A study revealed the biological underpinnings of our social responses. Neuroscientists at UCLA’s Ahmanson-Lovelace Brain Mapping Center used functional MRI scans to measure brain activity in volunteers while they viewed photos of people expressing emotions in social settings.

The volunteers were asked whether the photo captions accurately described the images. Some of the photos had captions that described the person’s mental state — such as angry or sad.

Other captions designated the action in the photo, such as sitting or standing; others simply provided a math equation such as 1 + 1 = 2.

The scientists found that a particular brain region — the dorsomedial prefrontal cortex — fired up while the volunteers viewed photos with captions describing a person’s emotions, but not while viewing photos with the other types of captions.

The volunteers made faster judgments when a photo was paired with a caption about mental state.

The dorsomedial prefrontal cortex also charged up when volunteers anticipated viewing photos, suggesting that our brains prepare for future interactions.