Infants may pick up on people's faces before anything else, which could explain why they can be scared of strangers at a young age.
Babies may be able to identify people’s faces before anything else, such as cars or letters of the alphabet. Researchers have found that infants as young as 4 months old produce a distinct brain signal when they see an image of someone’s face, which could explain why some babies become scared of strangers at around this age.
 |
| Babies produce a brain signal that suggests they can identify faces at 4 months old, with this signal becoming more robust from 6 months d3sign/Getty Images |
Kalanit Grill-Spector at Stanford University in California and her colleagues wanted to better understand how infants interpret the world around them. To do so, they studied the brain activity of 45 children, who were between 3 and 15 months old, while they looked at a series of rapidly appearing images: strangers’ faces, corridors, cars, letters and human limbs. The team chose these images, which were all grey, as they are regularly present in most children’s lives, says Grill-Spector.
The children were shown the images on a screen for 1 minute at a time. The researchers repeated the 1-minute experiment six to 12 times per child while they wore an electroencephalogram headset to measure their brain activity.
The team found that the images of faces elicited a distinguishable brain signal in the participants from just 4 months old. This became more robust in the children who were between 6 and 8 months old, the same age that corridors and limbs started to elicit a similar signal. Letters generated such a signal at 12 to 15 months, but none of the children produced a distinct brain signal when looking at cars.
Producing these brain signals suggests that each child is identifying the category of object that the image belongs to, says Grill-Spector. “So for faces, we’re saying the infants can appreciate that they’re all similar in some ways and belong to the same category of objects,” she says. “They can tell these apart from other objects like limbs and cars.”
The results are in line with previous research that suggests that babies become afraid of strangers at around 8 months old, says Grill-Spector. “It might take time for babies’ retinas to mature to a level where you can really tell people apart from their faces.”
Babies may also recognise faces relatively early on in their lives because these are what they spend most of their time looking at, says Grill-Spector. “It’s only when a child is around 1 year old that they’re mobile and dexterous and they’re interacting with a lot of objects,” she says.
Measuring how seeing different objects relates to brain activity could one day help diagnose children with autism, says Grill-Spector. People with autism can have some differences in their facial perception, she says. “Analysing this brain signal could be a way to detect autism in a pre-verbal infant.” Further research into this is required, she says.
“This study addresses the fundamental question of how infants structure and make sense of the barrage of information from their novel and complex visual world,” says Anna Franklin at the University of Sussex, UK. “The methodological innovations of the study pave the way for identifying when the infant brain selectively represents many other types of visual categories, such as food.”
Reference: