A study published in Neuroscience proposed that facial features associated with social dominance are rapidly and unconsciously processed in a perceiver’s brain.

This research was conducted by Su, Yaner, and Qu, Chen at South China Normal University, Tan, and Shaozhen at Guangzhou City Social Welfare Institute in Guangzhou, and Luo and Qiuling at Zhejiang Normal University in Jinhua, China.

Many societies tend to be socially organized into hierarchical structures. A key component within a social hierarchy is the transactional exchange between hierarchical levels, where dominant individuals (at the top) acquire benefits and submissive individuals (at the bottom) receive protection and care from a higher-rank individual. Social dominance hierarchies have been found to exist in many animal species, including primates, suggestive of an evolutionary element.

An individual’s ability to decipher the hierarchy of their group during social interactions is key for the establishment and maintenance of social alliances. Previous research has found that the ability to detect social dominance is present in infants as young as 10-months old. 

The purpose of this study was to examine if differences in social dominance can be detected and interpreted pre-consciously from perceiving a human face. The researchers aimed to bypass all conscious decision-making processes that occur when determining one’s social dominance by employing a technique called Fast Periodic Visual Stimulation (FPVS). This technique presents images very rapidly such that the individuals viewing them are not consciously aware of what they see.

It was hypothesized that more socially-dominant faces would be processed by the brain differently than less social-dominant faces which would suggest that high social dominance faces and low social dominance faces are recognized by the brain as two categorically distinct entities. 

Study and Findings Computer generated faces were created based on the average male face. Six sets of faces from across the social dominance hierarchy were used. Dominant faces tend to express maturity and confidence through face shape (i.e., face width). Interestingly, many people perceive dominant faces as being angry, this perception is important to detect threats and can override facial shape cues. 

Participants were seated in front of a computer and brain responses were recorded via electroencephalogram (EEG). 

Based on FPVS methodology, the same stimulus presented repeatedly at a high frequency rate will elicit brain activity that is synchronized with the presentation rate, such that a steady response is emitted from the brain. Furthermore, a measurable response is elicited if there is a substantial change in the stimuli presented (e.g., from low-dominance faces to a high-dominance one). Assessing these responses using EEG allows researchers to determine an individual’s sensitivity to discriminating between different dominance-related facial features.

In the experimental condition, twelve pictures were presented: 6 high-dominance faces and 6 low-dominance faces. During a trial, high- and low-dominance faces were presented in an alternating pattern and participants were asked to pay attention to the color of a point located on a face, and to indicate (by pressing the spacebar) when the point changed color. 

Eight participants started their trial viewing a high-dominance face first and 7 participants began by viewing a low-dominance face first. Pictures of faces were presented at a rate of six images per second, such that faces of high and low dominance were alternated (e.g., ABABAB).

Because of this presentation rate, the researchers predicted that alternating dominant and non-dominant faces would elicit the asymmetrical brain responses patterns in question every 333ms. A significant change in brain activity associated with viewing alternating faces (as compared to the control tasks which used all dominant or all non-dominant faces) would suggest that high and low dominance faces are processed in distinct ways.

The results supported the hypothesis. In the experimental condition (alternating faces), brain activity was synchronized with the rate at which faces are presented but a large amplitude brain response occured when the level of social dominance within a face did not correspond to the same level of social dominance in the next face shown (at 333ms). This significant brain response provides evidence that individuals can rapidly discriminate faces in relation to different levels of social dominance.

Humans have an innate ability to process trait-dominance in faces of individuals within a social hierarchy. This automatic facial processing provides an advantage to whoever can act on the detection of a higher-ranked individual and capitalize on the resources they may provide.