A recent study published in the Journal of Neuroscience caught my attention because it touches on a question that has fascinated me for more than four decades:
How can infants understand their mothers and caregivers long before they understand language?
This question has been with me since my undergraduate days at the University of Michigan. Like many important moments in life, my interest in this area emerged largely through circumstance and opportunity.
As a psychology student, I was invited to participate in the department’s honors program and challenged to design and conduct an original research study. When asked what interested me, I found myself returning to a simple observation: infants seem remarkably capable of understanding their mothers and caregivers despite not yet understanding words.
That question ultimately led me to conduct my first cross-cultural research project, examining preschoolers’ ability to recognize emotions from nonverbal vocal cues in the United States and Japan. It also led me to work with renowned psychologist Robert Zajonc at Michigan and, later, Paul Ekman in California. Looking back, that single question helped shape much of my career in the study of emotion and nonverbal communication.
Over the years, I have continued to follow research that sheds light on how emotional communication develops before language.
What We Know About Emotional Development Before Birth
Today, researchers have accumulated a substantial body of evidence showing that emotional and communicative systems begin developing remarkably early.
Studies using ultrasound and MRI technology have documented facial movements in fetuses beginning in the first trimester.
Around seven to nine weeks of gestation, simple facial movements such as mouth opening and eyebrow movements begin to appear.
By eleven to fourteen weeks, researchers can observe actions such as sucking, yawning, and grimacing. As gestation progresses, these movements become increasingly coordinated and complex.
Researchers have observed:
- Sucking and swallowing motions
- Mouth opening and closing
- Lip pursing
- Eye movements
- Grimace-like contractions
- Yawning
- Cry-like facial configurations
- Cheek and tongue movements
Of course, we must be careful when interpreting these movements. Many fetal facial actions may reflect neural and motor development rather than emotional experiences as we understand them in adults. Nonetheless, the evidence suggests that the biological foundations for emotional communication are developing well before birth.
What We Know About Infants After Birth
Research on infants provides additional evidence that emotional perception emerges early in life.
Numerous studies have shown that infants display increasingly differentiated emotional expressions during their first years. Other research indicates that infants as young as seven months old can distinguish between different emotional facial expressions, such as happiness and sadness.
Because infants cannot tell us what they perceive, researchers often rely on measures such as brain activity and attention patterns. These studies consistently demonstrate that infants are sensitive to emotional information long before they acquire language.
A New Study on Maternal Voice Recognition
Against this backdrop, I was particularly interested in a study published in the Journal of Neuroscience in December 2025 titled “The Neurotracking of the Maternal Voice in the Infant Brain“.
The study investigated whether infants track their mother’s voice differently from the voice of a stranger.
Twenty-five infants participated in the research. Before testing, each infant’s mother recorded herself reading a story. During the experiment, infants listened either to their own mother’s narration or to the narration of another mother while researchers recorded their brain activity using electroencephalography (EEG).
The findings were striking.
The infants’ brains showed clear evidence of tracking both familiar and unfamiliar voices. However, neural tracking was consistently stronger when infants listened to their own mother’s voice.
Importantly, this effect remained even though the acoustic properties of the stories were comparable. In other words, the infants were not simply responding to differences in sound patterns; they appeared to be responding specifically to the familiarity of their mother’s voice.
Building a Mountain of Evidence
This study adds to a growing body of evidence suggesting that infants come into the world already attuned to their mothers and other close caregivers.
My interpretation of this research is that we are slowly building a mountain of evidence that begins before birth and continues through infancy.
From fetal facial movements to infant emotion recognition to neural responses to maternal voices, the findings increasingly point toward the same conclusion: human beings appear biologically prepared to connect with the people who care for them.
The mechanisms underlying that connection are still being explored, and many questions remain unanswered. But studies like this bring us closer to understanding how infants can recognize, respond to, and learn from their caregivers long before they understand language.
More than forty years after I first became interested in this question, it is exciting to see science continuing to provide new pieces of the puzzle.
The post How the Infant Brain Tracks Their Mother’s Voice first appeared on Humintell | Master the Art of Reading Body Language.
Scientists have long understood that the human brain contains specialized systems dedicated to recognizing faces. 
One of the most significant implications of this research is that facial expressions appear fundamentally social.
Importantly, these findings should not be interpreted as evidence that facial expressions of emotion do not exist.
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