For group page, The Social Brain.
evil_meter.png
Courtesy: http://confessionsofadoubtingthomas.blogspot.ca/

The neurobiology of moral behaviour is the scientific study of the neurological and biological basis of behaviour that underlies decision-making in moral dilemmas. These behaviours involve many parallel cognitive processes, including complex social, emotional circuitry responsible for behaviour and emotions such as disgust, trust, and moral decisions (1). Specifically, moral behaviour is a result of reasoning and judgment based on one’s understanding of social norms, and the attribution of intentions, beliefs, and emotions to oneself and other people (2). In addition, regions of the brain such as the right ventromedial prefrontal cortex, orbitofrontal cortex, amygdala and the right temporoparietal junction have been implicated in aversive social learning, social cues such as intention and attaching social and emotional value to environmental stimuli to bias decisions of moral dilemmas (3). This area of social cognitive neuroscience relies on techniques such as positron emission tomography (PET), functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS) and the observation of individuals with lesions in associated brain areas and those who exhibit abnormal moral behaviour. Finally, many researchers within the field of neuroethics, such as Michael Gazzaniga, believe that if there exists a set of biological responses to moral dilemmas (a set of ethics), then if we are able to discover these inherent ethical rules, then we may be able to identify rules and implement a set of ethics that aligns with norms socially and biologically (4).

Contents

1 Working Model of Moral Cognition
2 Neuroanatomical Correlates
3 Chemical Correlates
4 Development
5 Utilitarianism
6 Dysfunction of Moral Behaviour
7 References

photo1_(5).jpg
Areas for affective (mPFC) and cognitive (dlPFC) neural circuitry implicated in moral behaviour (Forbes & Grafman, 2010).

Working Model of Moral Cognition


Moral behaviour is thought to be an adaptive social behaviour that exists to meet social demands (5). Since there is no precise location of morality in the human brain, it is thought that moral behaviour is a functional network within existing cognitive and affective circuitry (4). When the separate rational/cognitive and affective neural circuitry work in response to a moral dilemma, the two neural networks 'compete' to influence the decision of the individual (1). The affective circuity is supposedly specifically mediated by the medial Prefrontal Cortex, while rational circuity is dominated by the Dorsolateral Prefrontal Cortex (21). Thus, when cognitive, rational circuits outweigh the affective, utilitarian judgments are made, and emotional responses when the affective, limbic circuits outcompete (1). Furthermore, frontal regions and the anterior cingulate cortex (responsible for conflict detection) become activated in more difficult moral dilemmas, and thus executive functions bias the competition between the two circuits to influence the individual's decision (1).

Neuroanatomical Correlates


Many areas of the brain, including loci responsible cognitive and affective mental states, have been implicated in the appraisal of moral situations and the reactions of individuals to emotionally-intensive moral scenarios. Specifically, affective moral states of the limbic system, and abstract moral reasoning stemming from executive function in frontal areas of the brain are thought to be important for the neural circuitry of moral cognition and decision-making (6). The following are the four main areas implicated in moral appraisals and judgments:

Picture_5.png
Areas of the brain implicated in moral behaviour (Moll, de Oliveira-Souza & Eslinger, 2003).


Ventromedial Prefrontal Cortex

The Ventromedial Prefrontal Cortex (vmPFC) is found on the middle, inferior portion of the frontal lobe, with extensions to Brodmann Area 10 (7). The vmPFC has been implicated in organization of moral behaviour - specifically the predictions of the outcome of moral decisions, and the evaluation of behaviour with regards to moral associative learning (8). In addition, the vmPFC and the frontopolar cortex (BA10) activate together with limbic structures of the brain - the anterior temporal cortex, superior temporal sulcus region and internal limbic structures - to give way to a concept of the 'affective moral brain' (8). In addition, the vmPFC projects to basal and brainstem regions to dictate the visceral responses to emotional stimuli (9). This means that the vmPFC works in concert with areas of the brain responsible for emotion to elicit an emotional response to morally relevant stimuli.

Damage to the vmPFC yields noticeable behavioural changes to the individual. For example, utilitarian decisions in moral dilemmas are more common in subjects with such damage. One case of a moral dilemma used involves a speeding trolley down a track, on route to run over five unsuspecting victims. The individual has the option of either letting the trolley kill the five people, or push another individual into the trolley's way, stopping the trolley from killing the five. Utilitarian decisions to such moral dilemmas strive to achieve the greatest amount of happiness for the most amount of people, regardless of the severity of the actions to achieve such a consequence. The answer to the dilemma using utilitarian calculus would be to push the individual into the trolley's path to save the five, since more people are saved and the aggregate welfare of people is higher than letting the five die. Subjects with vmPFC lesions are known to opt for the utilitarian option in moral situations, as if there was no affective consideration to "compete with the utilitarian appraisal of the dilemma" (1). In addition, vmPFC damage has been implicated in the 'emotional blunting' (8) of individuals, and the reduction in performance in the Iowa Gambling Task (7). Research has shown that individuals with vmPFC lesions exhibit an absence of anticipatory galvanic skin response, a visceral emotional response, to stimuli in the Iowa Gambling Task (7). Consequently, individuals choose poorly on the Iowa Gambling Task because they are insensitive to future affective implications of their decisions, much like their utilitarian decisions in trolley-case moral dilemmas.


Orbitofrontal Cortex

Like the vmPFC, the Orbitofrontal Cortex (OFC) is also thought to be involved in reward-mediated decision-making and outcome expectancy with regards to moral dilemmas (10). Damage to this area is implicated personality changes, poor sociability and a defective ability to make empathizing decisions (10). One such case study, H.N., exhibited marked difficulty making decisions in the Iowa Gambling Task, and decisions that involved heavy consideration of emotional signals (10). In addition, H.N. had average scores for executive function, yet performed poorly for tests involving decision-making and recognition of facial expression (10). Thus, the OFC is implicated in decisions regarding emotional stimuli and the coordination of such stimuli with final decisions in moral and emotional dilemmas.

Right Temporoparietal Junction

The Right Temporoparietal Junction (RTPJ) is thought to assess the intentions and beliefs of others when making moral appraisals to a situation (1). The RTPJ shows increased activity when subjects read about a person's beliefs in moral and non-moral situations (11). Recent research has shown that the RTPJ is important for the evaluation of intentions when making judgments of a situation. For example, Transcranial Magnetic Stimulation has been used to disrupt normal RTPJ function before and during moral judgment. When subjects observe specific scenarios which one actor intends and unsuccessfully attempts to harm another, and RTPJ function is disrupted by TMS, subjects will rate such attempted harms as less morally impermissible than controls (11). In addition, split brain patients when assessing the morality of a situation rely on consequences rather than subjects' intentions (1). This may be because of a disconnect between the dominant (left) hemisphere for language and the RTPJ.


Video: PBS Nova's explanation of TMS on the RTPJ.

Amygdala

The Amygdala has been implicated in learning, and the association of actions that harm other individuals with an aversive response to the victims' stress in a moral context (12). As a result, the amygdala links specific stimuli and actions involving the harm of others to negative affective responses. In addition, deficits in amygdalar function are thought to be involved in the emergence of psychopathy and other forms of severe moral transgressions (12). Psychopaths exhibit reduced amygdalar activity when making moral judgments, and a disability to learn good from bad because of an inability to experience aversive mental states when engaging in harmful, immoral activities (12). Thus, aversive moral stimuli such as fear and the distress of others negatively reinforces the actions of the individual, effectively preventing the individual from repeating actions that cause such stimuli.

Chemical Correlates


Oxytocin

Oxytocin is thought to be involved in altruism and prosocial behaviour between strangers (13). In studies involving transnasal oxytocin infusions, it was seen that an increase of oxytocin induces increased charitable donations to strangers (13). In Barraza et al's (2011) study, subjects were matched with an anonymous partner and given the choice to donate none, all, or a portion of their allocated funds (of $10.00) to the matched participant. The monetary value of donations, and not the percentage of subjects who gave a charitable donation, increased as a result of oxytocin infusions in this example of altruistic behaviour (13). Specifically, "among the 36% of people that did [donate], people with oxytocin were found to donate 48% more to charity than a placebo" (13). As a result, increased oxytocin promotes prosocial behaviour such as altruism towards strangers, and is implicated in behaviours that dictate morality.


Video: A TED talk outlining oxytocin's effect on trust and altruism.

Serotonin

Recent research has suggested that serotonin plays an important role in ethical decision-making. When given a moral dilemma in which one decision would cause the harm of others and a selective serotonin reuptake inhibitor (SSRI), healthy subjects are less likely to choose options that cause the infliction of harm to another (14). In addition, it is believed that serotonin increases an individual's ability to control emotional intuitions that lead to decisions that harm others and works within amygdalar structures to increase the subject's sensitivity to the processing of threats and social signals (14). Possible clinical uses of this could include the manipulation of prosocial behaviour in those afflicted with social dysfunction, such as acquired sociopathy mental illness, schizophrenia and antisocial disorders (14). Thus, SSRIs may be a candidate for the regulation of prosocial, moral behaviour, as serotonin has been implicated to make individuals less likely to opt for decisions that may cause personal harm to others.

Development


The neurodevelopment of morality has been seen to develop in childhood and adolescence. Infants as young as six months prefer other people who have engaged in prosocial behaviour (helping another) instead of agents that have attempted to arrest the actions of others (15). Specifically, fronto-temporal connections between the vmPFC and the amygdala increase over time (15). In recent research, individuals ages 4-37 were subjected to videos showing intentional or accidental scenes with consequences that caused harm to people or inanimate objects. While intentional actions causing harm were rated equally by individuals of all ages, emotional moral situations caused stronger empathy in young participants, and increased activity in the amygdala, insula and temporal poles (15), In addition, ratings of deserved punishment varied with age: younger participants' ratings involved harsh punishments when there was harm to scenarios involving harm to objects and people equally, while older participants' ratings were only harsh to scenarios involving harm to people (15). Because of the increased functional activity between the vmPFC and amygdala over time, it is believed that the moral learning system matures as this connection matures (15). Other research has shown differences in activation between adolescents and adults. Participants age 15-53 were subject to pictures depicting moral transgressions and instructed to rate the severity of the transgression while undergoing fMRI (16). It was found that as participants increased in age, BOLD activity in the temporoparietal junction and the posterior cingulate cortex also increased (16). Thus, aversive conditioning to the negative emotional stimuli and the input of the beliefs and intentions of others increases as an individual matures into adulthood.

Picture_3.png
Lesion overlap of the 6 subjects. Colour bar indicates the overlap between subjects in the same voxel (Koenigs, et al, 2007).

Utilitarianism


Utilitarianism is a school of moral thought that involves making decisions that create the greatest amount of happiness. Abnormal function or lesions to the Ventromedial Prefrontal Cortex have been implicated in utilitarian decision-making (9). In one study, 6 subjects containing bilateral damage to the vmPFC evaluated high conflict scenarios in which considerations could either be utilitarian (to maximize happiness) or a strong emotional aversion to the proposed utilitarian action (9). An example of a personal, high conflict scenario would be to push a stranger onto the track of a trolley to save the lives of five people, thus killing the stranger (17). The vmPFC-lesion group was more likely than controls to choose the morally utilitarian option in personal high conflict moral dilemmas (pushing the stranger onto the track, for example) and lacked an emotional response to the potential harm of others in their decision (9). Utilitarian decisions are thought to arise from the Dorsolateral Prefrontal Cortex, an area responsible for rational cognitive control (15). When the rational cognitive control outcompetes visceral emotional intuitive aspects of moral circuitry, utilitarian decisions are naturally favoured. However, in instances where emotional centres such as the vmPFC are silent, rational cognitive areas are always favoured, and thus this supports a dualist account of moral neural circuitry (17).
Picture_4.png
The rTMS group exhibited less utilitarian decisions to moral dilemmas when TMS was applied to the dlPFC (Tassy et al, 2012).




Other research suggests that the right Dorsolateral Prefrontal Cortex plays an important role in controlling emotional impulses to stimuli and thus is implicated in rational cognitive processes responses for utilitarian decisions (18). In one study, subjects opted for the less utilitarian solution to a high conflict moral dilemma when repetitive transcranial magnetic stimulation (rTMS) was applied to the dlPFC (18).


Dysfunction of Moral Behaviour


Frontotemporal Dementia

Frontotemporal dementia (FTD) is a neurodegenerative disorder that affects the temporal and frontal lobes of the brain (19). As atrophy of the frontal and temporal lobes progresses, the neural circuitry responsible for moral judgments too begins to deteriorate. Symptoms of FTD include disruptions in personality, and specifically an 'emotional blunting' or hyporesponsivity to others' emotions in individuals. Those affected appear self-centered, and unresponsive to the needs of others. It is common for affected individuals to engage in theft, automobile hit-and-runs, and inappropriate violent or sexual acts (19). Since the Ventromedial Prefrontal Cortex, Orbitofrontal Cortex and Amygdala are all affected by the neurodegeneration of FTD, the disease acts much like 'moral agnosia,' or the acquired inability to adhere to moral norms and appropriately respond to social or emotional stimuli (19). In addition, bilateral degeneration of the OFC and amygdala in the case study of J.M. show that in early stages of FTD, individuals exhibit normal results on standard executive tests, yet are incapable of abstract reason with regards to the emotions or perceptions of others in relation to their own motivations (7). As such, FTD subjects differ from diagnosed psychopaths because they lack the deviousness and malicious intent seen in psychopathy (7).

Psychopathy

Psychopathy is condition that begins in early childhood in which affected individuals are egocentric, and engage in intentionally malicious antisocial acts that portray a lack of empathy or regard of others' emotions (19) (20). Psychopaths show little autonomic responses during stressors and when shown immoral or violent images, and thus they possess a hypoactive amygdala (19). This means that aversive conditioning in response to punishment or harms inflicted on others ceases to function in those diagnosed with psychopathy. Additionally, voxel-based morphometry on MRI images comparing psychopaths to healthy controls shows that psychopaths possess anatomical differences in specific regions of the brain. Decreased gray matter volume was found in the Orbitofrontal Cortex, the temporal lobes, and the frontal lobes (20), and is consistent with previous findings showing hypoactivity in frontotemporal regions of the brain during tasks such as the Prisoner's Dilemma Game. Psychopaths tested with the Prisoner's Dilemma Game were found to defect and show a disregard for cooperation (20), and fMRI tests reveal that decreased OFC activity may be implicated in decreased empathy and cooperation (19).

Acquired Sociopathy

Acquired sociopathy occurs after brains lesions to areas specific to the neural circuitry of moral behaviour, and involves the defection of individuals to social and moral norms. Often executive function is spared (20) (9). One such case study where upon injury of the Dorsolateral Prefrontal Cortex, sociopathy and poor regulation of conduct with no decrease of general intelligence was acquired (20). While most cases of acquired sociopathy involve lesions to the vmPFC or OFC (19), the following are the symptoms of lesions to three common areas involved in moral neural circuitry:
  • Amygdalar lesions: involved in Kluver-Bucy Syndrome, loss of visceral responsivity to social stimuli (19).
  • vmPFC lesions: affects decision-making, specifically with regards to social or emotional stimuli (19). Furthermore, there is a reduction of social emotions such as compassion, shame, or empathy towards others (9).
  • OFC lesions: impairs appropriateness of response to social or emotional stimuli, and impulsivity (20).

References


1. Funk C.M. & Gazzaniga, M.S. (2009). The functional brain architecture of human morality. Current Opinion in Neurobiology, 19: 678-681.
2. Mendez, M.F. (2006) What frontotemporal dementia reveals about the neurobiological basis of morality. Medical Hypotheses, 67: 411-418.
3. Moll, J., de Oliveira-Souza, R., & Eslinger, P.J. (2003). Morals and the human brain: a working model. NeuroReport, 14(33): 299-305.
4. Leben, D. (2011). Cognitive Neuroscience and Moral Decision-making: Guide or Set Aside? Neuroethics, 4: 163-174.
5. Moll, J., ed Oliveira-Souza, R., & Eslinger, P.J. (2003). Morals and the human brain: a working model. NeuroReport, 13(3): 299-305
6. Decety, J., & Proges, E.C. (2011). Imagining being the agent of actions that carry different moral consequences: An fMRI study. Neuropsychologia, 49: 2994-3001
7. Moll, J., Zahn, R., de Oliveira-Souza, R., Krueger, F., & Grafman, J. (2005). The neural basis of human moral cognition. Nature Reviews, 6: 799-809.
8. Moll, J., & de Oliveira-Souza, R. (2007). Moral judgments, emotions and the utilitarian brain. Trends in Cognitive Sciences, 11(8): 319-321.
9. Koenigs, M., Young, L., Adolphs, R., Tranel, D., Cushman, F., Hauser, M., & Damasio, A. (2007). Damage to the prefrontal cortex increases utilitarian moral judgments. Nature, 446: 908-911.
10. Namiki, C., Yamada, M., Yoshida, H., Hanakawa, T., Fukuyama, H., & Murai, T. (2008). Small orbitofrontal traumatic lesions detected by high resolution MRI in a patient with major behavioural changes. Neurocase, 14(6): 474-479.
11. Young, L., Camprodon, J.A., Hauser, M., Pascual-Leone, A., & Saxe, R. (2010). Disruption of the right temporoparietal junction with transcranial magnetic stimulation reduces the role of beliefs in moral judgments. PNAS, 107(15): 6753-6758.
12. Blair, R.J.R. (2007). The amygdala and ventromedial prefrontal cortex in morality and psychopathy. TRENDS in Cognitive Sciences, 11(9): 387-392.
13. Barraza, J.A., McCullough, M.E., Ahmadi, S., & Zak, P.J. (2011). Oxytocin infusion increases charitable donations regardless of monetary resources. Hormones and Behaviour, 60: 148-151.
14. Tost, H., & Meyer-Lindenberg, A. (2010). I fear for you: A role in serotonin in moral behaviour. PNAS, 107(40): 17071-17072.
15. Decety, J., Michalska, K.J., & Kinzler, K.D. (2012). The Contribution of Emotion and Cognition to Moral Sensitivity: A Neurodevelopmental Study. Cerebral Cortex,22: 209-220.
16. Harenski, C.L., Harenski, K.A., Shane, M.S., Kiehl, K.A. (2012). Neural development of mentalizing in moral judgment from adolescence to adulthood. Developmental Cognitive Neuroscience, 2: 162-173.
17. Moll, J., & de Oliveira-Souza, R. (2007). Moral judgments, emotions and the utilitarian brain. Trends in Cognitive Sciences, 11(8): 319-321.
18. Tassy, S., Oullier, O., Duclos, Y., Coulon, O., Mancini, J., Deruelle, C., Attarian, S., Felician, O., & Wicker, B. (2012). Disrupting the right prefrontal cortex alters moral judgment. SCAN , 7(3): 282-288.
19. Mendez, M.F. (2006). What frontotemporal dementia reveals about the neurobiological basis of morality. Medical Hypothesis, 67: 411-418.
20. De Oliveira-Souza, R., & Moll, J. (2009). The neural bases of normal and deviant moral cognition and behaviour. Top Magn Reson Imaging, 20(5): 261-270.
21. Forbes, C., & Grafman, J. (2010). The Role of the Human Prefrontal Cortex in Social Cognition and Moral Judgment. Annual Review of Neuroscience, 33(1): 299-324