Even when we are resting, our brains are preparing us to be social, according to a new study by psychologists from the University of California, Los Angeles.
The study sheds light on why social networks such as Facebook are such a popular diversion for people who feel like taking a break, researchers said.
"The brain has a major system that seems predisposed to get us ready to be social in our spare moments," said Matthew Lieberman, a UCLA professor of psychology and of psychiatry and biobehavioural sciences.
In experiments at UCLA's Ahmanson-Lovelace Brain Mapping Center, the researchers showed photos with captions to 21 people, and tracked their brain activity using functional magnetic resonance imaging, or fMRI.
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Most of the photos showed people performing actions in a social setting and expressing a certain emotion. In one set of 40 photographs, images were paired with captions that reflected the person's mental state.
A third set of images depicted a number accompanied by a simple mathematical equation.
Participants were asked to judge whether the captions accurately expressed what the images showed.
The same regions of the brain that were active during the brief times that subjects were not looking at photos were also active when the participants were considering the photos with captions about people's emotions.
But those areas of the brain were not active when the participants were viewing the cards with captions about the person's physical activity and those with the math equations.
In those cases, the participants made significantly faster judgments if the next photo they saw presented a statement about the person's mental state.
The findings suggest that the dorsomedial prefrontal cortex might turn on during dreams and rest in order to process our recent social experiences and update our assumptions and understanding of the social world, Lieberman said.
So although Facebook might not have been designed with the dorsomedial prefrontal cortex in mind, the social network is very much in sync with how our brains are wired, he said.