Discussion 1: Problem Solving

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Decision Making and Free Will: A Neuroscience Perspectivez

Kelly Burns, J.D. y and Antoine Bechara, Ph.D.*

A thorough analysis of the question of whether we possess ‘‘free will’’ requires that we take into account the process of exercising that will: that is, the neural mechanisms of decision making. Much of what we know about these mech- anisms indicates that decision making is greatly influenced by implicit processes that may not even reach conscious- ness. Moreover, there exist conditions, for example certain types of brain injury or drug addiction, in which an indi- vidual can be said to have a disorder of the will. Examples such as these demonstrate that the idea of freedom of will on which our legal system is based is not supported by the neuroscience of decision making. Using the criminal law as an example, we discuss how new discoveries in neuro- science can serve as a tool for reprioritizing our society’s legal intuitions in a way that leads us to a more effective and humane system. Copyright # 2007 John Wiley & Sons, Ltd.

A visit to one of our nation’s jails or prisons will show rows of humans kept behind

bars, many of whom have returned to prison on a second or third offense, committed

despite their first-hand knowledge of the consequences of their actions. As a society

we justify the imprisonment of such individuals by our belief that one can avoid

incarceration: that someone sentenced to spend years in prison got there only

through his or her own choices. That is, we possess a freedom of will, and it is misuse

of that freedom that justifies restrictions on it.

The question of whether we have free will, whether our actions are determined, or

whether these two possibilities are even mutually exclusive, is one that continues to

be debated in philosophical and scientific circles, but that obviously has important

implications for the foundations of our legal system. Since the core of any free will

that might exist is the ability to make choices, it is important in this debate to think

about the neural mechanisms of human decision making, and whether we have

absolute control over this mechanism or vice versa. Research continues to elucidate

the neural processes underlying how we make our choices, and much of what we

know already about these brain mechanisms indicates that decision-making is greatly

Behavioral Sciences and the Law

Behav. Sci. Law 25: 263–280 (2007) Published online in Wiley InterScience

(www.interscience.wiley.com) DOI: 10.1002/bsl.751

*Correspondence to: Antoine Bechara, Ph.D., Hedco Neuroscience Building (HNB), Suite B26, University of Southern California, Los Angeles, CA 90089-2520, U.S.A. E-mail: [email protected] y Brain and Creativity Institute and Department of Psychology, University of Southern California. z The decision neuroscience research described in this article was supported by NIDA grants DA11779-02, DA12487-03, DA16708, and by NINDS grant NS19632-23.

influenced by implicit processes that do not necessarily reach consciousness.

Furthermore, neurological evidence suggests that focal brain damage can disturb the

normal operation of some of these implicit processes. In such cases the individual

begins to appear as if afflicted with a ‘‘disorder’’ of his or her will, as evidenced by

repeated decisions and actions that are against the person’s best interests, and failure

to learn from repeated mistakes, in spite of perfectly intact intellect, memory and

other cognitions (Bechara, 2003). Thus neuroscience brings us evidence that

questions the idea, which the law assumes, that ‘‘free will’’ is always intact, and as

long as one is cognitively normal, there is no excuse for a person not to be able to

choose between right and wrong.

While recognizing that the continuing free will versus determinism controversy

makes confident acceptance of either idea naive, the legal system nonetheless has

remained attached to the notion of free will as necessary, in its view, for the

maintenance of social order (Cotton, 2005). The Supreme Court even has called free

will a ‘‘‘universal and persistent’ foundation stone in our system of law’’, as

compared with ‘‘a deterministic view of human conduct that is inconsistent with the

underlying precepts of our criminal justice system’’ (United States v. Grayson, 1978).

Several scholars have argued (Cotton, 2005; Greene & Cohen, 2004; Jones, 2003),

however, that neuroscience or other research that seems to undermine the notion of

free will need not be seen as such a threat to our legal system. Rather, this research

provides an opportunity for our society to reexamine the underpinnings of the legal

system, and reprioritize in a way that is more responsive to the facts of human biology

and psychology, and thus more effective.

The following section of this article will outline features of the neuroscience of

decision making that bear upon the question of whether humans have free will. We

will discuss the normal decision-making process, and also focus on a few examples

where this process has been known to break down. In the next section we will explore

the implications of this research for the legal system. While more research is needed

to fully understand the mechanisms of will, what we already know can hopefully

inspire some creative solutions to the societal problems that the legal system

addresses.

THE NEUROSCIENCE OF DECISION MAKING AND WILLPOWER

Willpower, as defined by the Encarta 1

World English Dictionary (2006), is a

combination of determination and self-discipline that enables somebody to do

something despite the difficulties involved. This is the mechanism that enables one

to endure sacrifices now in order to obtain benefits later. Otherwise, how would one

accept the pain of surgery? Why would someone resist the temptation to have

something irresistible, or delay the gratification from something that is appealing?

We will argue that these complex and apparently indeterminist behaviors are the

product of a complex cognitive process sub-served by two separate, but interacting,

neural systems: (1) an impulsive, amygdala-dependent, neural system for signaling

the pain or pleasure of the immediate prospects of an option, and (2) a reflective,

prefrontal-dependent, neural system for signaling the pain or pleasure of the future

prospects of an option. The final decision is determined by the relative strengths of

264 K. Burns and A. Bechara

the pain or pleasure signals associated with immediate or future prospects. When the

immediate prospect is unpleasant, but the future is more pleasant, then the positive

signal of future prospects forms the basis for enduring the unpleasantness of

immediate prospects. This also occurs when the future prospect is even more

pleasant than the immediate one. Otherwise, the immediate prospects predominate,

and decisions shift towards short-term horizons. As suggested by Damasio (1994),

‘‘willpower is just another name for the idea of choosing according to long-term

outcomes rather than short-term ones’’.

We have used the term ‘‘somatic’’ (Damasio, 1994) to refer to the collection of

body-related responses that hallmark these affective and emotional responses.

Somatic refers to the Greek word ‘‘soma’’, i.e. body. Although during the process of

weighing somatic (affective) responses the immediate and future prospects of an

option may trigger numerous somatic responses that conflict with each other, the end

result is that an overall positive or negative somatic state emerges. We have proposed

that the mechanisms that determine the nature of this overall somatic state (i.e.

positive or negative) are consistent with the principles of natural selection, i.e.

survival of the fittest (Bechara & Damasio, 2005). In other words, numerous and

often conflicting somatic states may be triggered at the same time, but stronger ones

gain selective advantage over weaker ones. With each ‘‘thought’’ brought to working

memory, the strength of the somatic state triggered by this ‘‘thought’’ determines

whether the same ‘‘thought’’ is likely to recur (i.e. will be brought back to memory so

that it triggers another somatic state that reinforces the previous one), or whether the

‘‘thought’’ is likely to be eliminated. Thus over the course of pondering a decision,

positive and negative somatic markers that are strong are reinforced, while weak ones

are eliminated. This process of elimination can be very fast. Ultimately, a winner

takes all; an overall, more dominant, somatic state emerges (a ‘‘gut feeling’’ or ‘‘a

hunch’’ so to speak), which then provides signals to the brain that modulate activity

in neural structures involved in biasing decisions. This ‘‘winner takes all’’ view is

consistent with the conception by Strack and Deutsch of competition between motor

schemata (Strack & Deutsch, 2004).

The Somatic Marker Framework

The somatic marker framework provides a system-level neuroanatomical and

cognitive framework for decision making, and for choosing according to long-term

outcomes rather than short-term ones. It suggests that the process of decision

making depends in many important ways on neural substrates that regulate

homeostasis, emotion and feeling (Damasio, 1994).

Somatic states can be induced from (1) primary inducers and (2) secondary

inducers (Damasio, 1995). Primary inducers are innate or learned stimuli that cause

pleasurable or aversive states. Once present in the immediate environment, they

automatically and obligatorily elicit a somatic response. The actual encounter of a

drug by an addicted individual is an example of a primary inducer (Bechara,

Damasio, & Damasio, 2003). Secondary inducers, on the other hand, are entities

generated by the recall of a personal or hypothetical emotional event, i.e. ‘‘thoughts’’

and ‘‘memories’’ of the primary inducer, which elicit a somatic response. The recall

Decision making and free will 265

or imagination of a drug experience by an addicted individual is one example of a

secondary inducer (Bechara et al., 2003).

We have argued that the amygdala is a critical substrate in the neural system

necessary for triggering somatic states from primary inducers. It couples the features

of a primary inducer with the somatic state associated with the inducer. This somatic

state is evoked via effector structures such as the hypothalamus and autonomic

brainstem nuclei that produce changes in internal milieu and visceral structures

along with other effector structures such as the ventral striatum, periaqueductal gray

(PAG), and other brainstem nuclei, which produce changes in facial expression and

specific approach or withdrawal behaviors. The amygdala is one of our evolutionarily

older brain structures, located deep in the medial temporal lobes. Once somatic

states from primary inducers are induced, signals from these somatic states are

relayed to the brain stem and forebrain. Signals from activated somatic states lead to

the development of somatic state patterns in the brainstem (the evolutionary oldest

areas of the brain) or the cortex (the evolutionary newer areas). The perception of

these patterns at the brainstem level is by and large unconscious, but at the level of

the cortex this perception may become conscious in the form of a subjective feeling.

After a somatic state has been triggered by a primary inducer and experienced at

least once, a pattern for this somatic state is formed. The subsequent presentation of

a stimulus that evokes memories about a specific primary inducer will then operate as

a secondary inducer. Secondary inducers are presumed to re-activate the pattern of

somatic state belonging to a specific primary inducer. For example, recalling or

imagining the experience of a drug re-activates the pattern of the somatic state

belonging to the actual previous encounter of that drug. However, the somatic state

generated by the recall or imagination of using a drug (secondary inducer) is usually

fainter than one triggered by an actual use of that drug (primary inducer). The

prefrontal cortex is a brain structure that is both evolutionarily recent and one of the

last structures to develop fully over an individual’s lifespan.

Non-conscious Operation of Somatic States

During the pondering of a decision, somatic states are triggered by primary or

secondary inducers. Once induced, they participate in two functions. In one they

provide a substrate for feeling the induced state. In the other they provide a substrate

for influencing or biasing decisions. Most intriguing is that the presence of these

somatic states and their influence on decision making and behavior need not be

conscious.

A study using the Iowa Gambling Task illustrates this point (Bechara, Damasio,

Tranel & Damasio, 1997). In the Iowa Gambling Task, subjects are given four decks

of cards and $2000 in play money with which to play a game, and are instructed that

their goal in the game is to win as much money as possible. Each time a subject selects

a card, she or he either wins or loses some amount of money. Decks A and B are

disadvantageous decks, where the immediate reward is higher ($100 per card) but

the losses are large, and playing more often from these decks leads to an overall loss.

Decks C and D are advantageous, drawing lower rewards per card ($50), but with

smaller penalties such that playing mostly from these decks leads to an overall gain.

While each subject plays the game, measures are taken of skin conductance

266 K. Burns and A. Bechara

responses (SCRs) to test their non-conscious responses to making card choices.

Subjects are also asked at intervals during the game whether they understand what is

going on in the game, to compare their conscious development of strategy to any

unconscious strategizing that might be underway.

The results of this experiment demonstrate the operation of covert somatic states

in biasing decisions. In the Iowa Gambling Task, normal subjects began to select

advantageously before they consciously developed an understanding of which decks

were advantageous. In addition, these subjects generated an anticipatory SCR before

choosing a card from the disadvantageous decks, and likewise started generating this

response before having conceptualized that these decks were disadvantageous.

Responses can be broken down further into four stages. In the ‘‘pre-punishment’’

stage, before encountering losses, subjects preferred the higher-gain decks. In the

‘‘pre-hunch’’ stage, subjects began to generate SCRs to decks A and B, but all

indicated that they had no clue what was going on in the game. All normal subjects

expressed a ‘‘hunch’’ by about card 50 that A and B were riskier; we called this the

‘‘hunch’’ stage. Eventually most normal subjects expressed an understanding of

which decks were riskier (this was usually by about card 80), in what we called the

‘‘conceptual’’ period. Notably, even subjects who never reached the conceptual

period actually made advantageous choices in playing.

The fact that normal subjects can make advantageous choices without having the

factual knowledge required to logically support those choices has interesting

implications for our understanding of the decision making process and free will.

Research indicates that in the striatum somatic states operate implicitly, using

‘‘knowledge without awareness’’. Other areas of the brain (the anterior cingulate,

and perhaps the adjacent supplementary motor area) bias decision making using

‘‘knowledge with awareness’’; that is, they engage in our common-sense version of

the decision-making process using conscious and explicit knowledge of a decision’s

consequences. So while both conscious and unconscious knowledge are contributing

to the process of choice, the fact that the generation of somatic states can guide us

toward beneficial behaviors without any input from our conscious deliberations

indicates that much behavior that seems to be ‘‘free will’’ may be determined by the

routine operation of a healthy neural mechanism. What happens when something

goes wrong with this process elucidates this point further.

Neural Mechanisms of Willpower

Based on the somatic marker framework, we have proposed that willpower (or lack

thereof) emerges from the dynamic interaction between two separate, but

interacting, neural systems: (1) an impulsive system that triggers somatic states

from primary inducers and (2) a reflective system that triggers somatic states from

secondary inducers. The reflective system controls the impulsive system via several

mechanisms of impulse control. However, this control of the reflective system is not

absolute: Hyperactivity of the impulsive system can overwhelm or ‘‘hijack’’ the

influence of the reflective system.

It is important to note that at the process level the characteristics of the

‘‘impulsive’’ and ‘‘reflective’’ neural systems are similar to the two-system view of

Kahneman and Tversky on ‘‘intuition’’ versus ‘‘reasoning’’ (Kahneman & Tversky,

Decision making and free will 267

1979), or that of Strack and Deutsch on reflective and impulsive determinants of

social behavior (Strack & Deutsch, 2004). In all cases, the distinction is between the

operations of one system that are typically fast, automatic, effortless, implicit and

habitual, and the operations of another system that are slow, deliberate, effortful,

explicit and rule governed. The distinct characteristic of our view is the assignment

of neural substrates and physiological mechanisms for the operations of these

systems.

More specifically, exposure to primary inducers (e.g. drugs) triggers fast,

automatic, and obligatory somatic states via the amygdala system. Somatic states

triggered by the amygdala are short lived and habituate very quickly (Buchel, Morris,

Dolan, & Friston, 1998; Dolan et al., 1996; LaBar, Gatenby, Gore, LeDoux, &

Phelps, 1998). Secondary inducers trigger somatic states via the ventromedial

prefrontal cortex from perceived or recalled mental images. While the amygdala is

engaged in emotional situations requiring a rapid response, i.e. ‘‘low-order’’

emotional reactions arising from relatively automatic processes (Berkowitz, 1993;

LeDoux, 1996), the ventromedial prefrontal cortex is engaged in emotional

situations driven by thoughts and reflection. Once this initial amygdala emotional

response is over, ‘‘high-order’’ emotional reactions begin to arise from relatively

more controlled, higher-order processes involved in thinking, reasoning and

consciousness (Schneider & Shiffrin, 1977). Unlike the amygdala response, which is

sudden and habituates quickly, the ventromedial prefrontal cortex response is

deliberate, slow, and lasts for a long time. Thus the prefrontal cortex helps predict

the emotion of the future, thereby forecasting the consequences of one’s own actions

(see Figure 1).

Once somatic states are triggered via the amygdala or the prefrontal cortex, a

large number of channels can then convey body information to the central nervous

system (e.g. spinal cord and vagus nerve). Furthermore, early evidence suggests

that the biasing action of somatic states on behavior and cognition is mediated, at

least in part, by the release of neurotransmitters, such as the neurotransmitters

dopamine (DA), serotonin (5-HT), noradrenaline (NA) and acetylcholine (Ach).

Indeed, the neurons that manufacture these neurotransmitters are situated in

such a way that, on one end (the dendrite end), they can convey somatic state

signals, which then influence the pattern of neurotransmitter release at the other

end (the axon terminals end). In turn, changes in neurotransmitter release can

modulate synaptic activities of neurons subserving behavior and cognition within

the reflective system. This chain of neural mechanisms provides a way for somatic

states to influence activity in a variety of neural regions important for decision

making. Thus the significance of this neural arrangement is that, regardless of how

somatic states are triggered, i.e. impulsively (primary induction) or reflectively

(secondary induction), once they are triggered, they can gain access to cortical and

subcortical neurons subserving cognition. Thus, depending on their strength, they

have the capacity to modify and influence cognition, especially decision making

(see Figure 1).

Early in life, the reflective system is poorly developed and willpower is relatively

weak. Behavior is more dominated by the impulsive system—children tend to

behave in a manner that they do what they feel like doing right now, without much

thought about the future. However, through learning they learn to constrain many

desires and behaviors that conflict with social rules, and that lead to negative

268 K. Burns and A. Bechara

consequences. This is the first sign of the development of willpower, and an example

of how the reflective system gains control over the impulsive system. This ability, i.e.

to choose according to long-term outcomes, and resist immediate desires, requires

the normal development and normal triggering of somatic states by the reflective

system, which signal the value of long-term outcomes. Deprived of these somatic

states, the reflective system loses its control, and willpower breaks down. Indeed, this

is exactly what happens when areas of the ventromedial prefrontal cortex are

damaged. However, it appears that there is more than one mechanism through which

the reflective system exerts control over the impulsive system.

The functional evolution of the prefrontal cortex appears to involve an

incremental increase in its capacity to access representations of events that occur

in the more distant future. This enhanced ‘‘futuristic’’ capacity coincides with the

development of more rostral/anterior regions of the ventromedial prefrontal cortex.

Comparative studies of the frontal lobes in humans and non-human primates have

revealed that the major advancement in the size, complexity and connectivity of the

frontal lobes in humans relates primarily to Brodmann Area 10, i.e. the frontal pole

(Semendeferi, Armstrong, Schleicher, Zilles, & Van Hoesen, 2001), and not so

much to the more posterior areas of the ventromedial prefrontal cortex

(Semendeferi, Lu, Schenker, & Damasio, 2002). For this reason, we have argued

that there is a distinction between two broad mechanisms of behavioral and cognitive

control.

(1) Decision making, which reflects a tendency to think about the consequences of a

planned act before engaging in that act. It requires knowledge about facts and values,

and it involves conscious, slow and effortful deliberation about consequences that

may or may not happen in a distant future. An example requiring decision making is

finding a briefcase containing $100 000 in a dark alley. The decision to take or not

take the money may require some deliberation about the ethics, morality and

consequences of such an action. The critical neural region for this mechanism of

control is the more anterior region of the ventromedial prefrontal cortex, i.e. that

involving the frontal pole and Brodmann Area 10 (Bechara, 2004). This area is

particularly the cortex area that has evolved so much further in humans than in other

animals, including non-human primates, and this gives us distinguishing cognitive

abilities such as projecting into the future, understanding probabilities and having

the ability to decide and act upon them, and being motivated by abstract principles

beyond daily survival needs.

(2) Impulse control reflects inhibition of a pre-potent act (motor impulse control), or a

pre-potent mental image/thought (attentional impulse control). The learning to quickly

and automatically inhibit such a pre-potent act (or thought) is due, in large part, to

the triggering of a somatic state, which signals the immediate and certain nature

of the consequences. An example of this quick, automatic and implicit mechanism

of impulse control is finding a similar amount of $100,000 spread out on a table

inside a bank. Normally, any thought, intention or impulse to grab the money is

inhibited automatically and effortlessly. The critical neural region for the

mechanism of motor impulse control is the more posterior region of the

ventromedial prefrontal cortex, i.e. that involving the anterior cingulate (Bechara,

2003, 2004). The critical neural region for the mechanism of attentional impulse

control is the lateral orbitofrontal and dorsolateral (inferior frontal gyrus) region

(Bechara, 2003, 2004).

Decision making and free will 269

Loss of Willpower

The complex system that we have outlined above carries with it several distinct but

interrelated ways in which it can fail or be compromised. Choosing according to

long-term outcomes rather than short-term ones requires that the somatic states

triggered by the reflective system dominate those triggered by the impulsive system.

Two broad types of condition could alter this relationship and lead to loss of

willpower: (1) a dysfunctional reflective system and (2) a hyperactive impulsive

system. The neural regions of the reflective system, which exert ‘‘top-down’’ control

on decision making (anterior ventromedial prefrontal cortex), motor impulse control

(anterior cingulate), and perceptual impulse control (lateral orbitofrontal and

dorsolateral), are all targets for the neural systems that convey ‘‘bottom-up’’

influence of somatic signals. The influence of these somatic signals could be

non-conscious and implicit, or conscious and explicit, i.e. accompanied by a certain

feeling of urge. The example of substance dependence, and our research with

dependent individuals, demonstrates how various dysfunctions can affect this

process.

Reflective System Dysfunction

Our research has demonstrated that individuals who are substance dependent, or

those who have suffered bilateral damage to the ventromedial prefrontal cortex, show

similar behavior patterns related to dysfunction of the reflective system. Two

characteristics in particular are relevant to this discussion. First, both groups often

are in denial or unaware that they have any problem. Second, individuals in both

groups tend to act in such a way that brings about immediate reward, even when that

comes at the risk of incurring extremely negative future consequences, which may

include loss of job, home, important life relationships, and reputation, and often

troubles with the law. Such individuals act seemingly in ignorance of this risk.

Examples of this pattern related to substance use cause family strife nationwide and

can be seen in the newspapers every day. The most famous case of prefrontal cortex

injury, if not the most famous case in neuroscience, is that of Phineas Gage. In 1848,

Gage survived a freak construction accident that sent a metal rod through his brain,

obliterating his ventromedial prefrontal cortex without ever causing loss of

consciousness. Gage’s life functions and intellect were miraculously unaffected

by the injury. However, his co-workers described him after the injury as ‘‘no longer

Gage’’, seeing that a man who once had been responsible and a role model for other

workers had become obnoxious, crass, and foolish, and able to behave only in ways

that were sure to bring about personal ruin.

Though at the time of Gage’s injury the neural reasons for this personality change

were unknown, modern neuroscience explains how his cognitive processes had been

disturbed. While normal subjects executing the Iowa Gambling Task generate SCRs

while they consider drawing a card from a disadvantageous deck, subjects with

bilateral prefrontal damage do not generate this response (Bechara et al., 1997). In

other words, their reflective systems are not generating somatic states that help bias

the response away from disadvantageous decisions. The outcomes of these subjects’

decisions are as we might expect: They do not begin to choose advantageously during

270 K. Burns and A. Bechara

the pre-hunch or hunch periods. In fact, these subjects do not even choose

advantageously when they reach the conceptual period, despite the fact that, when

asked, they describe with accuracy what strategy will win the game! Substance

dependent subjects behave on the Iowa Gambling Task just as prefrontal cortex

lesion patients do, and also do not generate SCRs biasing them away from bad

decisions (Bechara, Dolan, & Hindes, 2002). Research in which substance

dependent subjects executed other, similar decision-making tasks has yielded

similar results (Bartzokis et al., 2000; Grant, Bonson, Contoreggi, & London, 1999;

Grant, Contoreggi, & London, 1997, 2000; Mazas, Finn, & Steinmetz, 2000; Petry,

Bickel, & Arnett, 1998; Rogers et al., 1999).

The absence of somatic response is an example of a dysfunction in the

decision-making control mechanisms. The reflective system can also exhibit a failure

or disability in its perceptual or motor impulse control mechanisms. Again using

substance abuse as an example, a substance dependent person might be unable to

suppress the thought of taking the drug, if perceptual control is faulty. If the deficit is

in motor impulse control, the person might act so quickly in response to the drug

stimulus that the person does not even have a chance to think about it.

One way to test impulse control mechanisms is to ask subjects to perform tasks in

response to changing stimuli, and measure their response times. For example, in the

stop-signal paradigm, subjects are shown left and right pointing arrows and are asked

to respond to the arrows, but to inhibit their response when the color of the arrow

changes (the ‘‘stop signal’’). The color changes come occasionally but unpredic-

tably. When this experiment was performed, substance dependent subjects exhibited

quicker response times than normal controls, but significantly longer response times

to the stop signal, reflecting problems with impulse control (Crone, Cutshall,

Recknor, Van den Wildenberg, & Bechara, 2003). Other studies also have

demonstrated difficulties of impulse control associated with drug and alcohol

addiction(Crone et al., 2003; Noel, Van Der Linden, Verbanck, Pelc, & Bechara,

2003; Noel, Van Der Linden, Verbanck, Pelc, & Bechara, 2005).

Impulsive System Hyperactivity

It is also possible for the impulsive system to exaggerate the somatic response of

reward stimuli, resulting in it becoming exceedingly difficult for even a well

functioning reflective system to generate somatic responses that bias the person

toward inhibiting action, or executing will. We might conceptualize this as a

‘‘hijacking’’ of the execution of willpower by an overactive impulsive system, where

will becomes guided by the amygdala rather than by the prefrontal cortex. Research

using varieties of the Iowa Gambling Task has shown exactly this hypersensitivity to

reward in substance dependent subjects. In one experiment, skin conductance

responses in substance dependent subjects were higher in magnitude when

anticipating rewards as compared with normal controls, whereas SCRs when

anticipating punishments were relatively weak (Bechara et al., 2003, 2002). This

concept of impulse control is also supported broadly by some of the prominent work

on impulsivity, such as that by Moeller, Barratt, Swann, and their colleagues

(Moeller, Barratt, Dougherty, Schmitz, & Swann, 2001).

Decision making and free will 271

We have used the example of substance dependence as an illustration of the ways

in which decision-making processes can be compromised. It is important to note that

we are not making any assertions about the roots of substance dependence or coming

to conclusions about whether decision-making impairments are a cause or a result of

the prolonged substance use. Rather, this explanation serves to highlight the

similarities between substance dependent persons and individuals with prefrontal

cortex damage in executing decision-related tasks about subjects that are unrelated

to substance use. The high degree of similarity indicates that, regardless of cause or

prognosis, both populations serve as good examples of what can go wrong in decision

processing, and therefore shed light on what is happening in all cases of

decision-making functioning.

So do we Have Free Will?

Given all of this information about the neural mechanisms of human decision

making and some of the ways these mechanisms can go awry, what does this tell us

about whether we have free will, and how the legal system should deal with this?

Really, this breaks down into two, related questions. (1) Does the average human

have free will? (2) Does the average person who becomes involved with the legal

system have free will? A negative answer to either of these questions requires us to

revisit the strong assumptions of free will under which our legal system operates.

The second question is perhaps easier to address, as much of the research cited

above is directly pertinent to this question. Though it is by no means true that all

people who commit crimes are substance dependent or mentally ill, the fact that

substance abuse and mental illness plays a role in the behavior of a large percentage

of offenders is undeniable. To consider just one statistic on this relationship, the

Bureau of Justice Statistics reports that in 2002, 68% of jail inmates reported having

symptoms that satisfied the criteria for the DSM IV definition of substance

dependence during the year prior to their admission to jail (Substance Dependence,

Use, and Treatment of Jail Inmates, 2002). Our research has shown that substance

dependence is associated with impairment of the neural processes subserving

decision making and that this impairment is global (i.e., it applies to many decisions,

not only decisions about whether to engage in substance use) (Breiter, Aharon,

Kahneman, Dale, & Shizgal, 2001; Breiter & Rosen, 1999). Therefore, well over half

of people who are arrested and held in jails may be operating with an ability to decide

and exercise willpower that is lower than that of the average person.

It is important to note, however, that there is much more research that needs to be

done regarding the neuroscience of human decision making, and while substance

dependence is a relatively easy condition to identify and test it is only one example of

a neurological profile that results in decreased decision-making capacity. This point

is demonstrated by our recent work comparing the decision-making profiles of

inmates convicted of different criminal offenses with each other, and with the profiles

of normal controls, substance dependent subjects, and orbitofrontal cortex lesion

patients. We found that the profiles of individuals convicted of drug, sex, theft and

intoxicated driving offenses mirrored those of substance dependent subjects, while

the profiles of those convicted of assault and murder resembled the profiles of brain

lesion patients (Yechiam et al., 2006). The research revealed this pattern, but was

272 K. Burns and A. Bechara

not designed to assess why this result occurred, and thus leaves many questions open

for further study (e.g. At what point in the lives of these offenders did this profile

emerge? Due to what causes? What role did substance use by the offenders play in

creating these profiles? Why is it not then true that all brain lesion patients go on to

commit violent crimes? etc.). What is important to note for the purposes of this

article is that this pattern does exist, leaving us both with evidence that many more

people involved in the justice system may have gotten there operating with faulty

neural mechanisms, and that similar impairments may exist in other, as yet

unidentified, population subgroups that are also operating with less than full free will,

by any definition.

This understanding applies as well when we are talking about non-offender

populations: Can we say, knowing what we do about the neural mechanisms of

choice in healthy adults, that our choice is ‘‘free’’? As stated above, there are many

further avenues for research that will continue to teach us about the neuroscience of

willpower, and with those discoveries still in the future, we are reluctant to issue a

gross statement declaring that we do or do not have free will. Particularly relevant for

the issue of legal responsibility, more research could be done regarding the

decision-making processes in healthy individuals who are under stress, as is often the

case when choices that result in legal system involvement occur. We have focused

thus far on individuals who are across the board ‘‘normal’’, or who are subject to

conditions such as substance dependence or neurological disorder that affect them at

all times. A full understanding of the operation of the process of choice will include

the various states of mood, health and environment through which all human beings

cycle. As is the case in most disciplines, there is likely to be a continuum of

impairment in the exercise of willpower rather than a black-or-white state of

dysfunction or health.

This said, what we do know about the process of choice indicates that there is a

strong deterministic element to actions that appear to us to be indeterminist or freely

chosen. The exceptions, noted above, of impairments of willpower prove the rule

that our exercise of will, presumably in the service of being able to survive and thrive,

is influenced in large part by the automatic and involuntary functioning of particular

neural pathways. Recalling our discussion of the Iowa Gambling Task, lesion

patients who could accurately explain to researchers what a winning strategy for the

game was were nonetheless unable, due to neurological deficit, to follow that

strategy. This phenomenon demonstrates that it is more than an intellectual

understanding of consequences, morals and ethics that guides a person’s actual

behavior in the real world. It is also the operation of neural mechanisms that generate

somatic states, automatically and obligatorily, that exert enough of a bias on behavior

to render irrelevant the ability to ‘‘know’’ one should behave otherwise. What states

are actually generated depends on a complex network of all the stimuli a person has

ever encountered, all the responses she or he has ever had to those stimuli, and all the

brain patterns that these stimulus–response pairings have created.

Perhaps, then, the most important question is yet a third one: Do we possess the

kind of free will that justifies not only legal responsibility, but the stigma and

disapprobation that are associated with failures to conform to society’s laws? The

compassionate answer to this question must be no. How this might play out in a

reexamination of our societal assumptions is the subject of the next section of this

article.

Decision making and free will 273

LEGAL IMPLICATIONS OF THE NEUROSCIENCE OF DECISION MAKING: HOPES AND DIRECTIONS FOR

FUTURE INTERDISCIPLINARY RESEARCH

Before moving on, it is a good time to take note that although the examples we have

used so far, and on which we will continue to focus, come from criminal law,

decision-making research and what it reveals about free will has implications in many

areas of the law. Contract law, for example, is based on the premise that two or more

parties can decide upon a course of action and make commitments to each other to

follow rules of interaction that they set out for their relationship, and tort law’s

emphasis on duty and negligence presupposes some ability to control one’s behavior.

The criminal law example is perhaps particularly compelling because it is in criminal

law alone that the assumption of freedom of choice justifies relieving citizens of their

basic rights to liberty or even life. However, the call for society to view those who

break the law with understanding applies whether they violate criminal prohibitions,

contract provisions or duties of care to their fellow citizens.

Though courts embracing free will have done so because they have deemed it a

necessary assumption for an operable justice system, most scholars who have

addressed the issue have agreed that any scientific discoveries that undermine free

will do not therefore undermine all the foundations on which the criminal legal

system is based. Rather, they call for a reprioritization of values, better alignment

between the stated and actual reasons for the system’s character, or a commitment to

resolving some of the tensions that are already at play in the system and are only

highlighted, not created, by discoveries in the social and biological sciences (Cotton,

2005; Greene & Cohen, 2004; Jones, 2003). Examination of the four justifications

for punishment—deterrence, incapacitation, rehabilitation, and retribution—in

light of decision-making neuroscience lends further support to this way of

approaching the issue.

The Tenability of our Justifications for Punishment

Each of the four classic justifications for punishment expresses at least one facet of

the collection of interests that come into contact in the justice system. Since many of

these interests focus on theories of how to influence choice, or what is the correct

ethical response to bad choices that harm others, the research cited in this paper on

the neuroscience of choice has obvious implications for several of these justifications.

Indeed, rather than threatening the foundations of the system, it is our hope that the

research and its implications can be seen as a means to harmonize these justifications

into a more unified and workable whole by inspiring further research into the many

unanswered questions that remain to be answered as neuroscience researchers focus

more closely on forensic populations.

Retribution

The retributive impulse behind the features of the criminal justice system are

evident, if not in the facts of the system itself, then in the rhetoric of ‘‘tough on

274 K. Burns and A. Bechara

crime’’ political platforms and the ever-increasing harshness of proposed sentencing

and other criminal legislation. Some scholars credit retribution as being the primary

justification for punishment, as it is the one that best explains the actual features of

the system currently in operation (Greene & Cohen, 2004, pp. 1776–1777). Yet it is

perhaps the justification most undermined by any hypothesis of limited free will,

because who ‘‘deserves’’ punishment for the involuntarily action of neural

mechanisms?

Greene and Cohen provide a thorough analysis of this point in a recent article,

concluding that as advances in neuroscience reveal more about the mechanistic

nature of decision making, individuals in society will cling less firmly to their

retributive impulses and beliefs. Moreover, as more individual attitudes change, so

will the law. In their words, ‘‘The law will continue to punish misdeeds, as it must for

practical reasons, but the idea of distinguishing the truly, deeply guilty from those

who are merely victims of neuronal circumstances will, we submit, seem pointless’’

(Greene & Cohen, 2004, p. 1781). We believe that the decision-making processes

discussed in this article exemplify exactly the type of discovery to which Greene and

Cohen refer in their work, and that the implications are indeed as they predict.

That the ‘‘moral intuitions and commitments’’ (Greene & Cohen, 2004, p. 1778)

of society are changing in this way can be seen in the tensions that already exist in the

system as it is. Michelle Cotton, in another recent paper, outlines the historical

incursions determinism has made into the courtroom, driven by sympathies for those

who wind up in court due to behaviors that only make sense given their respective

mental developmental states (e.g. the mentally ill, youth, intoxicated persons). In

most areas, however, with some exceptions in juvenile law and the insanity defense, 1

Cotton contends that the fear of the slippery slope led courts and legislatures to

banish any vestiges of determinism from our practical philosophy of criminal

responsibility. The result is what she calls a ‘‘foolish consistency’’, which does not

take the realities of human psychology into account, and thus leaves us with a system

that neither inspires confidence nor achieves results (Cotton, 2005).

There is further tension between the sympathy that new understandings of human

behavior engender, and the retributive impulse that is not just a principle of law but is

itself a psychological phenomenon. Matthew Jones notes, in a piece discussing the

impact of genetics research on the law, that legal scholars ‘‘predicting the end to the

current criminal justice system are misguided . . . [because] they do not take into account the considerable role that punishment plays in acting as both a healing

device and an outlet for revenge’’ (Jones, 2003). Greene and Cohen, while

expressing optimism that society can learn to move past the retributive impulse, cite

recent primate studies demonstrating that revenge, or a sense of justice, might

inherently be with us from our evolutionary beginnings, presumably having aided the

survival of the species (Greene & Cohen, 2004). Thus while decision-making

1 For a good review of the difficulties in applying the insanity defense to defendants with frontal lobe dysfunction see the work of Seiden (2004). The author discusses the emphasis the Virginia insanity defense (which is similar to U.S. Supreme Court precedent and other state law) places on cognitive ability and moral sense/reasoning, which is not impaired in frontal lobe patients, and the resulting challenge in applying the defense to frontal lobe dysfunctional capital defendants. Similarly, an insanity defense is not the best way to address questions of free will in the law, as this defense is (and should be) designed to carve out a very small population of defendants, whereas we have argued that the questions for free will are not so easily limited.

Decision making and free will 275

research does give us cause to pull back on our legal system’s notion that we operate

with a will that is completely free, it is important to note that it has not addressed all

the biological processes that are behind the conflict between our retributive and our

altruistic natures.

What decision-making and other behavioral neuroscience research does allow us

to do, however, is to appreciate this tension scientifically. Guilt and innocence, fear

and revenge are principles that by their nature arouse emotions that make it

challenging for a society always to create the best solutions to the problems they fuel.

Perhaps by providing us with some healthy distance from these emotions, a

society-wide understanding of the neural mechanisms of will can contribute to a

more popular appreciation of the complexity of the notion of responsibility. We have

discussed the retribution justification first because the new temperance in exacting

retribution that neuroscience may inspire is important to keep in mind when

considering some of the shortcomings of the other three justifications.

Deterrence

The punitive system’s goals of deterrence require that people be able to act on the

prohibitions that the law defines, so an assumption of determinism may seem to

render this a futile aim. However, decision-making research reveals more than just a

disembodied mechanism of brain control. The mechanism we are discovering is one

that in healthy individuals is inextricably linked to the stimuli that historically have

existed in a person’s environment, which would of course include laws, experiences

of seeing the results of others violating laws or violating them oneself, and

experiences of learning moral lessons about the activities that are the subjects of the

laws. In other words, we are discovering one of the mechanisms by which deterrence

operates, over the long term of an individual’s neural development.

On the other hand, we have seen in the cases of impaired will that, nonetheless,

neurological conditions exist that result in people essentially ignoring experiences of

punishment. That the cognitive profile of violent offenders is so similar to that of

patients with just these conditions makes us wonder how, whether and to what

degree punishment is working as a deterrent with any particular person. Perhaps the

phenomenon of general deterrence (the deterrent effect that the possibility of

punishment has for society) accounts for more of the concept’s usefulness than does

specific deterrence (the deterrent effect that being punished has on a particular

offender). That is, in reforming our system, the biological foundations of the exercise

of will may favor a forward-looking focus on how our justice system impacts the

development of law-abiding behavioral patterns, over the more backward-looking,

retributive focus that currently exists. This and similar hypotheses deserve further

examination as decision-making research advances. The extremely high recidivism

rates we experience in the US speak for themselves as evidence that imprisonment

does not completely deter crime. In addition, the fact that criminal activity peaks in

the late teens and early 20s, and drops off in the 30s and 40s for the vast majority of

offenders, suggests the presence of additional deterrent factors that operate over

time. These factors may be predominantly environmental (either natural, such as

increased family responsibility, or imposed, as in punishments) or physiological (for

example, maturation of the prefrontal cortex, which continues into the 20s). Our

276 K. Burns and A. Bechara

hope is that decision-making research will shed light on what are the most effective

deterrents, and whether we can help their impact to be felt earlier in life.

Incapacitation

On the surface, the incapacitation justification is relatively unaffected by any

research regarding choice and will. It is a practical justification: People who commit

crimes need to be taken off of the streets, so that they are prevented from committing

more crimes. The decision process that led to the crime is not explicitly relevant.

However, the justification does rest to some degree on the assumption that there is a

type of person who ‘‘commits crimes’’, rather than a person who ‘‘happens to have

committed’’ a crime, and so is also interrelated with the final justification,

rehabilitation.

Rehabilitation

Decision-making research is a double-edged sword in a conversation about

rehabilitation. One the one hand, a deterministic view of the choice process seems to

undermine the very idea of rehabilitation. On the other, the more we understand the

brain, the greater our ability to design interventions that make the possibility of

rehabilitation real for many whom the law writes off today. For example, research

into the pharmacology of the different decision-making pathways indicates that the

pathways that operate using non-conscious knowledge work using the neuro-

transmitter dopamine, whereas conscious knowledge pathways make use of

serotonin (Bechara, Damasio, & Damasio, 2001). This discovery raises the

possibility of pharmacological interventions for individuals who suffer from chemical

imbalances interfering with their ability to make adaptive choices. Of course,

reversing the chemical deficiency is not enough; therapy that enables the relearning

of coping strategies in the presence of normal pharmacology is probably the most

effective treatment. More research is necessary into clinical applications of the

knowledge discussed in this article, which will create yet more rehabilitative

opportunity.

In discussing rehabilitative options, it is important to avoid pathologizing all

things related to choice, conflict and crime, a tendency that we find in our society as

psychological research advances in all areas. Moreover, discussion of rehabilitative

‘‘therapies’’ that are designed to effect how people exercise their will directly and

alarmingly raises ethical questions including the following. Who is making the

decision about what is a ‘‘good’’ exercise of will? Is the very notion of rehabilitation

paternalistic? How much autonomy will society grant to offenders, especially violent

offenders, in choosing not to submit to pharmacological or other intervention?

Adequate discussion of these questions is outside the scope of this article, but should

be foremost on our minds whenever we see the issues of free will and behavioral

modifications come together in any state-sponsored program. The issue of what to

do when offenders either cannot or do not want to be rehabilitated remains despite

what we learn from neuroscience, and should be considered in light of the

understandings we have gained about the other justifications for the criminal law

system.

Decision making and free will 277

CONCLUSION

Our exploration of the biology of human will and its implications for the legal system

has highlighted the complexity of the interaction between the two. Like the other

authors whose work we have cited, we are optimistic that society can embrace these

and other discoveries in the behavioral and social sciences as an opportunity for

creative reform rather than as a threat to our system’s foundations. The law often

changes slowly and conservatively, but we have already seen changes come in

response to new understandings of human behavior, and expect that this pattern will

only continue. Examples from the juvenile justice field demonstrate how this

evolution can work.

The juvenile system has throughout its existence been dealing with precisely the

questions that this article has been addressing about the extent to which our will is

free versus the extent to which our environment and constitution determines our

behavior. The separate juvenile system was in fact conceived with an understanding

of the determined nature of the behavior of youth (Cotton, 2005), and has

maintained this flavor notwithstanding punitive changes that have been made in

response to public fear of gang-involved youth. In recent years this characterization

has been buoyed by greater understanding of the course of brain development, and

the fact that even late in the teen years a person’s judgment abilities are limited

because the prefrontal cortex (exactly the area of the brain on which we have focused

so much attention here) is not fully developed until the early 20s. This is not to say

that the juvenile system is perfect; far from it: It suffers much from the unresolved

issues of will and determinism, which affect whether we conceptualize the juvenile

system as more criminal and punitive, or more civil and analogous to child welfare

systems. 2

We do, however, see a greater willingness to innovate in the juvenile system, which

likely is due to a corresponding willingness to release our retributive impulses,

knowing what we do about youth psychology. For example, there is a movement

toward introducing restorative justice models, based on the reconciliation

commissions that have been successful in conflict-torn regions, in our criminal

justice system, which has made some progress in the youth justice field. This model is

reflective, though perhaps unwittingly, of some of the brain science insights we

proposed above for the justifications of punishment. It is less harshly retributive,

viewing offenses instead as occurring in a social and psychological context. It is more

forward looking, as we suggested neurologically speaking might be a preferable way

to inspire deterrence, and is open to more creative and collaborative notions of

rehabilitation. Significantly, the Supreme Court also recently invalidated the juvenile

death penalty (Roper v. Simmons, 2005), in response to changing societal notions of

what are appropriate ways to deal with crime. These and other compassionate and

creative possibilities exist for making our legal system compatible with the evolving

definitions of responsibility, and better understandings of the neural mechanisms

2 See, for example, McKeiver v. Pennsylania (1971), a case in which the Supreme Court held that juveniles do not have the right to a trial by jury because of the differences between the juvenile and criminal system, reversing a trend toward granting juveniles in delinquency cases the constitutional protections afforded criminal defendants.

278 K. Burns and A. Bechara

underlying choice will hopefully inspire greater openness to such innovations for

juveniles as well as the adults they grow up to be.

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