Do Human Beings Have A “Kill Switch”?


The term “kill switch” normally refers to a fail safe of some sort that brings a compromised system down. The term, insofar as it is used here, is meant to capture the unique anatomy and physiology that makes a psychopathic killer’s brain what it is. Can the switch be flipped in a normal brain? To understand what sorts of malfunctions and abnormalities underlie violent sociopathic behavior, it is necessary to first outline how it is prevented in normal individuals. Then we can begin to understand what reinforcement processes maintain such behaviors in violent psychopaths. Morals, culture, empathy, and emotions, in addition to negative consequences and numerous other factors, likely play a large part in keeping violent behavior under control.

The extent to which science can inform us on our sense of morality is a controversial issue, with positions ranging from complete dependence to total noninvolvement. For example, Sam Harris’s book “The Moral Landscape: How Science Can Determine Human Values” describes how science can be implemented to guide moral decisions. Many agree with the position that science should be involved, and feel that pragmatic analyses can be applied to morally ambiguous situations in order to obtain directions to the moral high ground.

Still, some feel that science has no place in the moral venue, and that this dimension of humanity is the purview of religion exclusively. Others feel it is simply a gut thing, in that one just feels what is right and wrong when presented with a moral dilemma. While the debate rages on, scientific progress on our understanding of how decision making is accomplished by the brain continues to grow. If this area of research can reveal what is involved in normal moral processing, can it also shed light on what goes on in an immoral brain?

Researchers have taken to studying how decisions with moral implications are made from a psychological and philosophical perspective. Moral decisions have been dissected in many studies where humans are asked to make tough choices. For instance, Mina Cikara and her colleagues found that humans are more likely to view sacrificing a single life to save multiple lives (by diverting a runaway trolley) as acceptable if the person being sacrificed fits certain categories, like simply not being part of the same social group as the evaluator or being a person of poor moral character.

The reasoning typically given by subjects in these studies who’ve made the decision to take a life involves the idea that “the needs of the many outweigh the needs of the few … or the one,” to quote Mr. Spock. While the benefits of saving an in-group member can be readily understood and explained through self-serving biases, when more global personal details are added, the reasoning becomes less abstract. For example, if the individual will one day cure cancer, then, given that knowledge, the reason not to intervene clearly follows the numbers. Functional MRI studies using these tasks can begin to provide some insight into how the parts of the brain involved in these sorts of decisions correlate with what is known about the neural control of choice in nonhuman animals.

A large body of literature exists in which choice is investigated at the behavioral and neural level in nonhuman animals. Of course, the choices in these studies boil down to which lever to press, which arm of a maze to enter or which flavor solution is safe to drink. Nevertheless, the information gathered by studies of this nature may begin to identify some of the critical brain areas involved in moral choices. Areas like the limbic system and basal ganglia as well as the orbitofrontal cortex are found to work together in guiding choices of the sorts in animal studies mentioned above. When these circuits are artificially manipulated, choice behavior is impaired.

Parts of the limbic system (which includes the amygdala) and frontal lobes that have been implicated in mediating choice behavior have also been found to be dysfunctional in individuals with antisocial personality disorder (or psychopathy) relative to controls. Additionally, interactions between these areas that normally regulate aggression are impaired in this group, resulting in inappropriate displays of aggressive behavior. Perhaps the impairments in producing emotions and increased aggression arise from the same neural abnormalities and dysfunctions.

Morphological differences in the brain exist between “normal” people and those who are capable of (and experienced with) killing. However, little is known about how these differences support and respond to the act of killing — what happens to the brain when its owner kills? Do these subtle differences in brain anatomy result in the “moral landscape” (as Harris discusses) conducive to murder? How do these differences in anatomy translate to differences in functionality?

Jon Ronson in his book “The Psychopath Test: A Journey Through the Madness Industry” discusses a multitude of studies in which psychopathic individuals show blunted affect to emotionally evocative imagery, such as the scene of a brutal homicide. Moreover, some experience feelings of sexual arousal instead of the normal feelings of disgust. Imaging data shows reduced limbic activation (specifically in the amygdala) in psychopaths when viewing these images relative to normal controls.

Adrian Raine performed a study using PET scans (which measure absorption of the brain’s primary fuel, glucose) and a perceptually based decision-making task in which normal people were compared to a group of individuals who had pled not guilty by reason of insanity to murder charges (NGRI). The NGRI group did not contest that they had committed murder, only that they had not been able to stop themselves due to psychological problems. The NGRI group showed less glucose absorption compared to normal people in key areas of the brain relating to aggression and emotion, such as the prefrontal cortex and corpus callosum, as well as other areas.

Importantly, there was also an asymmetry of activation in the amygdala for the NGRI group; more activity was seen in the right-amygdala complex, suggesting that the amygdala in the left hemisphere was not working on all cylinders. Because the amygdala is a crucial component of the circuit that processes emotionally evocative stimuli and generates aggressive behavior, this impairment can potentially play a large role in removing the inhibitions that normally suppress violent behavior.

This neural profile of dysfunction in emotional processing can begin to provide a basis for why decisions to act violently are made in the first place — these structures have repeatedly been implicated in choice studies using human and nonhuman animals. However, the maintenance or avoidance of future violent behaviors is not addressed. The compromised emotional processing in these individuals does not handle things like guilt and empathy very well.

Therefore, it is not likely that after-the-fact revaluation of violent actions such as murder provides a deterring force like guilt against future violence. Seeing the aftermath of what they’ve done will not send the killer into a remorseful, introspective journey; rather, pleasure is likely experienced. This is suggested by the observation of sexual arousal in psychopaths when viewing images of violence. Is this sexual pleasure part of the reason for repeat offense? Do these sexual sensations become linked with the actions involved in killing through associative processes?

While crosswired reinforcement and sexual circuits in the brain may give some explanation why violent psychopaths enjoy the processes and rituals involved with a kill, killing is in no way confined to psychopathic populations. Conflict all too frequently calls for violence and killing among individuals who would not normally take part in such behavior. While culture normally puts a taboo on taking a life, war can make killing into a more appropriate activity. In the documentary “The Act of Killing” Joshua Oppenheimer gathers reminiscences by men who had taken part in the Indonesian killings of 1965 to 1966. Because the groups responsible for these mass killings wound up on top in the end of the conflict, the slaughter is openly discussed today. While some men appear to experience remorse (for example, bad dreams) for causing so much death, others are quite proud and seem comfortable with what they’ve done.

Granted, while war allows psychopaths to run uninhibited onto the killing fields, every man in this group is not a psychopath — that would be quite a statistical anomaly. Some appear to have grown to at least enjoy the status that their kills have won them (if not the process itself ). While social reinforcement could explain this phenomenon, it appears to be a totally different mechanism than what operates in psychopaths who seemingly enjoy the process over anything else. Maybe there are multiple kill switches in the brain, some with much more worrisome implications than others.

This article was originally published in Brain World Magazine’s Winter 2014 issue.

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