Book Review
Damasio's Proposition: A review of Damasio, A. (1994). Descartes' Error: Emotion,
Reason and the Human Brain. New York: G.P. Putnam's Sons (312 pages).
Reviewed by CORINNE ZIMMERMAN, University of Alberta
Descartes'Error is the provocative title of Damasio's (1994)
book in which he proposes that emotion and reason are
inextricably linked, an idea that runs counter to common
folk wisdom but with potentially profound implications
for neuroscience, cognitive science, and philosophy. Not
since James Watson's (1968) The Double Helix, has a book
about a scientific endeavor been as captivating. Damasio
describes the book as "a conversation," but it is also an
engaging presentation of empirical neuroscience research,
history, and philosophical questions. As Descartes' Error
may also be of interest to academic psychologists and
neuroscientists, this review will provide (a) a general
description of Damasio's book, (b) an outline of the
development of the somatic-marker theory that he
proposes to account for the evidence suggesting a relation
between emotion and reason, and (c) a brief evaluation of
this hypothesis.
General Overview ofDescartes' Error
Gage and Elliot: A starting point. Damasio has divided the
book into three sections. In the first section, he tells the
tale of Phineas Gage, the colorful character who sustained
both brain damage and severe personality change following an explosion that blew a 3-foot tamping iron through
his skull. Damasio uses Gage's story as a starting point for
an exploration of the connection between prefrontal brain
damage and impaired rationality. Damasio then examines
the behavioral consequences in other cases of prefrontal
damage. What emerges is an apparent pattern of behavior
involving flattened affect accompanied by impaired
reasoning in real-world domains. Damasio refers to this
pattern as "Gage Matrix." These cases of prefrontal
damage hinted at the possibility that certain brain regions
may be responsible for the ability to plan future survival
within a complex social environment, and that this ability
relies upon intact systems underlying both cognition and
emotion.
The next breakthrough in Damasio's thinking about
the coupling of localized brain damage with decision
making deficits was the case of Elliot, a patient with a
ventromedial prefrontal tumour in the same region of the
brain that was damaged in Gage. Yet an extensive battery
of laboratory tests failed to show that Elliot was impaired
in any way. He clearly had intact cognitive abilities,
knowledge of and access to social rules, and the ability to
generate options and scenarios. In spite of this, he was an
emotionally contained and ineffective social being unable
to manage his affairs and to select the most advantageous
course of action with respect to his personal life. Elliot's
case led Damasio to consider that a lack of emotion could
be responsible for poor decision making and irrational
behavior.
Damasio also considers evidence from cases of brain
damage in regions beyond the prefrontal cortices that
nevertheless also result in behavior consistent with "Gage
Matrix." He proposes a neural circuit that might be
responsible for the connection between emotion and
reason, and suggests that damage to this circuit may result
in "Gage Matrix." The collection of systems underlying
this neurological condition includes the ventromedial
prefrontal cortices, the right somatosensory cortices, and
subcortical regions (e.g., the amygdala). This collection of
systems is involved in goal-oriented reasoning and
decision-making, emotion and feeling, and the processing
of bodily signals.
The Journey Towards an Explanation. In the second
section, Damasio starts to assemble an explanation to
account for the phenomena presented in the first section,
that is, the "mysterious alliance" of emotion and reason.
Damasio defines key terms and lays out the assumptions
required to take part in the "conversation." Fundamental
concepts such as brain, body, mind, behavior, the nature
of decision making, feeling, and emotion are delineated.
He also discusses the neural basis of knowledge and its
dependence on images. Other topics include biological
regulation and survival, the differences between emotion
and feeling, and the mechanisms responsible for connecting emotion and decision making. This exploration is
necessary to prepare the reader for Damasio's presentation
of the somatic-marker hypothesis, to be described shortly.
The Somatic-Marker Hypothesis and the Mind-Body
Problem. In the third section of the book, Damasio
presents some of the initial attempts to test experimentally
the somatic-marker hypothesis. In the last two chapters,
he turns his attention to the assertion that "the body, as
represented in the brain, may constitute the indispensable
frame of reference for the neural processes that we experience as the mind" (p. xvi). This part of the conversation is
Canadian Journal of Experimental Psychology, 1996, 50:3, 330-332
Book Review
the most philosophical, although it is grounded in and
relies upon the previous discussions of the neurobiology
of rationality and emotion.
Damasio 's Proposition: The Somatic-Marker Hypothesis
We spend a considerable amount of time planning for the
future. We do our planning within a social context,
following rules of social conduct while selecting courses of
action most advantageous to personal survival and wellbeing. Psychologists have done much research on the
strategies people use when deciding how to solve, for
example, a mathematical problem or a logical puzzle (e.g.,
VanLehn, 1989). However, the strategies one might use
when deciding on the best career, marriage partner, or
investment portfolio seem, at least on an intuitive level, to
be different from the ones we use to solve such logical
puzzles. There are many more response options and the
consequences of such decisions have implications for
future well-being. When reasoning within a social domain,
the accuracy with which we can predict certain outcomes
is diminished. But most people still manage to navigate
through their personal and social lives despite the complexity and uncertainty. So the question that inevitably
arises is, "What in the brain allows humans to behave
rationally?" (Damasio, 1994, p. 85).
Damasio suggests that there are two alternatives to
explain rational (and irrational) behavior: the "high
reason" view, and the somatic-marker hypothesis.
The former would suggest that when faced with a situation requiring a choice, one performs some type of
cost/benefit analysis on the various options, calculating
the best outcome by keeping emotions in check. This
simple description captures the essence of both traditional
wisdom and philosophical prescriptions. However,
according to Damasio, this strategy is not the most fruitful
one, nor does it describe how we make rational choices.
First, generating a list of potential options and performing
cost/benefit calculations on each option relative to the
others would tax the capacity of attention and working
memory. Second, even with paper and pencil, most
decisions must be made within a finite time period.
The somatic-marker hypothesis is Damasio's alternative. Here, when one is faced with a situation requiring a
choice, when certain response options come to mind, a
fleeting and unpleasant "gut feeling" may accompany the
thoughts of some of those options. This is the essence of
the somatic-marker hypothesis: a bodily feeling (or
"somatic" state) "marks" the image of a possible response
option. Somatic-markers can be seen to work by drawing
attention to possible positive or negative outcomes of a
particular alternative. In this way, a large number of
alternatives may be dismissed almost immediately, thereby
protecting the individual from potentially harmful future
consequences. Left with a smaller pool of reasonable
options, one may then use some type of cost/benefit
reasoning.
Damasio believes that patients with
"Gage Matrix" have brain damage that compromises their
ability to feel the emotional or bodily sensations that arise
when they consider the various alternatives to a course of
331
action. Because somatic-markers function as a biasing
device, or a type of alarm system that aids in deliberating
about future decisions, the absence of these somaticmarkers reduces the efficiency of the decision-making
process. The result of this partnership between bodily
sensations and decision making is an inseparable connection between body and mind. Because Descartes envisioned thinking to be separate from the body, we now see
the "error" that Damasio has alluded to.
An Evaluation of the Somatic-Marker Hypothesis
Descartes' Error represents Damasio's attempt to outline
the key features of the somatic-marker hypothesis,
including its history, rationale, assumptions, and predictions. Is it worthy of our attention yet? Should we
seriously consider the possibility that feeling and emotion
are an integral component of rational decision making?
The hypothesis is intriguing on several counts.
First, the reader definitely develops the sense that the
somatic-marker hypothesis is a well-developed idea.
Damasio traces the formation of the hypothesis from the
rudimentary questions posed by the mysterious behavioral
consequences following prefrontal damage, through a
consideration of the neurobiology of emotion and feeling,
to the proposal for a mechanism that might be responsible
for the counterintuitive connection between reason and
emotion. Damasio developed the hypothesis following a
consideration of data from several sources, including
historical data, case studies, and both human and animal
data.
Second, the theory that Damasio proposes is very
thorough in many respects. It takes into account that
these systems are part of a functioning person living
within a culture with general survival as a goal. Damasio
does not ignore the fact that we are biological systems
with "lower level" regulatory mechanisms, drives, and
instincts at the expense of focusing solely on our capacity
for "high reason." The theory takes into account development with respect to both the individual person and
evolutionary theory. He tentatively proposes that the
systems that developed probably did so because it was
both adaptive and because of evolutionary conservation.
With respect to individual development, he provides the
necessary account of how somatic-markers are formed,
which is consistent with current knowledge about learning, socialization, and biological regulation.
A third feature that makes the somatic-marker hypothesis worthy of attention is the fact that it is a relatively
parsimonious theory that may account for a range of
psychological phenomena. It may account for how it is
that we make rational decisions about issues as complex as
choosing a career or voting, and as instinctive as moving
to avoid a falling object or eating dinner. We can also
appeal to it to explain what we know of as "intuition." It
may also account for why it is that we do not always
choose courses of action that offer immediate or shortterm reward. We can envision long-term positive outcomes, and the pleasant somatic states that mark those
images, and use these to postpone more immediate
332
gratification (e.g., finishing medical school rather than
quitting). Furthermore, the hypothesis may be used to
explain decision making in both normal and brain damaged populations.
Fourth, the somatic-marker hypothesis that Damasio
outlines is clearly testable. It has heuristic value in that it
is sufficiently well-developed to derive unique predictions
and stimulate novel research. Damasio includes his initial
attempts to test these predictions empirically in research
using a skin conductance response paradigm. Unlike
traditional cognitive theories, there are clear connections
to the underlying brain systems and mechanisms. Even if
the exact systems that Damasio proposes are not implicated, future research could be used to refine the model as
empirical findings confirm or disconfirm its predictions.
Zimmerman
intriguing, a good starting point would be to engage in
Damasio's "conversation." His presentation of the
somatic-marker hypothesis will pique interest and may
serve to guide new research to test the tenability of this
theory. He has highlighted the importance of that illdefined aspect of human existence known as "emotion,"
and brought it to the forefront, a step that may make it
not only respectable to consider in future research, but
necessary.
Address correspondence to Corinne Zimmerman, Department
of Psychology, P-220 Biological Sciences Building, University of
Alberta, Edmonton, Alberta T6G 2E9 (e-mail: czimm@
psych.ualberta.ca)
References
Concluding Remarks
Descartes' Error is an entertaining, educational and
thought-provoking journey. Damasio does a remarkable
job of bringing together a diversity of topics that are often
studied and discussed separately - cognition, emotion,
learning, neuroanatomy, personality, evolution, and
philosophy of mind. Should psychologists and
neuroscientists take up the implicit challenge to consider
the interface between cognition and emotion and the
underlying neural mechanisms? If the challenge sounds
Damasio, A.R. (1994). Descartes' error: Emotion, reason, and the
human brain. New York: G.P. Putnam's Sons.
VanLehn, K. (1989). Problem solving and cognitive skill acquisition. In M. Posner (Ed.), Foundations of cognitive science (pp.
527-579). Cambridge, MA: MIT Press.
Watson, J.D. (1968). The double helix: A personal account of the
discovery of the structure ofDNA. New York: New American
Library.
Date of acceptance: July 7, 1996