Social Neuroscience: From Neural Mechanisms to Social Behaviour
Social neuroscience is the study of the role of biological systems in implementing social behaviour. This allows the study of neural and hormonal mechanisms to inform our understanding of social structures and behavioural decisions. Specific advantageous physical attributes become prevalent in a species as a result of natural selection; the characteristic gives the individual a survival advantage, so the genetic mutation is more likely to be passed on to future generations. Social behaviours similarly contribute to survival and chance of reproduction, so the neural and hormonal mechanisms responsible are likely to become more prevalent in the population over generations. The brain mediates social interactions through a range of mechanisms.
Phineas Gage:
Phineas Gage suffered a brain injury in 1848 when a tamping rod (a long hollow cylinder of iron) was propelled through his skull, entering through his left cheekbone and exiting through the top of his head. Much of the brain’s left frontal lobe was destroyed. Gage’s survival was miraculous, and he effectively made a complete physical recovery, retaining basic perceptual, motor, and intellectual abilities. However, the injury resulted in a notable and lasting alteration to Gage’s character, described as ‘mental manifestations’. Friends and acquaintances stated that he was ‘radically changed’, to the extent of being deemed ‘no longer Gage’. The primary effect seemed to be a loss of social inhibitions, and this case study led to the development of our understanding of the role of the frontal cortex in cognition and decision-making. The frontal cortex is integral to personality and behaviour, and it seems that the accident also damaged the connections between the frontal cortex and the limbic system, which are involved in the regulation of emotions. This case study was part of the beginning of modern neuropsychology, and one of the first direct links between physical damage to brain areas and social deficits.
Theories of social cognition:
Social cognition uses a number of theories to explain certain principles and debates: the domain specificity debate; theory theory; and simulation theory.
The information processed by the brain in social cognition can be classified into the distinct ‘domains’ of the social (e.g. moral issues, tradition, social norms), and the personal (e.g. privacy, bodily integrity and control). Each domain consists of an organised system of social knowledge. In the ‘domain general’ theory of cognition, a single brain area responds to and processes both social and personal information. In the ‘domain specific’ theory, social and personal information are processed in separate brain regions. There is evidence for both theories across brain areas and behaviours, and it is likely that the true conclusion is not a simple categorization.
‘Theory theory’ proposes that individuals each hold a basic theory of psychology, used to infer the mental states of others. This presumed information about the beliefs, desires or emotions of others is applied to understand the intentions behind a behaviour, or to predict the future actions of another individual. This is sometimes described as ‘perspective taking’; the use of theoretical knowledge to make inferences about another person’s inner state. This is a crucial concept for social understanding, and the ‘inner theory’ is necessarily developed throughout childhood. The development of this social understanding is comparable to the way that a scientific theory is proposed and refined; data is gathered through observation, hypotheses are made and tested, and the accumulation of data facilitates revision and adjustment of the theory.
Simulation theory states that we understand the minds of others via a process of simulation, or ‘putting ourselves in another’s shoes’. This is supported by a particular neuroscientific finding, called the mirror neuron. Mirror neurons are neurons that fire both when an animal performs an action, and crucially also when the animal observes the same action performed by another. In this way, the neuron ‘mirrors’ the observed behaviour, as though the observer was acting. These mirroring mechanisms are proposed to be the basis of a direct form of action understanding, called intentional attunement. When two people interact, they often mimic the posture, mannerisms, and facial expressions of the other, in a phenomenon known as the chameleon effect. This mimicry results in a more successful interaction and the partners like each other better. Mimicry also increases the incidence of prosocial behaviour: behaviour that benefits other individuals or a group, such as helping, sharing, donating, co-operating, or volunteering. This suggests that affiliative behaviour like the chameleon effect causes us to make decisions with greater emphasis on the collective benefits of the group, rather than the self.
Empathy:
Empathy is defined as the ability to share the affective experiences of others; it is a response to the directly perceived, imagined, or inferred feeling state of another being. Sympathy and compassion can then result from empathy. It is suggested that the same brain areas involved in representing one’s own subjective feeling state, such as pain, may also be used in processing vicarious feelings, such as when the pain of another is perceived. Observation of the emotions of others often leads to overt mimicry, seen in cases like wincing when watching another person in pain. Prosocial learning is modulated by empathy; a positive prosocial learning rate connotes a high empathy score.
Perceiving others:
Notable specialisations have been observed within sensory and multisensory areas for the processing of stimuli with strong social relevance. These perceptual specialisations for social stimuli allow human brains to develop complex social cognitive skills, necessary for success in the modern social world. Perhaps the most well-documented case of such a specialisation, is the region in the ventral visual cortex used to process faces. When subjects are shown a range of visual stimuli, it is only the faces that evoke a response in this area. Furthermore, when the region is electrically stimulated, this can result in a temporary inability to name familiar faces. Damage to this area results in an impairment called prosopagnosia or ‘face blindness’, the inability to recognise familiar faces, including one’s own. These findings support the theory that this area, called the fusiform face area, is specialised for the recognition of faces, contributing to social function.
Another brain area with specialisations for processing socially pertinent stimuli, is the superior temporal sulcus, which processes body parts, biological motion, gaze, and mouth movements. This area seems to manage gaze direction and the perception of mouth movements, which has applications in lip-reading. However, this area seems to be more activated by perception of the self, rather than a friend, and a friend more than a stranger. As such, the superior temporal sulcus can provide evidence for both domain specific and domain general theories. The specialisation of the area for biological motion implies a domain specific arrangement, but the additional activation for stimuli relating to the self supports a domain general theory.
Mentalising:
Humans experience mental states, and can also infer the mental states of others, such as desires, attitudes and beliefs. This ability is called mentalising. Mentalising must be imaginative, because we cannot know the thoughts of others, and it is a vital skill for social function and self-organisation. The ability to infer other people’s mental states may be uniquely human, and has allowed us to predict and interpret the actions of others in a range of competitive and cooperative situations. The extent to which we are able to hone this crucial skill is decided predominantly by our genetic inheritance and early experiences. One of the most important early experiences is the development of secure attachment relationships, which give infants the opportunity to develop social intelligence and mentalisation skills. Furthermore, our understanding of ourselves as mental agents stems from interpersonal experience, primarily the child-caregiver relationship. As such, the ability to mentalise may demonstrably be compromised by a lack of opportunity to be understood and thought about by a sensitive caregiver, and this increases the risk of developing personality pathology.
The brain areas involved in mentalising include the dorsomedial prefrontal cortex, superior temporal sulcus, and the temporal pole, and these areas are often found to be engaged during the idling default mode of the brain. Similar areas are also activated in remembering or thinking about the future (prospecting). Therefore, the default mode of the brain may be focused on making plans or drawing appraisals based on memory and projecting.
The social brain:
The ‘social brain’ may have developed due to the unique evolutionary pressures that result from living in groups. Specific brain areas have been found to be specialised and particularly responsive during social interactions, and not activated in non-social conditions. There is clear evidence for mirroring systems in the brain, which contributes to understanding and empathy, but more complex contributors to and repercussions of social behaviour still need to be studied on a neural level. At a species level, the large brain size of humans relative to other primates could be reflective of the increased complexity of human social environments. Between individuals, there is more grey matter in the anterior cingulate cortex and the superior temporal sulcus in people with larger social networks. Furthermore, skill in navigating social networks is clearly an evolutionary advantage, and it is seen in male macaque monkeys, where more offspring are fathered when the male adopts a more dominant social position. Social interactions and networks are integral to our everyday lives, and the importance is reflected in physiological evidence. The neural mechanisms are yet to be fully elucidated, and this makes social neuroscience a rapidly developing and relevant field today.
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