The stereotypes we hold shape the way our brain perceives other people's faces, scientists say. They alter the brain's visual representation of those around us, distorting what we see to be more in line with our bias.
The study, published in the journal Nature Neuroscience, follows up on previous research, which concluded that stereotypes are key to the understanding of how we behave in society, and that they changed the nature of our interactions with others.
Here, the scientists wanted to investigate the cognitive processes involved in stereotyping. They found out that bias impacts the functioning of the brain's visual system, prompting us to see people in a way that confirms our stereotyped judgements.
Hand movements and stereotypes
The scientists monitored the brain activity of participants using functional magnetic resonance imaging (fMRI), while they looked at different faces of people from different genders and ethnic origins, and displaying different emotions. After the brain scanner, the researchers used an innovative mouse-tracking technique to record people's hand movements as they used a computer to categorise the faces they had just seen according to sex, skin colour and emotions.
An analysis of these hand movements revealed unconscious cognitive processes and stereotypes individuals held. Their concious responses indicated a good recognition of the faces, but hand movements suggested a number of profound, unconscious biases.
Men - black men in particular - tended to be seen as "angry", while "women" were perceived as "happy", even though they didn't objectively show signs of these emotions. These findings suggest unconscious stereotypes impact the way our visual system processes peoples' faces, leading us to see them in a way that confirms our prejudices.
"Many individuals have ingrained stereotypes that associate men as being more aggressive, women as being more appeasing, or black individuals as being more hostile, though they may not endorse these stereotypes personally," lead author Jonathan Freeman explains. "Our results suggest that these sorts of stereotypical associations can shape the basic visual processing of other people, predictably warping how the brain 'sees' a person's face."
Impact on the brain
Evidence of visual stereotyping can be directly observed on fMRI scans, in particular in a region of the brain involved in the visual processing of faces called the fusiform cortex.
For example, when participants looked at at white female faces, neural-activation patterns that appeared in the fusiform cortex were similar to those elicited by objectively happy faces. The extent of this stereotypical similarity in neural-activation patterns was correlated with the extent of bias observed in a subject's hand movements.
"The findings highlight the need to address these biases at the visual level as well, which may be more entrenched and require specific forms of intervention. This visual bias occurs the moment we glimpse at another person, well before we have a chance to correct ourselves or regulate our behaviour", Freeman concludes.