From the time they are fetuses, babies can hear their mother’s voice. Research has shown that they recognize her voice shortly after birth and prefer her to the sound of other female voices.
In a previous study, deRegnier and colleagues (2000) presented newborns with a maternal and stranger’s voice while the infants slept. They found that ERP components, P2 and negative slow wave (NSW), differed between the two conditions.
Prenatal Exposure
Research over the last few decades has established that a baby’s response to the mother’s voice begins even before birth, with evidence of prenatal learning that carries into early postnatal life. Studies that elicit a reaction from the fetus to various sounds have shown that, in general, external sound stimuli like voices make a fetus move more and increase their heart rate, but when they hear their mother’s voice it calms them down, as indicated by a slower pulse rate, lower mobility and increased stability of behavior.
Using a technique called functional magnetic resonance imaging, or fMRI, researchers have demonstrated that when the maternal voice is played to the fetus a few days before delivery, there is a distinct activation of the left temporal cortex of the brain compared with other sounds. This suggests that your infant is already recognizing and responding to the sound of her mother’s voice.
Newborns respond almost unerringly to their own mother’s tape-recorded voice and are able to distinguish it from the voices of other women. Moreover, they will modify their behavior in order to activate their mother’s voice. For example, when a female stranger’s voice is played, the fetus will reduce their sucking on a pacifier in order to stimulate it. When their own mother’s voice is played, they will increase their sucking on the pacifier.
Ear Development
During the final trimester of pregnancy, a baby’s ears and brain mature enough to begin hearing sounds outside the womb. At first, babies hear mostly low-pitched sounds and can identify male voices more clearly than female ones. But as the ears and brain continue to develop, they can pick up higher-pitched sounds, including their mother’s voice.
A number of studies confirm that newborns prefer their mother’s voice over other female voices, and even respond to her by adjusting their behavior. In addition, fMRI research shows that the maternal voice activates brain regions involved in speech processing, while other women’s voices stimulate only the insula and frontal cortex.
In one study, researchers presented 2-day-olds with a series of audio recordings. They heard the recorded cries of different infants and had to determine whether the cries belonged to the mother or to a stranger. The participants listened for 10 min, and then were asked to repeat the test after a 10-min interval. This second test was used to measure the babies’ memory of their assigned cries.
The results of the retest showed that the babies remembered the cries of their own mothers and didn’t recall the cries of other infants as well as they remembered their own mothers. Moreover, the pitch height of the mother’s voice was found to be associated with the children’s perception of the emotional intensity of their mothers’ vocalizations (Stoop et al 2020). In other words, the higher the pitch of the mother’s voice, the more the children perceived her emotions as intense.
Mother’s Voice
The mother’s voice is a highly salient social stimulus from the very beginning of life. Even in utero, a fetus can recognize her mother’s voice and will work to hear it better than an unfamiliar female voice2.
When infants are born, they continue to prefer their mothers’ voices. In one classic study, 1-day-old babies sucked harder on their pacifier when hearing their mother’s tape-recorded voice than another woman’s. This shows that a child’s innate desire to connect with their mother is strong from the very start of their lives3.
In terms of specific acoustics, researchers have found that children prefer their mother’s voice based on the pitch of her voice. The higher the pitch of the mother’s voice, the more the child prefers it (van Rooijen et al 2020).
In fact, it has been shown that a mother’s voice activates areas of her infant’s brain more strongly than an unfamiliar female voice does, priming the baby for the specialised task of speech processing4. In school-aged children, hearing their mother’s voice evokes activity in a number of brain regions associated with salience, reward, facial recognition, and social functioning5. This is likely because the emotional context of a parent’s voice is a powerful predictor of the way that the child will develop their own ability to connect and communicate with others5.
Social Environment
As a result of their prenatal exposure to speech, newborns are capable of making some remarkable distinctions. One of the most impressive is that they can recognize their mothers’ voices within days (and sometimes hours) of birth. This is important because infants need to be able to differentiate between the mother’s voice and other female voices in order to develop social communication abilities.
As researchers have investigated the power of the mother’s voice, they have found that it triggers activity in specific brain regions. In particular, the amygdala, which regulates emotions, the nucleus accumbens, which is involved in reward circuitry, and the fusiform face area, which processes visual face information are activated by the mother’s voice. This pattern of brain activation is similar to a fingerprint and is referred to as the “neural fingerprint.”
Interestingly, it has also been reported that infants prefer their own mother’s voice over other women’s voices. One explanation for this is that a mother’s voice is more likely to contain the oxytocin chemical, which promotes social bonding and relaxation.
As a way of testing this, scientists placed newborns in an MRI machine and played them recordings of a woman’s voice. The results showed that newborns listened for their own mother’s voice and responded by opening their mouth more often than they did when listening to other women’s voices.
