to exciting new breakthroughs in understanding how we acquire language.
Hilton, Courtney B., et al. “Acoustic Regularities in Infant-Directed Speech and Song across Cultures.” Nature Human Behaviour, vol. 6, 18 July 2022, pp. 1545–1556, www.nature.com/articles/s41562-022-01410-x, 10.1038/s41562-022-01410-x.
Martin, Andrew, et al. “Mothers Speak Less Clearly to Infants than to Adults: A Comprehensive Test of the Hyperarticulation Hypothesis.” Psychological Science, vol. 26, no. 3, 28 Jan. 2015, pp. 341–347, 10.1177/0956797614562453.
Wong, Puisan, and Kelly Wing Sum Ng. “Testing the Hyperarticulation and Prosodic - ProQuest.” Journal of Speech, Language, and Hearing Research, vol. 61, no. 8, 1 Aug. 2018, pp. 1–19, DOI:10.1044/2018_JSLHR-S-17-0375. Accessed 19 Jan. 2023.