ERPs responses to dominance features from human faces

Unraveling the social hierarchy: Exploring behavioral and neural dynamics in shaping inhibitory control

Inhibitory control is crucial for regulating emotions, suppressing biases, and inhibiting inappropriate responses in social interactions. Social rank, or perceived position in the hierarchy, can influence inhibitory control, with high-rank individuals requiring it to regulate dominant behavior and low-rank individuals requiring it to regulate emotional reactions or avoid submissive behaviors. Furthermore, research suggests that social status can affect the neural mechanisms underlying inhibitory control, leading to differences in abilities and strategies based on perceived rank. In this study, we investigated the effects of social rank on inhibitory control using a dot estimation task to prime social hierarchy. Subsequently, we assessed the inhibitory control of the participants using a Go/Nogo task with photos of individuals in different social ranks. The study recruited a total of 43 students (22 males and 21 females), with a mean age of 26.8 years (SD=4.08). We measured both behavioral (reaction time and response accuracy) and electrophysiological (N200 and P300 event-related potentials) responses to investigate the neural correlates of inhibitory control. Results showed that participants responded slower to lower-rank individuals but had higher accuracy when inhibiting their response to them. The N200 amplitude was greater when presented with higher ranks stimuli in Go trials, indicating greater conflict monitoring, while the P300 amplitude was significantly higher in Nogo trials compared to Go trials. These findings suggest that social rank can influence inhibitory control and highlight the importance of considering the impact of social hierarchy in social interactions.

Toddlers' sensitivity to dominance traits from faces

In adults, seeing individual faces is sufficient to trigger dominance evaluations, even when conflict is absent. From early on, infants represent dyadic dominance relations and they can infer conflict outcomes based on a variety of cues. To date, it is unclear if toddlers also make automatic dominance trait evaluations of individual faces. Here we asked if toddlers are sensitive to dominance traits from faces, and whether their sensitivity depends on their face experience. We employed a visual preference paradigm to study 18- and 24-month-old toddlers' sensitivity to dominance traits from three types of faces: artificial, male, female. When presented with artificial faces (Experiment 1), 18- and 24-month-olds attended longer to the non-dominant faces, but only when they were in upright orientation. For real male faces (Experiment 2), toddlers showed equivalent looking durations to the dominant and non-dominant upright faces. However, when looking at female faces (Experiment 3), toddlers displayed a visual preference for the upright non-dominant faces at 24 months. To our knowledge, this is the first study to show that toddlers already display sensitivity to facial cues of dominance from 18 months of age, at least for artificial face stimuli.

Facial Expression of TIPI Personality and CHMP-Tri Psychopathy Traits in Chimpanzees (Pan troglodytes) : Evidence for Honest Signalling?

Honest signalling theory suggests that humans and chimpanzees can extract socially relevant information relating to personality from the faces of their conspecifics. Humans are also able to extract information from chimpanzees' faces. Here, we examine whether personality characteristics of chimpanzees, including measures of psychopathy, can be discerned based purely on facial morphology in photographs. Twenty-one chimpanzees were given naïve and expert personality ratings on the Ten Item Personality Inventory (TIPI) and the Chimpanzee Triarchic Model of Psychopathy (CHMP-Tri) before and following behavioural observations. Characteristics relating to openness, conscientiousness, extraversion, and disinhibition could be distinguished from the faces of chimpanzees. Individuals higher on disinhibition have lower scores on conscientiousness and emotional stability and higher scores on extraversion, while those higher on meanness have lower conscientiousness and agreeableness. Facial expressions are linked to personality traits present in the TIPI and CHMP-Tri models: the Relaxed Face and the Grooming Face were displayed more by chimpanzees higher on agreeableness, whereas the Compressed Lips Face was observed more in those individuals higher on boldness, and the Full Open Grin was displayed more by chimpanzees higher on extraversion but lower on emotional stability and conscientiousness. Facial expressions were also found to be associated with particular behavioural contexts, namely the Grooming Face in affiliative contexts and the Relaxed and Relaxed Open Mouth Faces in neutral contexts. Dominant chimpanzees display higher levels of boldness and more Compressed Lips Faces, Relaxed Open Mouth Faces, and Grooming Faces than subordinate individuals. These findings support and extend evidence for an honest signalling system and a personality structure shared between humans and chimpanzees. Future research could further explore how personality is conveyed through the face, perhaps through more than just singular aspects of character, and maybe reflecting what chimpanzees themselves are able to do.