One Face, Many Places: The Development of Different Cortical Regions Responsible for Face Processing

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Saxe, R., & Kosakowski, H. L. (2025). Origins of face responses in the human cortex: fNIRS and fMRI evidence from infants. Current Directions in Psychological Science.

When we look at someone’s face, we take in a remarkable amount of information—often without even realizing it. A face can seem familiar or new, attractive or off-putting, still or in motion. We sense emotion, make judgments about personality or intent, and decide—almost instantly—if someone seems friendly or threatening. These impressions arise from a rich blend of visual, emotional, and social cues, and the brain handles this complex task by engaging multiple regions simultaneously, each processing a different aspect of the face. 

In adults, three key areas of the brain are known to respond specifically to faces. These include the fusiform face area (FFA), the superior temporal sulcus (STS), and the medial prefrontal cortex (MPFC). 

Each of these plays a unique role in how we perceive and understand faces. New research by APS Fellow Rebecca Saxe and Heather Kosakowski (2025) explores how these areas develop in infancy, offering exciting insights into the early development of social perception.

The brain’s face network

• Fusiform face area (FFA)
  Perhaps the most well-known of the three, the FFA becomes more active any time we see a face—whether it’s familiar or new, in motion or still, in color or silhouette. When this region is stimulated in adults, people may even hallucinate that they are seeing a face where none exists. The FFA appears to help us recognize identity, enabling us to know who someone is regardless of how they’re feeling or the angle from which we see them.
• Superior temporal sulcus (STS)
  This area of the brain, which runs along the side of the temporal lobe, is especially active when we see faces in motion or hear human voices. It seems to help us interpret others’ thoughts and feelings in real time—what someone might be feeling, thinking, or intending in the moment.
• Medial prefrontal cortex (MPFC)
  Situated at the front of the brain, where the left and right hemispheres meet, the MPFC is involved in processing situations that carry personal or social meaning—like when someone makes direct eye contact, calls your name, or is someone you know. It’s also active when we hear familiar voices or listen to stories about people we care about.

Together, these areas allow us to move from simply seeing a face to understanding it in a deeply human, emotionally rich way.

How do these brain areas develop in infants?

One possibility is that these areas develop gradually, beginning with those involved in basic visual processing (like the FFA) and maturing later into areas involved in more complex social understanding (like the MPFC). This kind of “posterior-to-anterior” development pattern has been seen in other parts of the brain and aligns with how white matter connections (myelinated axons) mature over time (Bethlehem et al., 2022).

If this were the case, we’d expect young infants to respond mostly to visual aspects of faces (e.g., recognizing a face is present), with more nuanced social processing coming later. However, new evidence suggests something more surprising—and hopeful: that even very young infants may already be tuned in to the social and emotional aspects of faces.

What the latest research shows

Studies using brain imaging methods like fNIRS (near-infrared spectroscopy) and fMRI have found that infants as young as 4 to 6 months show activity not only in the FFA but also in the STS and MPFC. For instance:

• Six-month-olds show stronger STS and MPFC responses when watching two people interact, compared to watching them act alone (Farris et al., 2022).
• Four-month-olds show more activity in these same regions when a face looks directly at them, versus when it looks away (Grossmann et al., 2008).

More recent fMRI studies by Kosakowski and colleagues (2022, 2024) show that even 2-month-old infants respond selectively to faces across all three brain areas—FFA, STS, and MPFC. Interestingly, the pattern of brain activation in 2-month-olds looks very similar to that in 9-month-olds. This suggests that these regions may not develop in a simple sequence but rather in parallel, supporting infants’ early ability to interpret both the look of a face and its social meaning.

Conclusion

Faces are among the most important stimuli we encounter as humans, and our brains are exquisitely tuned to perceive and interpret them. The latest research shows that even young infants are surprisingly socially aware, with brain systems that may be ready to process the meaning behind a face from the very beginning. Understanding how these systems develop opens a window into the origins of human connection—and raises fascinating questions about how our minds grow from the earliest days of life.