John Mikhail - SSRN-Id762385
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Working Paper No. 762385
JOHN MIKHAIL
Investigating Intuitive Knowledge of the Prohibition of
Intentional Battery and the Principle of Double Effect
Aspects of the Theory of Moral Cognition:
Business, Economics and Regulatory Policy
Research Paper No. 762385
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John Mikhail, 2002All rights reserved
Aspects of the Theory of Moral Cognition:
Investigating Intuitive Knowledge of the Prohibition of Intentional Batteryand the Principle of Double Effect
John Mikhail1
Abstract: Where do our moral intuitions come from? Are they innate? Does the brain contain amodule specialized for moral judgment? Questions like these have been asked in one form oranother for centuries. In this paper, we take them up again, with the aim of clarifying them anddeveloping a specific proposal for how they can be empirically investigated. The paper presentsdata from six trolley problem studies of over five hundred individuals, including one group of
Chinese adults and one group of American children, which suggest that adults and children ages8-12 rely on intuitive or unconscious knowledge of specific moral principles to determine the
permissibility of actions that require harming one person in order to prevent harm to others.Significantly, the knowledge in question appears to be merely tacit: when asked to explain or
justify their judgments, experimental subjects were consistently incapable of articulating theoperative principles on which their judgments appear to have been based. We explain thesefindings with reference to an analogy to human linguistic competence. Just as normal personsare typically unaware of the principles guiding their linguistic intuitions, so too are they oftenunaware of the principles guiding their moral intuitions. These studies pave the way for futureresearch by raising the possibility that specific poverty of the stimulus arguments can beformulated in the moral domain. Differences between our approach to moral cognition and those
of Piaget (1932), Kohlberg (1981), and Greene et al. (2001) are also discussed.
1. Introduction
Where do our moral intuitions come from? Are they innate? Does the brain contain a
module specialized for moral judgment? Does the human genetic program contain instructions
for the acquisition of a sense of justice or moral sense? Questions like these have been asked in
one form or another for centuries. In this paper we take them up again, with the aim of clarifying
them and developing a specific proposal for how they can be empirically investigated.
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In Section 1, we summarize our approach to the theory of moral cognition and explain
some basic elements of our theoretical framework. We also introduce examples of the
perceptual stimuli used in our research and discuss some of the properties of the moral intuitions
they elicit. In Sections 2-7, we present the results of six trolley problem studies designed to
investigate the moral competence of adults and of children ages 8-12 in particular, their intuitive
or unconscious knowledge of the prohibition of intentional battery and the principle of double
effect. In Section 8, we provide a general discussion of our findings and contrast our approach to
moral cognition with those of Piaget (1932/1965), Kohlberg (1981), and Greene, Sommerville,
Nystrom, Darley & Cohen (2001). Section 9 is an Appendix containing both the stimulus
materials used in our experiments and our subjects responses to them.
1.1 Theoretical Framework
Like many theorists, we begin from the assumption that the theory of moral cognition
may be usefully modeled on aspects of the theory of linguistic competence (see, e.g., Chomsky,
1978 Cosmides & Tooby, 1994 Dwyer, 1999 Goldman, 1993 Harman, 2000 Mahlmann,
1999 Mikhail, 2000 Mikhail, Sorrentino & Spelke, 1998 Rawls, 1971 Stich, 1993). Our
research is thus organized, in the first instance, around three questions, close analogues of the
fundamental questions in Chomskys (1986) framework for the investigation of human language.
(1) (a) What constitutes moral knowledge?(b) How is moral knowledge acquired?(c) How is moral knowledge put to use?
A brief overview of some of the concepts and terminology we use to clarify these
questions may be helpful. In our framework, the answer to (1a) is given by a particularmoral
grammaror theory ofmoral competence: a theory of the mind/brain of a person who possesses a
system of moral knowledge, or what might be referred to informally as a moral faculty, moral
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sense or conscience. The answer to (1b) is given by Universal Moral Grammar(UMG): a
theory of the initial state of the moral facultywhich, in keeping with conventional assumptions
of modularity (see, e.g., Fodor, 1983 Gazzaniga, 1992 Gazzaniga, Ivry & Magnum, 1998
Pinker, 1997), we provisionally assume to be a distinct subsystem of the mind/brainalong with
an account of how the properties UMG postulates interact with experience to yield a mature
system of moral knowledge. The answer to (1c) is given by a theory ofmoral performance: a
theory of how moral knowledge enters into the actual representation and evaluation of human
acts and institutional arrangements, as well as other forms of actual conduct (see, e.g., Dwyer,
1999 Mikhail, 2000 compare Rawls, 1971 Nozick, 1968).
Following Chomsky (1965), we use the terms observational adequacy, descriptive
adequacy and explanatory adequacy to refer to increasing levels of empirical success a theory
of moral cognition might achieve. A moral theory is observationally adequate with respect to a
given set of moral judgments to the extent that it provides a correct description of those judgments
in some manner or other, for example, by listing them or by explicitly stating a set of principles
from which they can be derived. A moral theory is descriptively adequate with respect to the
mature individuals moral competence to the extent that it correctly describes that system, in other
words, to the extent it provides a correct answer to (1a). Finally, a moral theory meets the
condition ofexplanatory adequacy to the extent it correctly describes the initial state of the moral
faculty and correctly explains how the properties of the initial state it postulates interact with
experience to yield a mature system of moral competence in other words, to the extent that it
provides a correct answer to (1b) (Mikhail, 2000).2
Unlike Kohlberg (1981), we distinguish sharply between an individuals operative moral
principles (those principles actually operative in her exercise of moral judgment) and herexpress
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principles (those statements she makes in the attempt to describe, explain, or justify her
judgments). We make no assumption that the normal individual is aware of the operative
principles which constitute her moral knowledge, or that she can become aware of them through
introspection, or that her statements about them are necessarily accurate. On the contrary, we
hypothesize that just as normal persons are typically unaware of the principles guiding their
linguistic or visual intuitions, so too are they often unaware of the principles guiding their moral
intuitions. In any event, the important point is that, as with language or vision, the theory of moral
cognition must attempt to specify what the properties of moral competence actually are, not what a
person may report about them (Haidt, 2001 Mikhail, 2000 Mikhail, Sorrentino & Spelke, 1998).
Finally, we follow Chomsky (1995), Lewontin (1990), Marr (1982), and other
commentators in assuming that the problems of descriptive and explanatory adequacy possess a
certain logical and methodological priority over more complicated inquiries into the neurological
and evolutionary foundations of moral cognition and behavior. Hence we carefully distinguish
(1a)-(1c) from two further questions a complete theory of moral cognition must answer:
(1) (d) How is moral knowledge physically realized in the brain?(e) How did moral knowledge evolve in the species?
Although many researchers have addressed questions like these, their efforts seem at this
juncture to be somewhat premature. Just as our ability to ask well-focused questions about the
evolution and physical bases of language depends on solving the problems of descriptive and
explanatory adequacy in the linguistic domain (Chomsky, 1995 Hauser, Chomsky & Fitch,
2002), so too is our understanding of (1d) and (1e) advanced by achieving reasonably correct
solutions to questions like (1a) and (1b) in the moral domain. Put simply, we cannot profitably
ask how moral knowledge evolved in the species or where it resides in the brain until what
constitutes moral knowledge and how it is acquired are better understood.
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1.2 Perceptual Stimuli and Perceptual Model
Research in the Piagetian tradition has attempted to answer questions like (1a) and (1b)
by investigating the developing childs mental representations of the subjective and
objective elements of moral judgment, the former consisting of the goals and intentions of an
action, the latter consisting of an actions effects and material consequences. In Piagets
(1932/1965) original studies, children were found to base their moral judgments on mental
representations of effects, not intentions, until around age nine. More recently, many
investigators have suggested that these findings were an artifact of the methods and assessment
procedures Piaget employed. Some researchers (e.g., Baird, 2001 Berndt & Berndt, 1975
Costanzo, Coie, Grumet & Farnhill, 1973 Lilliard & Flavell, 1990 Nelson, 1980) have
discovered that children as young as three use information about motives and intentions when
making moral judgments, if that information is made explicit and salient. Moreover, a
considerable body of research on infant cognition (e.g., Gergely, Nadasdy, Csibra & Biro, 1995
Johnson, 2000 Meltzoff, 1995 Woodward, Sommerville & Guajardo, 2001) suggests that even
young infants are predisposed to interpret the actions of animate agents in terms of their goals
and intentions.
Our research seeks to build on these prior studies by investigating how experimental
subjects reconstruct and utilize information about intentions and effects when evaluating
morally complex acts that is, acts and omissions which are comprised of multiple intentions
and which generate both good and bad effects. To illustrate, consider the following examples of
the so-called trolley problem and related thought experiments invented by Foot (1967) and
Thomson (1985).
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The Trolley ProblemCharlie is driving a train when the brakes fail. Ahead five people are working onthe track with their backs turned. Fortunately, Charlie can switch to a side track, if he actsat once. Unfortunately, there is also someone on that track with his back turned. IfCharlie switches his train to the side track, he will kill one person. If Charlie does not
switch his train, he will kill five people.
Is it morally permissible for Charlie to switch his train to the side track?
The Transplant ProblemDr. Brown has five patients in the hospital who are dying. Each patient needs a neworgan in order to survive. One patient needs a new heart. Two patients need a newkidney. And two more patients need a new lung. Dr. Brown can save all five patients ifhe takes a single healthy person and removes her heart, kidneys, and lungs to give tothese five patients. Just such a healthy person is in Room 306. She is in the hospital forroutine tests. Having seen her test results, Dr. Brown knows that she is perfectly healthy
and of the right tissue compatibility. If Dr. Brown cuts up the person in Room 306 andgives her organs to the other five patients, he will save the other five patients, but kill theperson in Room 306 in the process. If Dr. Brown does not cut up the person in Room306, the other five patients will die.
Is it morally permissible for Dr. Brown to cut up the person in Room 306?
The Bystander ProblemEdward is taking his daily walk near the train tracks when he notices that the train that isapproaching is out of control. Edward sees what has happened: the train driver saw fiveworkmen men ahead on the tracks and slammed on the brakes, but the brakes failed andthe driver fainted. The train is now rushing toward the five men the banks are so steepthat they will not be able to get off the track in time. Fortunately, Edward is standingnext to a switch, which he can throw, that will turn the train onto a side-track.Unfortunately, there is one person standing on the side-track, with his back turned.Edward can throw the switch, killing the one or he can refrain from doing this, letting thefive die.
Is it morally permissible for Edward to throw the switch?
The Footbridge ProblemNancy is taking her daily walk near the train tracks when she notices that the train that isapproaching is out of control. Five men are walking across the tracks. The train is movingso fast that they will not be able to get off the track in time. Nancy is standing next to aman, whom she can throw in front of the train, thereby preventing it from killing the men.
Nancy can throw the man, killing him but saving the five men or she can refrain fromdoing this, letting the five die.
Is it morally permissible for Nancy to throw the man?
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As we discuss below, when experimental subjects were presented with these scenarios,
they judged Charlies turning the train in The Trolley Problem to be permissible, Dr. Browns
cutting up the patient in the Transplant Problem to be impermissible, Edwards throwing the
switch in the Bystander Problem to be permissible, and Nancys throwing the man in the
Footbridge Problem to be impermissible (Table 1). These responses confront us with a
potentially surprising contrast between the Trolley and Bystander Problems, on the one hand,
and the Transplant and Footbridge Problems, on the other. In the former problems, saving five
people at the cost of killing one person is thought to be permissible. In the latter problems, by
contrast, saving five at the cost of killing one is held to be impermissible.
Table 1: Moral Intuitions of Trolley, Transplant, Bystander, and Footbridge ProblemsProblem Action Good Effect Bad Effect Deontic
StatusTrolley Charlies turning the train Preventing 5 deaths 1 Death Permissible
Transplant Dr. Browns cutting up the patient Preventing 5 deaths 1 Death Impermissible
Bystander Edwards throwing the switch Preventing 5 deaths 1 Death Permissible
Footbridge Nancys throwing the man Preventing 5 deaths 1 Death Impermissible
These facts lead us to speculate about the cognitive mechanisms the mind employs in
responding to these four scenarios. In the first instance, they lead us to ask the following
question: what are the operative principles of moral competence that are responsible for these
divergent responses? The problem is more difficult than it may seem at first. On the one hand,
comparatively simple deontological and consequentialist moral principles (e.g., If an act causes
death, then it is wrong, If the consequences of an act are better than the consequences of any of
available alternative, then it is required, etc.) are incapable of explaining the pattern of
intuitions elicited by these problems. For example, a simple deontological principle forbidding
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all killing would generate the intuition that Charlies switching tracks in the Trolley Problem and
Edwards switching tracks in the Bystander Problem are impermissible. But these actions are
judged to be permissible. Likewise, a simple utilitarian principle requiring agents to perform
actions with the best foreseeable consequences would presumably generate the intuition that Dr.
Browns cutting up the patient in the Transplant Problem and Nancys throwing the man in the
Footbridge Problem are obligatory, or at least permissible yet these actions are judged to be
impermissible.
On the other hand, conditional principles whose antecedents simply restate those action-
descriptions found in the stimulus (e.g., If an act is of the type throwing the switch, then it is
permissible If an act is of the type throwing the man then it is impermissible,) are also
descriptively inadequate. This is because they lead us to make inaccurate predictions of how
these action-descriptions will be evaluated when they are embedded in materially different
circumstances. For example, as we discuss below, when the costs and benefits in the Bystander
Problem are manipulated, so that an action described as throwing the switch will save $5
million of equipment at the cost of killing one person, individuals judge the action so described
to be impermissible. Likewise, when the circumstances of the Footbridge Problem are modified
so that the action described as throwing the man is presumed to involve consensual touching,
subjects judge the action to be permissible. In general, it is easy to show that the action-
descriptions used in these problems are morally neutral (Baird, 2001 Nelson, 1980), in the
sense that the permissibility judgments they elicit are circumstance-dependent.
Since the circumstances of an action can vary along an indefinite number of dimensions
(e.g., DArcy, 1963 Donagan, 1977 Lyons, 1965 Stone, 1964), the conclusion to which we
quickly are led by considerations like these is that any attempt to explain the moral intuitions
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elicited by these examples by means of a simple stimulus-response model is doomed at the start.
Although each of these moral intuitions is occasionedby an identifiable stimulus, how the mind
goes about interpreting these hypothetical fact patterns, and separating the actions they depict
into those that are permissible and those that are not, is not something revealed in any obvious
way by the surface properties of the stimulus itself. Instead, an intervening step between
stimulus and response must be postulated: a pattern of organization of some sort that is imposed
on the stimulus by the mind itself. Hence a simple perceptual model such as the one in Figure 1
is inadequate for explaining these moral intuitions. Instead, as is the case with language
perception (Chomsky, 1964), an adequate perceptual model must, at a minimum, look more like
the one in Figure 2.
Fig. 1: Simple Perceptual Model for Moral Judgment
INPUT ?
PERMISSIBLE
IMPERMISSIBLE
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?
PERMISSIBLE
IMPERMISSIBLE
STRUCTURAL
DESCRIPTION
Perceptual
Response:
Moral
Judgment
Unconscious
Mental
Representation
INPUT ?
Conversion
RulesStimulus:
Fact Pattern
Deontic Rule s
Fig. 2: Expanded Perceptual Model for Moral Judgment
The expanded perceptual model in Figure 2 implies that, like grammaticality judgments,
permissibility judgments do not necessarily depend on the surface properties of an act ion-
description, but on more fundamental properties of how that action is mentally represented. Put
differently, it suggests that the problem of descriptive adequacy in the theory of moral cognition
may be divided into at least two parts: (a) the problem of determining the nature of the
computational principles (i.e., deontic rules) operative in the exercise of moral judgment, and
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(b) the problem of determining the representational structures (i.e., structural descriptions)
over which those computational operations are defined.
What are the properties of these intervening mental representations? In our view, it
seems reasonable to suppose that morally cognizable fact patterns are mentally represented in
terms of abstract categories like act, consequence, and circumstance agency, motive, and
intention proximate and remote causes and other familiar concepts that are the stock in trade of
philosophers, lawyers, and jurists (Mikhail, 2000 see also Donagan, 1977 Sidgwick, 1907). But
which specific concepts does the system of moral cognition in fact use? In what manner, i.e.,
according to what principles or rules, does it use them? Answers to questions like these, if
available, would begin to solve the problem of descriptive adequacy.
1.3 Our Hypothesis
Our hypothesis is that the moral intuitions generated by the Trolley, Transplant, Bystander,
and Footbridge problems and structurally similar thought experiments (henceforth, trolley
problems) can be best explained by postulating intuitive knowledge of specific moral principles,
including the prohibition of intentional battery and the principle of double effect. The former is
a familiar principle of both common morality and the common law proscribing acts of
unpermitted, unprivileged bodily contact, that is, of touching without consent (Prosser, 1941
Shapo, 2003). The latter is a complex principle of justification, narrower in scope than the
traditional necessity or choice of evils defense, which in its standard formulation holds that an
otherwise prohibited action may be permissible if the act itself is not wrong, the good but not the
bad effects are intended, the good effects outweigh the bad effects, and no morally preferable
alternative is available (Mikhail, 2000 see also Fischer & Ravizza, 1992). Both of these
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principles require clarification, but taken together and suitably elaborated they can be invoked to
explain the relevant pattern of intuitions in a relatively simple and straightforward manner. The
key structural difference between the two sets of examples is that, in Transplant and Footbridge
problems, the agent commits a series of distinct trespasses prior to and as a means of achieving
his good end, whereas in the Trolley and Bystander problems, these violations are subsequent
and foreseen side effects. Figures 3 and 4 illustrate this difference in the case of the Footbridge
and Bystander problems.
Ds throwing the man at t(0)
Ds committing battery at t(0)
Ds preventing the trainfrom killing the men at t
(+n+o)
Ds killing the man
at t(+n+p)
Ds causing the trainto hit the man at t
(+n)
Ds committing battery at t(+n)
Fig. 3: Mental Representation of Footbridge Problem
Side
Effects
End
Means
Ds committing
homicide at t(+n+p)
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Our computational hypothesis holds that when people encounter the Footbridge and
Bystander problems, they spontaneously compute unconscious representations like those in
Figures 3 and 4.3 Note that in addition to explaining the relevant intuitions, this hypothesis has
further testable implications. For example, we can investigate the structural properties of the
underlying representations by asking subjects to evaluate certain probative descriptions of the
relevant actions. Descriptions using the word by to connect individual nodes of the tree in the
downward direction (e.g., D turned the train by throwing the switch, D killed the man by
turning the train) will be deemed acceptable by contrast, causal reversals using by to connect
nodes in the upward direction (D threw the switch by turning the train, D turned the train by
killing the man) will be deemed unacceptable. Likewise, descriptions using the phrase in order
to to connect nodes in the upward direction along the vertical chain of means and ends (D
Ds throwing the switch at t(0)
Ds turning the train at t(+n)
Ds preventing the train
from killing the men at t(+n)
Ds causing the train
to hit the man at t(+n+o)
Ds committing battery
at t(+n+o)
End
Fig. 4: Mental Representation of Bystander Problem
Side Effects
Ds killing the man
at t(+n+o+p)
Ds committing
homicide at t(+n+o+p)
Means
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threw the switch in order to turn the train) will be deemed acceptable. By contrast, descriptions
of this type linking means with side effects (D threw the switch in order to kill the man) will
be deemed unacceptable. In short, there is an implicit geometry to these representations, which
an adequate theory can and must account for.
Our hypothesis is interesting and controversial for several reasons. First, while many
theorists have suggested that the principle of double effect may be part of a descriptively
adequate theory of trolley intuitions (e.g., Harman, 1977, 2000), and of human morality
generally (e.g., Nagel, 1986 Quinn, 1993), no prior experimental studies have directly tested this
assumption. The experiments by Petrinovich and his colleagues (Petrinovich & ONeill, 1996
Petrinovich, ONeill & Jorgensen, 1993), which utilize trolley problems, do not adequately
clarify this issue, because of their focus on behavioral predictions (e.g., asking participants to
answer the question What would you do?) rather than on deontic judgments per se (e.g., asking
participants to answer the question Is X morally permissible?). Likewise, Greene et al. (2001),
who also use trolley problems as probes, also appear to leave this issue unresolved (see 8.2.3).
Second, our hypothesis is significant because, if it is true, it implies that the mental
operations involved in the exercise of moral judgment are more complex than is commonly
thought. For the principle of double effect, for example, to be operative in its standard
formulation, adults and children must possess a list of intrinsically wrong acts, a set of rules for
generating morally cognizable act-representations, and a calculus of some sort for computing
and comparing the probabilities ofan actions good and bad effects. They must also have the
cognitive resources to distinguish the act itself from its effects and further consequences, to
distinguish the acts foreseen effects from its intended effects, and, more generally, to
differentiate the acts causal and intentional properties from those of its alternatives. Further,
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they must compute act-representations in terms of properties like ends, means, and side effects,
even though the stimulus contains no direct evidence of these properties. In short, our
hypothesis implies that ordinary peoplenot just trained lawyers or philosopherspossess a
complex sense of justice that incorporates subtle elements of a fully articulated legal code,
including abstract theories of causation and intention.
Finally, our hypothesis raises interesting and novel questions for the theory of moral
development. Specifically, it leads us to ask whether children are explicitly taught the principle
of double effect, and if not, whether the principle or some variant of it is in some sense innate.
As Harman (2000) explains, this question naturally arises as soon as one settles on an
explanation of the structure of our moral intuitions that makes reference to this principle. An
ordinary person was never taught the principle of double effect, Harman observes, and it is
unclear how such a principle might have been acquired by the examples available to the ordinary
person. This suggests that [it] is built into . . . morality ahead of time (Harman, 2000, p. 225).
Similar reasoning may be thought to apply to the prohibition of intentional battery, at least as
that prohibition is defined and utilized here.4 On reflection, it seems doubtful that children are
affirmatively taught to generate the specific representations presupposed by this principle to any
significant extent. We thus seem faced with the possibility that certain moral principles emerge
and become operative in the exercise of moral judgment that are neither explicitly taught, nor
derivable in any obvious way from the data of sensory experience. In short, we appear
confronted with an example of what Chomsky calls the phenomenon of the poverty of the
stimulus in the moral domain (Dwyer, 1999 Mikhail, 2000 compare Chomsky, 1986).
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CHILDS
LINGUISTIC
DATA
LINGUISTIC
GRAMMAR
CHILDS
MORAL
DATA
MORAL
GRAMMAR
EnglishJapanese
Zapotec
Malagasy
Arabic
How much diversity?
UG
UMG
?
?
Figure 5: Acquisition Models for Language and Morality
The argument from the poverty of the moral stimulus (Mikhail, 2000) can be depicted
graphically by means of an acquisition model similar to the one Chomsky (1964) initially proposed
in the case of language (Figure 5). In the linguistic version of this model, Universal Grammar
(UG) may be regarded as a theory of innate mechanisms, an underlying biological matrix that
provides a framework within which the growth of language proceeds, and proposed principles of
UG may be regarded as an abstract partial specification of the genetic program that enables the
child to interpret certain events as linguistic experience and to construct a system of rules and
principles on the basis of that experience (Chomsky, 1980, p. 187). Likewise, in the case of
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moral development, Universal Moral Grammar (UMG) may be regarded as a theory of innate
mechanisms that provides the basic framework in which the development of moral competence
unfolds, and specific principles of UMG may be regarded as a partial characterization the innate
function that maps the developing childs relevant moral experience (her moral data) into the
mature state of her acquired moral competence (i.e., her moral grammar).
The linguistic grammars children acquire are hopelessly underdetermined by the data
available to them as language learners linguists therefore postulate a significant amount of innate
knowledge to fill this gap (e.g., Baker, 2001 Pinker, 1994). Further, because every normal human
child can and will learn any of the worlds natural languages simply by being placed in an
appropriate environment, UG must be rich and specific enough to get the child over the learning
hump, but not so specific as to preclude her ability to acquire every human language (Chomsky,
1986). Turning to UMG, it is unclear whether a similar situation and a similar tension between
descriptive and explanatory adequacy obtains. Nevertheless, the acquisition model we have
sketched, though abstract, can be made more concrete by considering the specific example of
trolley intuitions. If a computational moral grammar does in fact enter into the best explanation of
these intuitions, then two further questions arise within the framework of this model: First, what
are the properties of the moral grammars that people do in fact acquire, and how diverse are they?
Second, what informational gaps, if any, can be detected between the inputs and outputs of the
model? That is, what if any principles of moral grammar are acquired for which the environment
contains little or no evidence? According to the argument from the poverty of the moral stimulus,
if specific principles emerge and become operative in the course of normal moral development,
but the acquisition of these principles cannot be explained on the basis of the childs moral data,
then the best explanation of how children acquire these principles may be that they are innate, in
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Chomskys dispositional sense (Chomsky, 1986 see also Baker, 2001 Dwyer, 1999 Mikhail
2002 Pinker, 1994 Spelke, 1998).
2. Experiment 1
Having introduced some elements of our theoretical framework, we turn directly to a
discussion and analysis of our experimental findings. At the outset of our investigations, we
were interested in a variety of questions that might be asked about thought experiments like the
trolley problems and the moral intuitions they elicit, including the following: First, are these
intuitions widely shared? Are they shared across familiar demographic categories like gender,
race, nationality, age, culture, religion, or level of formal education? Second, what are the
operative principles? How precisely can we characterize the relevant mental operations and to
what extent are they open to conscious introspection? Third, how are the operative principles
learned or acquired? What might examples like these eventually tell us about moral
development and the acquisition of the moral sense?
Our first study attempted to address only a subset of these questions, including (1)
whether and to what extent these intuitions are widely shared (2) what are the operative
principles and (3) whether the operative principles are open to conscious introspection.
2.1 Method
2.1.1 Participants
Participants were 40 adult volunteers from the M.I.T. community between the ages of 18-
35. The group consisted of 19 women and 21 men.
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2.1.2 Stimuli and Procedure
Eight scenarios were used, all of which were adapted from Foot (1967), Thomson (1986),
and Harman (1977) (see 9 for the complete text of these scenarios see also Mikhail, 2000). In
all eight scenarios, an agent must choose whether to perform an action that will result in one
person being killed and five other persons, who would otherwise die, being saved.
The scenarios were divided according to our hypothesis into two groups. Four scenarios,
which were modeled on the Transplant and Footbridge Problems, described a choice between (a)
committing an intentional battery in order to prevent five other people from dying, knowing that
the battery will also constitute a foreseeable but non-intentional homicide, and (b) refraining
from doing so, thereby letting the five die. Four other scenarios, which were modeled on the
Trolley and Bystander Problems, described a choice between (a) doing something in order to
prevent five people from dying, knowing that the action will constitute a foreseeable but non-
intentional battery and a foreseeable but non-intentional homicide, and (b) refraining from doing
so, thereby letting the five die.
The morally salient difference between the two sets of cases, in other words, concerned
the type of battery embedded in the agents action plan. In the first group of scenarios, the
battery was intentional, embedded within the agents action plan as a means (henceforth
Intentional Battery). In the second group, the battery was foreseeable (but not intentional),
embedded within the agents action plan as a side effect (henceforth Foreseeable Battery).
Each participant received a written questionnaire containing one scenario. The
participant was first instructed to read the scenario and to judge whether or not the proposed
action it described was morally permissible. The participant was then asked on a separate page
of the questionnaire to provide reasons explaining or justifying his or her response. Twenty
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participants were given an Intentional Battery scenario. The other twenty participants were
given a Foreseeable Battery scenario. The assignment of participants to scenario type was
random.
2.2 Results
2.2.1 Judgments
The main results of Experiment 1 are presented in Figure 6. 2 of 20 participants in the
Intentional Battery condition judged the action constituting intentional battery to be permissible.
By contrast, 19 of 20 participants in the Foreseeable Battery condition scenario judged the action
constituting foreseeable battery to be permissible. This difference is significant: x2 (1, N=40) =
28.96, p < .001, suggesting that the scenarios evoke different action representations whose
properties are morally salient.5
Male and female responses in Experiment 1 are presented in Figure 7. Of the 10 men
given an Intentional Battery scenario, 2 judged the action constituting intentional battery to be
permissible and 8 judged it to be impermissible. Of the 10 women given an Intentional Battery
scenario, all 10 judged the action constituting intentional battery to be impermissible.
Meanwhile, all 11 of the men and 8 of the 9 women who were given a Foreseeable Battery
scenario judged the action constituting foreseeable battery to be permissible. These differences
are also significant, x2 (1, N=19) = 15.44, p < .001 (women) and x2 (1, N=21) = 14.6, p < .001
(men), suggesting that there are no significant gender differences in the way the two types of
scenario are mentally represented and morally evaluated.
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0
2
4
6
8
10
12
14
16
18
20
Intentional
Battery
Foreseeable
Battery
Permiss.
Impermiss.
Act Type
Subjects
Figure 6: Moral Judgments of Two Act Types in Experiment 1
(Intentional Battery vs. Foreseeable Battery)
X2 (1, N=40) = 29.0,
p < .001
0
2
4
6
8
10
12
Men Women Men Women
Permiss.
Impermiss.
Intentional
Battery
Subjects
Figure 7: Judgments of Act Types in Experiment 1 by Gender
(Intentional Battery vs. Foreseeable Battery)
Foreseeable
Battery
X2 (1, N=19) = 15.44,
p < .001 (women).
X2 (1, N=21) = 14.6,
p < .001 (men).
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2.2.2 Justifications
Subjects expressed principlesthe responses they provided to justify or explain their
judgmentswere also coded and analyzed. Three categories of increasing adequacy were used
to classify these responses: (1) no justification, (2) logically inadequate justification, and (3)
logically adequate justification. Responses that were left completely blank were categorized
under the heading of no justification. Responses that were not blank but which failed to state a
reason, rule, or principleor to identify any feature whatsoever of the given scenariothat
could in principle generate the corresponding judgment were classified as logically inadequate
justifications. Finally, responses that did state a reason, rule, or principle, or did otherwise
identify at least one feature of the given scenarioeven one that was obviously immaterial,
irrelevant, arbitrary, or ad hocthat could in principle generate the corresponding judgment
were classified as logically adequate justifications.
Utilizing this taxonomy, two researchers independently coded a subset of justifications
and achieved an inter-observer reliability of 89% (n=36). One researcher then coded the
complete set of justifications collected in Experiment 1. 32.5% (13/40) of participants gave no
justification, 17% (7/40) provided logically inadequate justifications, while only 50% (20/40)
provided logically adequate justifications. Furthermore, many of the logically adequate
justifications consisted of simple deontological or consequentialist principles that were evidently
incapable of generating the conflicting pattern of intuitions in Experiment 1. These justifications
thus failed the test of observational adequacy in the sense defined in 1.1. These findings
together with the data on expressed justifications gathered in our remaining studies are discussed
again in 8.
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2.3 Discussion
Experiment 1 was designed to achieve several different objectives. First, it was meant to
investigate a set of untested empirical claims implicit in the philosophical and legal literature
about how the trolley problems are mentally represented and morally evaluated. In their
accounts of trolley problems, philosophers and legal theorists often take for granted the deontic
status readers will assign to a given action sequence (e.g., Fischer & Ravizza, 1992 Katz, 1987
Thomson, 1985). Prior to our studies, however, no controlled experiments had directly tested
these assumptions or attempted to extend them to broader populations. Instead, prior
experimental research using trolley problems as probes (Petrinovich & ONeill, 1996
Petrinovich et al., 1993) had left these issues largely unresolved. As we predicted, conventional
assumptions about the deontic intuitions elicited by these problems were confirmed, and the
intuitions themselves were widely shared.
Second, Experiment 1 was designed to investigate whether the participants in our
experiments could, when asked, provide coherent and well-articulated justifications for their
judgments about individual trolley problems. Based on informal observation, as well as theory-
dependent considerations arising from the linguistic analogyin particular, the inaccessible
status of principles of grammarwe predicted that many or most of our subjects be incapable of
doing so. This prediction also held: even under an extremely liberal coding scheme, according to
which a justification was deemed logically adequate if it picked out at least one distinguishing
feature of the given scenario, even one that was obviously immaterial, irrelevant, arbitrary, or ad
hoc, that could in principle serve as part of the premises of an argument that arrives at the
matching judgments (Rawls, 1971, p. 46), only 50% of the participants in our study provided
logically adequate justifications for their judgments. Additionally, as indicated, many of these
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justifications were inadequate to account for the pattern of intuitions generated in Experiment 1
and thus failed the test of observational adequacy in the sense defined in 1.1. This suggested
that a within-subject design would elicit considerable fewer logically adequate justifications than
a between-subject design, because in the former condition subjects would be required to
reconcile and explain two contrary intuitions by means of an overarching rationale or principle.
On this basis, we decided to utilize a within-subject design in Experiment 2 (see 3).
A further objective of Experiment 1 was to investigate our hypothesis that the moral
intuitions generated by the trolley problems could be explained by postulating intuitive
knowledge of the prohibition of intentional battery and the principle of double effect. As
interpreted here, the combined effect of mechanically applying these principles to these scenarios
would be to permit throwing the switch and turning the train in the Trolley and Bystander
conditions but to prohibit cutting up the patient and throwing the man in the Transplant and
Footbridge conditions. This is how participants did, in fact, respond in these conditions, thus
confirming to a limited extent our hypothesis about operative principles.
Finally, Experiment 1 was also meant to begin the process of investigating the potential
universality of a certain class of moral intuitions, such as those elicited by the trolley problems,
by determining whether one sample of adult men and women would share intuitive responses to
these problems. Again, based upon informal observation, as well as various theory-dependent
considerations (Mikhail, 2000), we predicted that there would be no statistically significant
gender differences. This prediction also helda finding that is at least potentially in conflict
with the claims of Gilligan (1982) and others that men and women typically differ in how they
evaluate moral problems.
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In sum, the findings of Experiment 1 constitute evidence that one component of moral
knowledge, deontic knowledge, consists of a system of rules or principles (a moral grammar)
capable of generating and relating mental representations of various elements of an action plan
(Mikhail et al., 1998). Our findings also constitute evidence that the moral grammar contains
principles capable of distinguishing intentional battery (battery embedded within an agents
action plan as a means) and foreseeable battery (battery embedded within an agents action plan
as a side effect), as well as a further principle, such as the principle of double effect or some
comparably complex ordering principle (Donagan, 1977), prohibiting intentional battery but
permitting foreseeable battery in the context of cases of necessity such as the trolley problems.
Because subjects displayed only a limited ability to provide adequate justifications of their
intuitions, Experiment 1 also implies that, as is the case with linguistic intuitions, the principles
generating moral intuitions are at least partly inaccessible to conscious introspection. Finally,
our findings also suggest that at least some moral intuitions are widely shared, irrespective of
gender.
3. Experiment 2
In Experiment 1, we discovered an apparent difference between the way intentional
battery and foreseeable battery are mentally represented and morally evaluated, at least in the
context of cases of necessity such as the trolley problems. We also discovered that the moral
competence of both men and women appears to consist, at least in part, of intuitive or
unconscious knowledge of the prohibition of intentional battery and the principle of double
effect. Experiment 2 was designed to bring additional evidence to bear on these hypotheses, in
three different ways.
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The first way was to investigate the concept of battery that was used in our analysis of
Experiment 1. In Experiment 1, we drew on established legal doctrine in assuming that battery
could in effect be defined as unpermitted or unprivileged contact with a person, that is, as
contact without consent (Prosser, 1941 Shapo, 2003). Moreover, we followed the traditional
law of tort in assuming that the notion of unprivileged contact extends to any part of the body,
or to anything which is attached to it and includes any touching of one person by another or by
any substance put in motion by him (Hilliard, 1859). In Experiment 2, we investigated this
concept of battery by modifying one of the Intentional Battery scenarios used in Experiment 1,
so that an action described as throwing the man, which previously constituted battery, no
longer did so, because under the modified circumstances the action would likely be represented
as consensual. We did this by constructing a scenario in which a runaway trolley threatens to kill
a man walking across the tracks and the only way to save the man is to save him is to throw him
out of the path of the train, thereby seriously injuring him.
The second way we extended the results of Experiment 1 was to investigate our subjects
knowledge of the consequentialist provision of the principle of double effect. As stated in 1,
the principle of double effect is a complex principle of justification requiring, among other
things, that the intended and foreseen good effects of an action outweigh its foreseen bad effects.
Our implicit assumption in Experiment 1 was that each of the scenarios used in that experiment
was mentally represented by our subjects as satisfying that condition. In particular, we took for
granted in Experiment 1 that individuals represented preventing the deaths of five people as an
intended and foreseen good effect that outweighed the foreseen bad effect of the death of one
person.
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In Experiment 2, we tested our subjects presumed knowledge of this consequentialist
provision of the principle of double effect directly by modifying one of the Foreseeable Battery
scenarios used in Experiment 1, so that an action described as throwing the switch, which
previously generated intended and foreseen good effects outweighed by its foreseen bad effects,
no longer did so, but rather generated the opposite result of its intended and foreseen good
effects being outweighed by its foreseen bad effects. We did this by taking one version of the
standard Bystander Problem and substituting a valuable thing - five million dollars of railroad
equipment lying idle across the tracks - for what was previously described as five men walking
across the tracks. We reasoned that our subjects would take for granted that the moral worth of
a person is greater than that of a valuable thing.
Finally, our third modification was to convert the experimental design of Experiment 1
from a between-subject design to a within-subject design. Although fully half of the participants
in Experiment 1 provided logically adequate justifications of their judgments, on inspection it
was clear that many of these justifications were unable to explain the alternating pattern of
intuitions generated in Experiment 1. For example, many of these nominally adequate responses
took the form of either simple deontological justifications (e.g., killing is wrong) or simple
utilitarian justifications (five versus one) that were manifestly incapable of explaining the
essential contrast between the Foreseeable Battery scenarios (i.e., the Trolley and Bystander
Problems), on the one hand, and the Intentional Battery scenarios (i.e., the Transplant and
Footbridge Problems), on the other. Hence in Experiment 2 we decided to examine this issue
and to begin to explore related issues such as framing effects by asking participants to provide
judgments and justifications of a pair of trolley problems presented to them simultaneously.
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3.1 Method
3.1.1 Participants
Participants were 65 adult volunteers between the ages of 22-35, 55 of whom were
graduate students at the John F. Kennedy School of Government at Harvard University, and 10
of whom were employees of the Cable News Network in Washington, DC. There were 33
women and 30 men. Two subjects did not provide information about their gender.
3.1.2 Stimuli and Procedure
Five scenarios were used, one of which was the Trolley Problem presented in 1.2. The
other four scenarios, which were our main concern in Experiment 2, are reprinted below. Each
was derived from a template that was designed to allow for systematic control and variation in
this and future investigations (Mikhail, 2000). Differences between the last three scenarios and
the first are underlined and italicized here to make them more noticeable. Participants were
given questionnaires without these markings.
The Bystander Problem (Hank: Foreseeable Battery)Hank is taking his daily walk near the train tracks when he notices that the train that isapproaching is out of control. Hank sees what has happened: the driver of the train sawfive men walking across the tracks and slammed on the brakes, but the brakes failed andthe driver fainted. The train is now rushing toward the five men. It is moving so fast thatthey will not be able to get off the track in time. Fortunately, Hank is standing next to aswitch, which he can throw, that will turn the train onto a side track, thereby preventing itfrom killing the men. Unfortunately, there is a man standing on the side track with his
back turned. Hank can throw the switch, killing him or he can refrain from doing this,letting the five die.
Is it morally permissible for Hank to throw the switch?
The Footbridge Problem (Ian: Intentional Battery)Ian is taking his daily walk near the train tracks when he notices that the train that isapproaching is out of control. Ian sees what has happened: the driver of the train saw fivemen walking across the tracks and slammed on the brakes, but the brakes failed and thedriver fainted. The train is now rushing toward the five men. It is moving so fast that
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they will not be able to get off the track in time. Fortunately, Ian is standing next to aheavy object, which he can throw onto the track in the path of the train, thereby
preventing it from killing the men. Unfortunately, the heavy objectis a man, standingnext to Ian with his back turned. Ian can throw the man, killing him or he can refrainfrom doing this, letting the five die.
Is it morally permissible for Ian to throw the man?
The Modified Bystander Problem (Karl: Bad Effects Outweigh Good Effects)Karl is taking his daily walk near the train tracks when he notices that the train that isapproaching is out of control. Karl sees what has happened: the driver of the train saw
five million dollars of new railroad equipment lying idle across the tracks and slammedon the brakes, but the brakes failed and the driver fainted. The train is now rushingtoward the equipment. It is moving so fast that itwill be destroyed. Fortunately, Karl isstanding next to a switch, which he can throw, that will turn the train onto a side track,thereby preventing it from destroying the equipment. Unfortunately, there is a man
standing on the side track with his back turned. Karl can throw the switch, killing him orhe can refrain from doing this, letting the equipment be destroyed.
Is it morally permissible for Karl to throw the switch?
The Modified Footbridge Problem (Luke: Consensual Contact)Luke is taking his daily walk near the train tracks when he notices that the train that isapproaching is out of control. Luke sees what has happened: the driver of the train saw aman walking across the tracks and slammed on the brakes, but the brakes failed and thedriver fainted. The train is now rushing toward the man. It is moving so fast that he willnot be able to get off the track in time. Fortunately, Luke is standing next to the man,whom he can throw off the track out of the path of the train, thereby preventing it fromkilling the man. Unfortunately, the man is frail andstanding with his back turned. Lukecan throw the man, injuring him or he can refrain from doing this, letting the man die.
Is it morally permissible for Luke to throw the man?
In the first scenario, the agent (Hank) must choose whether to throw a switch in order to
prevent a runaway train from killing five people, knowing that doing so will cause the train to
run down and kill an innocent bystander (henceforth Foreseeable Battery). In the second
scenario, the agent (Ian) must choose whether to throw a man in front of a runaway train in
order to prevent the train from killing five people (henceforth Intentional Battery). In the third
scenario, the agent (Karl) must decide whether to throw a switch in order to prevent a runaway
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train from destroying five million dollars of equipment, knowing that doing so will kill an
innocent bystander (henceforth Bad Effects Outweigh Good Effects). Finally, in the fourth
scenario, the agent (Luke) must decide whether to throw a man walking across the tracks out
of the path of the train, knowing that doing so will injure him (henceforth Consensual
Contact).
Unlike Experiment 1, which used a between-subject design, Experiment 2 employed a
within-subject design. Each of the 65 participants received a written questionnaire containing
two scenarios, including one or more of the four scenarios reprinted above. 6 Participants were
first asked whether the proposed actions were morally permissible and then to explain or
justify their responses. 25 participants were given the Intentional Battery scenario, 25
participants were given the Foreseeable Battery scenario, 25 participants were given the Bad
Effects Outweigh Good Effects scenario, and 25 participants were given the Consensual Contact
scenario. The assignment of participants to scenario type was random.
3.2 Results
3.2.1 Intentional Battery vs. Foreseeable Battery
We present the main results of Experiment 2 in stages, beginning with the comparison
between intentional and foreseeable battery (Figure 8). 2 of 25 subjects in the Intentional Battery
condition judged the action constituting intentional battery (throwing the man) to be
permissible. Meanwhile, 19 of 25 subjects in the Foreseeable Battery condition judged the
action constituting foreseeable battery (throwing the switch) to be permissible. This difference
is significant: x2 (1, N=50) = 24.4, p < .001.
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0
5
10
15
20
25
Intentional
Battery
Foreseeable
Battery
Permiss.
Impermiss.
Act Type
Subjects
Figure 8: Moral Judgments of Two Act Types in Experiment 2
(Intentional Battery vs. Foreseeable Battery)
X2 (1, N=50) = 24.4,
p < .001
0
2
4
6
8
10
12
Men Women Men Women
Permiss.
Impermiss.
Intentional
Battery
Subjects
Figure 9: Judgments of Two Act Types in Experiment 2 by Gender
(Intentional Battery vs. Foreseeable Battery)
Foreseeable
Battery
Act Type
X2 (1, N=21) = 11.4,
p < .001 (women).
X2 (1, N=27) = 13.38,
p < .001 (men).
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Male and female participants who were given these two scenarios showed a similar
pattern of responses (Figure 9). 2 of 14 men and 0 of 11 women in the Intentional Battery
condition judged throwing the man the action constituting intentional battery (throwing the
man) to be permissible. Meanwhile, 11 of 13 men and 6 of 10 women in the Foreseeable
Battery condition judged the action constituting foreseeable battery (throwing the switch) to be
permissible. These differences are also significant, x2
(1, N=21) = 11.4, p < .001 (women) and
x2 (1, N=27) = 13.38, p < .001 (men).
3.2.2 Good Effects Outweigh Bad Effects vs. Bad Effects Outweigh Good Effects
Next, we describe the results of Experiment 2 in terms of the weighing of good and bad
effects (Figure 10). As indicated, 19 of 25 subjects who were given the Hank scenario (now re-
categorized as Good Effects Outweigh Bad Effects) judged Hanks throwing the switch to be
permissible. By contrast, none of the 25 subjects who were given the Karl scenario (Bad
Effects Outweigh Good Effects) judged Karls throwing the switch to be permissible. This
difference is significant: x2 (1, N=50) = 30.65, p < .001.
Mens and womens responses followed the same pattern (Figure 11). 11 of 13 men and
6 of 10 women judged throwing the switch to be permissible in the Good Effects Outweigh Bad
Effects condition. By contrast, 0 of 14 men and 0 of 11 women held throwing the switch to be
impermissible in the Bad Effects Outweigh Good Effects condition. These results are also
significant, x2 (1, N=21) = 11.4, p < .001 (women) and x2 (1, N=27) = 19.99, p < .001 (men).
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0
5
10
15
20
25
Bad Effect >
Good Effect
Good Effect >
Bad Effect
Permiss.
Impermiss.
Act Type
Subjects
Figure 10: Moral Judgments of Two Act Types in Experiment 2
(Good Effects vs. Bad Effects)
X2 (1, N=50) = 30.65,
p < .001
0
2
4
6
8
10
12
Men Women Men Women
Permiss.
Impermiss.
Bad Effect >
Good Effect
Subjects
Figure 11: Judgments of Act Types in Experiment 2 by Gender
(Good Effects vs. Bad Effects)
Good Effect >
Bad Effect
Act Type
X2 (1, N=21) = 11.4,
p < .001 (women).
X2 (1, N=27) = 19.99,
p < .001 (men).
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3.2.3 Intentional Battery vs. Consensual Contact
Third, we examine the comparison between intentional battery and consensual contact
(Figure 12). As indicated, 2 of 25 subjects in the Intentional Battery condition (Ian) judged the
action constituting intentional battery (throwing the man) to be permissible. By contrast, 24 of
25 subjects in the Consensual Contact condition (Luke) judged the action constituting
consensual contact (throwing the man) to be permissible. This difference is significant: x2
(1,
N=50) = 38.78, p < .001.
Again, male and female responses conformed to the same pattern (Figure 13). 2 of 14
men and none of the 11 women in the Intentional Battery condition judged throwing the man to
be permissible. By contrast, all 7 of the men and all 16 of the women in the Consensual Contact
condition judged throwing the man to be permissible, x2
(1, N=27) = 27.0, p < .001 (women) and
x2 (1, N=21) = 14.0, p < .001 (men).7
3.2.4 Justifications
Finally, we turn to our subjects expressed justifications, that is, the responses they
provided to justify or explain their judgments. Because we utilized a within-subject design in
Experiment 2, we expected that these justifications would be significantly less adequate than the
corresponding justifications in Experiment 1, which relied on a between-subject design. In
addition, we predicted that subjects presented with both an Intentional Battery scenario and a
Foreseeable Battery scenario, in particular, would not be able to justify their conflicting
intuitions.
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0
5
10
15
20
25
Intentional
Battery
Consensual
Contact
Permiss.
Impermiss.
Act Type
Subjects
Figure 12: Moral Judgments of Two Act Types in Experiment 2
(Intentional Battery vs. Consensual Contact)
X2 (1, N=50) = 38.78,
p < .001
0
2
4
6
8
10
12
14
16
Men Women Men Women
Permiss.
Impermiss.
IntentionalBattery
Subjects
Figure 13: Judgments of Act Types in Experiment 2 by Gender
(Intentional Battery vs. Consensual Contact)
ConsensualContact
Act Type
X2 (1, N=27) = 27.0,p < .001 (women ).
X2 (1, N=21) = 14.0,
p < .001 (men).
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Both of these predictions were confirmed. First, 35.4% (23/65) of participants gave no
justification and 38.5% (25/65) provided logically inadequate justifications, while only 20.0%
(13/65) provided logically adequate justifications. This contrasts sharply with the Experiment 1,
in which 50% of subjects provided logically adequate justifications.
Second, only 10% (1/10) of those subjects who were given both the Intentional Battery and
Foreseeable Battery scenarios and who attempted to provide some sort of explanation for their
judgments provided logically adequate justifications. The other 90% (9/10) provided logically
inadequate justifications. Further, as Table 2 reveals, this groups expressed principles were
widely divergent. Many participants merely restated the problem they were asked to resolve or
otherwise provided answers which were non-responsive. Moreover, several participants
appeared puzzled by the nature and strength of their intuitions and by how those intuitions
shifted as a result of apparently minor and inconsequential differences in the relevant action
descriptions.
3.3 Discussion
The results of Experiment 2 corroborate and extend those of Experiment 1. First, they
lend further support to the hypothesis that both men and women possess intuitive or unconscious
knowledge of the prohibition of intentional battery and the principle of double effect. By
imputing knowledge of these principles to our subjects, we can explain and predict their moral
intuitions. Specifically, we can explain why their intuitions flip so predictably when the standard
Bystander Problem is modified so that the costs of throwing the switch outweigh its benefits and
the standard Footbridge Problem is modified so that throwing the man no longer constitutes
intentional battery.
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Table 2: Justifications for Bystander and Footbridge Pair of Problems in Experiment 2
Problem Type of
Battery
Judgment Justification
Bystander Foreseeable Permissible
Footbridge Intentional Impermissible
Very odd. I don't know why I chose differently in the secondscenario. The end result is the same. I just chose my gut
response--and now am intrigued with how to reconcile them.
Bystander Foreseeable Permissible
Footbridge Intentional Impermissible
It's amazing that I would not throw a person but throw a switch tokill a person. I really wish there was more I could do for the 1guy on the other track.
Bystander Foreseeable Permissible
Footbridge Intentional Impermissible
In either case, the moral decision rule depends on how close tothe active killing of the man is.
Bystander Foreseeable Permissible
Footbridge Intentional Impermissible
Not acceptable to decide to risk someone else's life to save others.
Bystander Foreseeable Permissible
Footbridge Intentional Impermissible
I know--five lives are five lives--it's all about the guts. That'swhat it comes down to. Blaise Pascal got it all wrong.
Bystander Foreseeable Permissible
Footbridge Intentional Impermissible
The man, Hank can here actively influence a sequence of eventswhich will limit damage (# of deaths). In the second event, hecannot throw another man onto the tracks because he will activelyand deliberately kill an innocent bystander. Really an impossiblechoice.
Bystander Foreseeable Permissible
Footbridge Intentional Impermissible
Moral actors may be forced to make a decision between two
passive choices where both will end rights. But to make actionover passive choices requires another kind of analysis and degreeof benefit.
Bystander Foreseeable Permissible
Footbridge Intentional Impermissible
In the first scenario it would be permissible to act as a utilitarianoptimizer. In the second rights come into question.
Bystander Foreseeable Permissible
Footbridge Intentional Permissible
I believe that the ultimate question is that of lives lost. Somewould argue that Hank and Ian would be morally justified in notstopping the train. While this may be true, it does not necessitatethat it be morally unjustified to stop the train.
Bystander Foreseeable Impermissible
Footbridge Intentional Impermissible
For the first scenario, I wanted to draw a distinction between "is itpermissible for him to throw the switch" and "does he have a dutyto throw the switch," though I don't know if that would havechanged my answer.
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Second, the results of Experiment 2 suggest that individuals have limited conscious
access to these principles (or to whichever principles are actually responsible for generating their
intuitions). Even under a liberal coding scheme, only 20% of subjects provided logically
adequate justifications for their judgments. Further, only 10% did so when asked to explain the
most challenging pair of moral intuitions, namely, the perceived contrast between the Bystander
and Footbridge problems.
Third, Experiment 2 provides some initial evidence of framing effects. Most notably,
only 76% (19/25) of respondents in the Foreseeable Battery condition judged Hanks throwing
the switch to be permissible, a much lower percentage than the 95% (19/20) of participants who
gave this response in Experiment 1. These effects were slightly less pronounced in males than in
females, but they were discernible in both groups: 85% (11/13) of men gave this response, as
compared with 100% (11/11) in Experiment 1, whereas 60% (6/10) of women gave this
response, as compared with 89% (8/9) in Experiment 1. These sample sizes are obviously quite
small, and it therefore would be premature to draw any firm conclusions about these effects at
this point. It seems likely, however, that a more systematic investigation of framing effects in
larger populations would yield significant results, perhaps including significant gender
differences. Nevertheless, the main pattern of intuitions Experiment 2 fell in line with those of
Experiment 1, in that both men and women in the aggregate recognized the relevant distinctions
among the Bystander, Footbridge, Good Effects Outweigh Bad Effects, and Consensual Contact
Problems. Hence Experiment 2 provides additional evidence that at least some moral intuitions
and the principles that generate them are widely shared, irrespective of demographic variables
like gender.
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4. Experiment 3
Participants in Experiments 1-2 included persons from countries other than the United
States, including Belgium, Canada, Columbia, Denmark, France, Germany, Israel, Japan, Korea,
Lebanon, Mexico, and Puerto Rico. Nonetheless, only one or a few individuals from each of
these countries were represented, and the majority of participants were United States citizens or
members of other Western nations. Accordingly, Experiment 3 was designed to investigate the
moral intuitions of a non-Western population.
4.1 Method
4.1.1 Participants
Participants were 39 adult volunteers ages 18-65 from the broader Cambridge,
Massachusetts community, all of whom had emigrated from China within the previous five years
and most of whom had done so within the previous two years. The group included 19 women
and 19 men 1 participant did not volunteer information about his or her gender. 8
4.1.2 Stimuli and Procedure
Same as Experiment 2, except that participants in this study were not asked to justify
their judgments. 14 participants were given the Intentional Battery scenario, 16 participants
were given the Intentional Battery scenario, 15 participants were given the Bad Effects Outweigh
Good Effects scenario, and 16 participants were given the Consensual Contact scenario. The
assignment of participants to scenario type was random.
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4.2 Results
4.2.1 Intentional Battery vs. Foreseeable Battery
Once again, we present the results of Experiment 3 in stages, beginning with the
comparison between intentional and foreseeable battery (Figure 14). 2 of 14 subjects in the
Intentional Battery condition judged the action constituting intentional battery (throwing the
man) to be permissible. Meanwhile, 11 of 14 subjects in the Foreseeable Battery condition
judged the action constituting foreseeable battery (throwing the switch) to be permissible.
This difference is significant: x2 (1, N=28) = 11.72, p < .001.
4.2.2 Good Effects Outweigh Bad Effects vs. Bad Effects Outweigh Good Effects
Due to the limited number of subjects in Experiment 3, we refrain from analyzing our
responses by gender. Instead, we turn directly to the comparison between good and bad effects
(Figure 15). 11 of 14 subjects in the Good Effects Outweigh Bad Effects condition judged
throwing the switch to be permissible. Meanwhile, only 1 of 15 subjects in the Bad Effects
Outweigh Good Effects condition judged throwing the switch to be permissible. This difference
is significant: x2 (1, N=29) = 16.81, p < .001.
4.2.3 Intentional Battery vs. Consensual Contact
Third, we examine the contrast between intentional battery and consensual contact
(Figure 16). 2 of 16 subjects in the Intentional Battery condition judged throwing the man to be
permissible. Meanwhile, 14 of 16 subjects in the Consensual Contact condition judged throwing
the man to be permissible. This difference is significant: x2 (1, N=32) = 18.0, p < .001.
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0
2
4
6
8
10
12
Intentional
Battery
Foreseeable
Battery
Permiss.
Impermiss.
Act Type
Subjects
Figure 14: Moral Judgments of Two Act Types in Experiment 3
(Intentional Battery vs. Foreseeable Battery)
X2 (1, N=28) = 11.72,
p < .001
0
2
4
6
8
10
12
14
Bad Effect >
Good Effect
Good Effect >
Bad Effect
Permiss.
Impermiss.
Act Type
Subjects
Figure 15: Moral Judgments of Two Act Types in Experiment 3
(Good Effects vs. Bad Effects)
X2 (1, N=29) = 16.81,
p < .001
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4.3 Discussion
The results of Experiment 3 suggest that the central findings of Experiments 1-2 are not
limited to persons educated or raised in the United States or other Western nations. Instead, they
suggest at least some operative principles of moral competence, including the prohibition of
intentional battery and the principle of double effect, are transnational and may be universal.
While claims of universality are often controversial and should be made with care, this
hypothesis is consistent with the role these principles already play in international law (i.e., the
law of nations). For example, the principle of double effects implied norm of non-combatant
immunitythat is, its prohibition against directly targeting civilians, together with its qualified
0
2
4
6
8
10
12
14
Intentional
Battery
Consensual
Contact
Permiss.
Impermiss.
Act Type
Subjects
Figure 16: Moral Judgments of Two Act Types in Experiment 3(Intentional Battery vs. Consensual Contact)
X2 (1, N=32) = 18.0,
p < .001
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acceptance of harming civilians as a necessary side effect of an otherwise justifiable military
operationhas long been part of customary international law and is codified in Article 48 of the
First Protocol (1977) to the 1949 Geneva Conventions (e.g., Henkin, Pugh, Schacter & Smit,
1993, p. 364-65). Likewise, the principle of double effects implied norm of proportionality is
also part of customary international law and is codified in Articles 22-23 of the Hague
Convention of 1907 (e.g., Henkin et al., 1993, p. 368). Further, many important legal doctrines,
in both American law and the domestic law of other nations, turn on an analysis of purpose and
the distinction between intended and foreseen effects (Mikhail, 2002). Hence it is perhaps not
surprising to discover that thought experiments like trolley problems, which implicate these
concepts, elicit widely shared moral intuitions from individuals of different cultural
backgrounds.
Nevertheless, while Experiment 3 provides some initial support for the existence of moral
universals, this support is obviously quite limited. More empirical investigation on a much wider
scale is necessary before specific claims about universality could be defensible. In the context of
our hypothesis, what would perhaps be most compelling in this regard would be to collect
additional evidence on trolley intuitions from individuals from around the world, in particular
those from markedly different cultural, social, religious, and socioeconomic backgrounds. To do
this, one would presumably need to translate these thought experiments into different languages.
One might also need to modify them in culturally specific ways, insofar as certain inessential
elements of the scenarios (e.g., trolleys) may be unfamiliar. We do not attempt these extensions
in this paper but merely identify them as objectives of future research which flow naturally from
the studies presented here.9
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5. Experiment 4
Experiments 1-3 suggest that the moral competence of adults includes the prohibition of
intentional battery and the principle of double effect. By attributing intuitive knowledge of these
principles to our subjects, we can explain and predict their moral intuitions.
As Table 3 indicates, the computations presupposed by this explanation can be
reconstructed in the simple form of series of yes-no questions or decision tree. Presented with a
presumptively wrong action, such as those harmful actions at issue in the Trolley, Transplant,
Bystander, and Footbridge problems, the decision-maker first asks whether the proposed actions
good effects outweigh its bad effects. If the answer is no, then the decision-maker concludes the
action is impermissible. If the answer is yes, then the decision-maker next asks whether the
action involves committing a battery as a means to achieve a given end. If the answer is no, then
the decision-maker concludes that the action is permissible. If the answer is yes, then the
decision-maker concludes that the action is impermissible.
Table 3: Explanation of Trolley, Transplant, Bystander, and Footbridge Intuitions as a
Function of the Principle of Double EffectProblem (Agent) Homicide? Battery? Good Effects
Outweigh
Bad Effects?
Battery as a
Means?
Deontic
Status
Trolley (Charlie) Yes Yes Yes No Permissible
Transplant (Dr.Brown) Yes Yes Yes Yes Impermissible
Bystander (Denise) Yes Yes Yes No Permissible
Footbridge (Nancy) Yes Yes Yes Yes Impermissible
Bystander (Hank) Yes Yes Yes No Permissible
Footbridge (Ian) Yes Yes Yes Yes Impermissible
Modified Bystander (Karl) Yes Yes No No Impermissible
Modified Footbridge (Luke) No No Yes No Permissible
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Table 3 illustrates that our central findings up to this point can be explained in the
foregoing terms. However, our findings are also consistent with an alternative explanation,
according to which trolley intuitions do not depend primarily on the mental state properties of an
agents action plan, but on its temporalproperties, in particular whether its bad effects (or its
prima facie wrongs such as battery) are mentally represented as occurring before orafterits
good effects. In particular, our central findings could be equally explained by the so-called
Pauline Principle, which holds that it is impermissible to do evil that good may come
(Anscombe, 1970 Donagan, 1977). Suitably formalized, a temporal interpretation of this
principle would in effect compute as impermissible any action plan which represents either a
bad effect or a battery occurring before a good effect. As Table 4 reveals, all but one of the
impermissible act representations examined thus far possess this property, the lone exception,
Karls throwing the switch in the Modified Bystander Problem, being explainable on other
grounds.10 Hence the Pauline Principle (or some suitable formalization of it) also constitutes
(part of) an observationally adequate explanation of the results of Experiments 1-3.
Table 4: Explanation of Trolley, Transplant, Bystander, and Footbridge Intuitions as a
Function of the Pauline PrincipleProblem (Agent) Homicide? Battery? Good Effects
Outweigh
Bad Effects?
Battery or Bad
Effects Prior to
Good Effects?
Deontic
Status
Trolley (Charlie) Yes Yes Yes No Permissible
Transplant (Dr.Brown) Yes Yes Yes Yes Impermissible
Bystander (Denise) Yes Yes Yes No Permissible
Footbridge (Nancy) Yes Yes Yes Yes Impermissible
Bystander (Hank) Yes Yes Yes No Permissible
Footbridge (Ian) Yes Yes Yes Yes ImpermissibleModified Bystander (Karl) Yes Yes No No Impermissible
Modified Footbridge (Luke) No No Yes No Permissible
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Experiment 4 was designed to investigate this logically possible alternative, as well as to
provide an additional check on the abstract concept of battery utilized in Experiments 1-3. To
accomplish these objectives, we constructed the following two new scenarios (Mikhail, 2000):
The Looped Track ProblemIntentional Battery (Ned)Ned is taking his daily walk near the train tracks when he notices that the train that isapproaching is out of control. Ned sees what has happened: the driver of the train sawfive men walking across the tracks and slammed on the brakes, but the brakes failed andthe driver fainted. The train is now rushing toward the five men. It is moving so fast thatthey will not be able to get off the track in time. Fortunately, Ned is standing next to aswitch, which he can throw, that will temporarily turn the train onto a side track. There isa heavy object on the side track. If the train hits the object, the object will slow the traindown, thereby giving the men time to escape. Unfortunately, the heavy object is a man,standing on the side track with his back turned. Ned can throw the switch, preventing the
train from killing the men, but killing the man. Or he can refrain from doing this, lettingthe five die.
Is it morally permissible for Ned to throw the switch?
The Looped Track ProblemForeseeable Battery (Oscar)Oscar is taking his daily walk near the train tracks when he notices that the train that isapproaching is out of control. Oscar sees what has happened: the driver of the train sawfive men walking across the tracks and slammed on the brakes, but the brakes failed andthe driver fainted. The train is now rushing toward the five men. It is moving so fast thatthey will not be able to get off the track in time. Fortunately, Oscar is standing next to aswitch, which he can throw, that will temporarily turn the train onto a side track. There isa heavy object on the side track. If the train hits the object, the object will slow the traindown, thereby giving the men time to escape. Unfortunately, there is a man standing onthe side trackin front of the heavy object, with his back turned. Oscar can throw theswitch, preventing the train from killing the men, but killing the man. Or he can refrainfrom doing this, letting the five die.
Is it morally permissible for Oscar to throw the switch?11
In the first scenario (Ned), battery is embedded within the agents action plan as a means. In
the second scenario (Oscar), battery is embedded within the agents action plan as a side
effect. Unlike the scenarios used in Experiments 1-3, however, the Ned-Oscar pair is not
distinguishable in terms of their morally neutral basic actions (e.g., throwing the switch vs.
throwing the man) or the temporal properties of their good effects, bad effects, and batteries.
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Instead, five fundamental properties are held constant between these two scenarios: (1) good
effects, (2) bad effects, (3) ultimate purpose or goal, (4) morally neutral basic action (throwing
the switch in each case), and (5) the temporal order of good effects, bad effects, and batteries.
Further, both are impersonal scenarios in the sense defined by Greene and colleagues (Greene
et al., 2001). The Ned-Oscar pair is therefore the pure