Scientists believe they have worked out exactly how we recognise a face when we see it.
Preference for faces begins at birth
Experts have known for some time that there is something special about faces that draws us to look at them, even after the first few hours of birth.
A brain region called the fusiform face area (FFA) has been pinpointed as key.
Now a team at Massachusetts Institute of Technology say in the journal Neuron that they have figured out how the FFA processes this visual information.
To find out what was going on in the brain, the researchers asked volunteers to take part in an experiment.
The volunteers were asked to look at pictures of different faces and also pictures of an inanimate object - a house.
At the same time, the volunteers' brains were scanned using functional magnetic resonance imaging (fMRI), which shows up which areas of the brain are active at any given time.
Some of the faces that the volunteers looked at were completely normal, while others had features that were spaced differently or had features that were replaced by those of different faces, such as a different nose or mouth.
Drawn to faces
Similarly, the pictures of the houses were manipulated in the same way - differently spaced windows or different doors.
The top row of faces have different features. The bottom row vary in spacing of the features. Courtesy of Neuron and the study authors.
From these experiments, Galit Yovel and Nancy Kanwisher were able to confirm that it was the FFA that processed the visual information.
The FFA was not activated when the volunteers looked at the pictures of houses, suggesting that it is indeed specific for faces.
They also worked out that it was the face as a whole that was recognised, rather than the individual features or the relative spacing of these features.
This is contrary to what some researchers have believed in the past.
Dr Gunter Loffler, from the Glasgow Caledonian University, has conducted similar research and said: "It's a very nice study.
"There has been quite a bit of controversy over the FFA in the past.
"Some have suggested it is not face specific but related to expertise - when something is familiar because you have seen it over and over again.
"This study suggests it is just faces that activate this area.
"And it does not matter whether the position of the features differs or the features are swapped or substituted."
He recommended more studies to confirm this.
The findings could be particularly important for treating people with brain damage from things such as a stroke, or when operating on someone to manage their epilepsy, he said.
"Knowing there is an area in your brain and in my brain that is very important for face recognition is helpful.
"I'm not surprised that humans have developed a face specific area in the brain.
"Even babies a few hours after birth will look at their mother's face over other things.
"It's a very important skill for social interactions."
Dr Roberto Caldara, a visiting post-doctoral fellow at the University of Glasgow, said it was unlikely that one area of the brain would be involved in this process alone.
"Things are more complicated than that. It's more complex than just a single area."
For example, he said, one patient who had lost the ability to distinguish between different people by their faces, but could still tell when they were looking at a face as opposed to an inanimate object, had an intact FFA.
"So it's not clear cut," he said.