Infants are very adept at recognizing familiar voices and learning new ones. Studies suggest newborn babies already know their mothers’ voices and can distinguish between unfamiliar female voices within five months. However, their ability to recognize unfamiliar male voices has been a neglected research topic.

Yu et al. used a visual fixation procedure to gauge the responses of 48 infants, each 4.5 months old, to two male voices. They conducted a similar study in 2019, observing infants at this age could reliably discern unfamiliar female voices.

“We can't ask four-and-a-half-month-olds to make verbal responses or complete computer tasks,” said author Madeleine Yu. “We must infer their abilities from behavior alone.”

The subjects sat before a screen that displayed visual stimuli while recordings of a male speaker played repeatedly until the infants “habituated,” as demonstrated by their diminishing interest. Recordings of a second male speaker were then played. If the children detected a difference in speaker, their “looking behavior” would likely change, as was seen with female voices.

“We found no evidence they can tell apart unfamiliar male voices,” said Yu. “This is striking given the infants were drawn from the same population and tested by the same experimenters in an identical task.”

The researchers speculate young infants have increased sensitivity to female voices and suspect their home environments play a major role. Of 46 families who responded, all reported that their infant had a female primary caregiver.

“For years, research with infants used female voices under the assumption that results would be the same with male voices,” said Yu. “Our study contradicts this, and shows we must carefully consider how future research with infants is done.”

Source: “Learning to identify talkers: Do 4.5-month-old infants distinguish between unfamiliar males?” by Madeleine E. Yu, Natalie Fecher, and Elizabeth K. Johnson, JASA Express Letters (2024). The article can be accessed at https://doi.org/10.1121/10.0024271.