Neuroscience is the scientific study of the nervous system. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, developmental biology, cytology, mathematical modeling, and psychology to understand the fundamental and emergent properties of neurons and neural circuit. Neuroscience is the empirical study of the brain and connected nervous system, and contemporary neuroscience seeks to explain how human behaviour arises from brain activity. This is not an easy task. The human brain contains around one hundred billion (1011) nerve cells or neurons and one hundred trillion (1014) synapses or connections between nerve cells. But, over the past thirty years, neuroscientists have made remarkable progress.
Neuroscience has shed light on how the brain and certain mental processes can work, and research is showing just how complex the links between brain activity, mental processes and behaviour really are. For example, neuroscience has shown correlations between patterns of activity in the human brain, mental functions (such as thinking, feeling, sensing, attention, memory and consciousness) and particular In the United States, the MacArthur Foundation has funded a major programme of work on neuroscience and the law, and at least one university now runs a graduate seminar course on ‘Neurolaw’.
The French government has also been funding a programme on ‘Neuroscience and Public Policy’ since 2009, and the European Science Foundation funds a European Neuroscience and Society Network. Research has shown that both genes and the environment can affect mental functions, patterns of brain activity and behaviour. It is known that interactions between genes and environment affect changes in the brain and that the brain continues to develop beyond adolescence and into adulthood. But it is also important to recognise that there is no direct mapping of mental function to specific areas of the brain, and that there are huge differences between individuals.
The application of findings such as these (and many others) to the law may not be as simple as in other disciplines. The remit of this report is to discuss the relevance and utility of these findings from neuroscience to the law. In what follows, a relatively broad view of ‘neuroscience’ is taken, to include some discussion of behavioural genetics and psychology. At present there may be relatively little neuroscience that can be directly applied to the law, but this will surely change over the next ten to twenty years.
This report also takes a broad view of ‘the law’ (although perhaps with more emphasis on criminal than civil law), and has attempted to consider not only what happens in court trials, but also, for instance, what happens in sentencing and probation. It has not been possible within the scope of this report to discuss every possible interaction of neuroscience and law. Instead, some key areas of debate are highlighted, with examples that refer to the legal system of England and Wales, except where stated where stated otherwise. As investigation of the relationship between brain and mind has developed, researchers have been able to describe mental processes that relate nerve cells or neural circuits to the behaviour of individuals. Many of these mental processes such as thinking, feeling, sensing, attention, memory, and consciousness are regularly used in common language. But although mental processes are helpful in explaining the relationship between brain and mind, the mappings from brain activity to mental process and from mental process to bahaviour, remain complex and poorly understood.
Moreover, most experiments that investigate the relationship between brain activity and behaviour necessarily use simplified laboratory situations. Generalising findings from these experiments to complex ‘real world’ situations is difficult and uncertain. An appreciation of the limits of neuroscientific techniques can inform the assessment of how useful these findings can be, and importantly, highlight areas for productive research. The brain is constantly changing. There is variation been individuals in the structure and function of the brain and the mental processes that underpin behaviour. Indeed, everyday experience shows that individuals respond very differently to specifi c situations. Why is that? Evidence suggests that both genes and the environment, and hence people’s unique, individual, lifelong experiences, play a role in modulating behaviour. However genetic influences on the brain are not yet well understood.
Genetic predispositions may have an effect on behaviour, but examples where a simple genetic defect alone can act to affect behaviour are rare. An example from the fi eld of health would be the gene mutation for Huntington’s disease. In the majority of cases, multiple genes affect behaviour, and their individual effects would be very small.
In addition, the physical and behavioural attributes linked to specific genes are affected by a range of environmental factors, including diet, exposure to toxins and social interactions. One of the most important discoveries about the human brain has been that there is a systematic relationship between particular brain areas and particular functions.
For example, the brain areas associated with vision are located in the occipital lobe at the back of the brain. However, it is now clear that such consistent relationships between a brain structure and a mental process are not straightforward ‘one-to-one’ links. Instead, a particular brain structure may be involved in many (but not all) mental processes; and a particular mental process will often involve several (but not all) brain areas. This ‘many-to-many’ mapping of mental processes onto brain areas or structures makes it difficult if not impossible to infer particular mental processes from the observation of activity in a particular area.
The presence of brain activity in a particular area may result from several different mental processes for example those of pain perception, arousal and affect. The ‘fallacy of reverse inference refers to the misguided and incorrect attempt to conclude from observation of activity in an area that a particular mental process was taking place. This is rarely possible.
Neuroscience may also help to provide an understanding of how early adversity alters brain development. Adults who have suffered from adverse early experiences are more likely to demonstrate elevated levels of risk taking behaviours, akin to the behavioural characteristic of adolescence. Studies have revealed that these adults also show heightened neural response in subcortical limbic brain regions during reward processing tasks.