For the study, published in Journal of Neuroscience, researchers from New York University’s Department of Psychology tracked the activity of a region of the brain, the amygdala, responsible for social and emotional behaviour. Previous studies have shown that this region of the brain is linked to the processing of facial cues, including how trustworthy an individual is.
The researchers conducted a pair of experiments to monitor the activity of subjects’ amygdala while they were exposed to a series of facial images. These images had been modified to enhance features like high inner eyebrows and well-defined cheekbones, known to signal trustworthiness, and the opposite to signal untrustworthiness. Another group of people were asked to evaluate the same faces on how trustworthy they found them, in order to ensure that the assumptions made by the previous group were correct.
During the experiment, when the brain activity of participants was being monitored, the participants had to view the images during a process called backward masking. This process, used in cognitive experiments, involves showing two images, or an image and another form of stimuli, in quick succession. This is done so as to mask the content of the images. In the current experiment, the faces were masked to ensure that while they were exposed to the facial images, the participants were actually not aware of the faces. The researchers found that although the participants could not see the face consciously, the brain exhibited activity that indicated it was tracking the general trustworthiness of it.
The authors write in the journal, ‘The findings demonstrate that the amygdala can be influenced by even high-level facial information before that information is consciously perceived, suggesting that the amygdala’s processing of social cues in the absence of awareness may be more extensive than previously described.’