Law, Responsibility, and the Brain

A rchaeological discoveries of traumatic injuries in primitive hominid skulls strongly hint that our species has a long history of violence [1]. Despite repeated attempts throughout history, including efforts to eliminate violence through the imposition of criminal sanctions, we have yet to dispel our violent nature. Consequently, criminal violence remains a common feature of most societies. As policy-makers seek deeper understandings of criminally violent and antisocial behaviour, many contemporary neuroscientists assume that the essential ingredients of the human condition, including free will, empathy, and morality, are the calculable consequences of an immense assembly of neurons fi ring. Intuitively, this view opposes Cartesian dualism (i.e., the brain and mind are separate, but interacting, entities) and assumes that violence and antisocial behaviour emanate from a mechanistically determined brain (see Box 1). From this standpoint, the exciting discoveries of neuroscience resonate far beyond mere philosophical banter and may have important implications for the way government institutions, including education and legal systems, operate. For example, to the extent that legal systems attempt both to move behaviour in socially desirable directions and also to adjudicate transgressions fairly, the legal system's effectiveness can be improved by deepening our understandings about why people behave as they do and both how and why people respond to various changes in legal incentives. Specifi cally, neuroscience may have important implications for both how we understand the multiple infl uences on violent behaviour and how the legal system may better engage with violent criminals. The birth of what may be coined modern " forensic neurology " lies in John Harlow's 19th century observations of Phineas P. Gage [2]. Gage, a railroad worker, suffered the unfortunate experience of having an iron bar blasted through the front of his brain, which resulted in extensive damage to the prefrontal cortex (PFC). Despite Gage's miraculous physical and intellectual recovery, conspicuous changes in his personality were reported. Briefl y, the once courteous and diligent man became explicitly antisocial. As Gage's friends famously articulated, " Gage is no longer Gage ". Since Harlow's lurid description, computerized reconstructions based on Gage's skull fractures have determined more precisely the damaged PFC regions, which current evidence associates with autonomic, social, and affect regulation [3]. The case of Phineas Gage is compelling to both neuroscientists and legal thinkers because it provided the fi rst indication that reasoning and regard for others can be compromised by frontal lobe injury. Harlow's observations have …