Your brain makes a spontaneous judgment of whether or not another person’s face is trustworthy before you are even conscious of it, according to new research published in the Journal of Neuroscience.
“Our findings suggest that the brain automatically responds to a face’s trustworthiness before it is even consciously perceived,” said study author Jonathan Freeman, Ph.D., an assistant professor in New York University’s Department of Psychology.
“The results are consistent with an extensive body of research suggesting that we form spontaneous judgments of other people that can be largely outside awareness,” added Freeman, who conducted the study as a faculty member at Dartmouth College.
The study focused on the amygdala, a part of the brain important for humans’ social and emotional behavior that has been shown in past studies to actively judge the trustworthiness of faces. It was not known, however, whether the amygdala was capable of responding to a complex social signal like a face’s trustworthiness without that signal reaching conscious awareness.
To find out, the researchers conducted a pair of experiments in which they monitored the activity of participants’ amygdala while the participants were exposed to a series of facial images.
These images included photographs of actual strangers’ faces as well as artificially generated faces whose trustworthiness cues could be manipulated while all other facial cues were controlled.
The artificially generated faces were computer-synthesized based on previous research showing that cues such as higher inner eyebrows and pronounced cheekbones are seen as trustworthy and lower inner eyebrows and shallower cheekbones are seen as untrustworthy.
Before the study, a separate group of subjects examined all the real and computer-generated faces and rated how trustworthy or untrustworthy they appeared. As expected, subjects strongly agreed on the level of trustworthiness shown by each given face.
During the study, a new set of participants viewed these same faces inside a brain scanner, but were exposed to the faces very briefly, for only a matter of milliseconds.
This quick exposure, along with another feature known as “backward masking,” prevented participants from consciously seeing the faces. In backward masking, subjects are presented with an irrelevant “mask” image that immediately follows an extremely brief exposure to a face, which is thought to terminate the brain’s ability to further process the face and prevent it from reaching awareness.
The researchers found that specific regions inside the amygdala exhibited activity tracking how untrustworthy a face appeared, and other regions inside the amygdala exhibited activity tracking the overall strength of the trustworthiness signal. This even though participants could not consciously see any of the faces.
“These findings provide evidence that the amygdala’s processing of social cues in the absence of awareness may be more extensive than previously understood,” said Freeman. “The amygdala is able to assess how trustworthy another person’s face appears without it being consciously perceived.”
Source: New York University