Review of Antonio Damasio's "Descartes Error"

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Review of Antonio Damasio's  Descartes' Error: Emotion, Reason, and the Human Brain. Avon Books, New York, 1994.



Antonio Damasio, a respected behavioral neurologist at the University of Iowa, has made important contributions to the understanding of vision, memory and language. With this work, he aims for a broader target, namely an exploration of "the neurobiology of human rationality."

The book provides the practicing neuroscientist ample food for thought, but it is also accessible to the educated layperson. The neurobiology is only moderately detailed, and the writing style is lucid and elegant. In overview, one finds eleven chapters in three sections. In section one, Damasio recounts seminal neurologic discoveries showing that certain brain functions are compartmentalized in specialized areas. He leads the reader through the famous story of Phineas P. Gage, a nineteenth century railway worker who miraculously survived an explosion that drove a three-foot-long iron rod through his brain. Remarkably, Gage survived without paralysis and without intellectual decline. Within two months he was pronounced cured, but he was never again himself. His personality and his ability to function in society were severely compromised. Gage provided the first clues that there are "systems in the human brain dedicated to the personal and social dimensions of reasoning."

Damasio provides additional examples that emotion and rationality can be damaged by focal brain injuries. He then reviews the neuroanatomy and neurochemistry of the prefontal and limbic regions that are known to be critical for reason and emotion. In section two, he synthesizes his speculations about how human reasoning works and how this working came to be. In section three, he gives experimental evidence supporting his speculations, and he explores the philosophical and moral implications raised by them.

One might have subtitled this "A Critical Critique of Pure Reason," suggesting its departure from Kant as well from Descartes. Like many reared in the scientific tradition, Damasio recalls that he grew up "accustomed to thinking that the mechanisms for reason existed in a separate province of the mind, where emotion should not be allowed to intrude." Yet his experience with patients like Gage convinced him that normal human reasoning is inextricably linked to emotion: "Reason may not be as pure as most of us think it is or wish it were...Emotions and feelings may not be intruders in the bastion of reason at all: they may be enmeshed in its networks for worse and for better."

Pure reason, reason uninfluenced by emotion, seems to occur only in pathological states that are characterized by impairment of day-to-day decision-making and social interaction. Says Damasio, "Certain aspects of the process of emotion and feeling are indispensable for rationality." To think otherwise was Descartes' error. "(The error was) the abyssal separation between body and mind, between the sizable, dimensioned, mechanically operated, infinitely divisible body stuff, on the one hand, and the unsizable, undimensioned, un-pushpullable, nondivisible mind stuff; the suggestion that reasoning, and moral judgement, and the suffering that comes from physical pain or emotional upheaval might exist separately from the body. Specifically: the separation of the most refined operations of the mind from the structure and operation of a biological organism."

Damasio is clear about why Reason depends upon Emotion. It flows directly from evolution's first commandment (Survive!), and from the fact that "evolution is thrifty and tinkering."

"(Evolution) has had available, in the brains of numerous species, decision-making mechanisms that are body-based and survival-oriented, and those mechanisms have proven successful in a variety of ecological niches... Natural selection tends to work precisely this way, by conserving something that works, by selecting other devices which can cope with greater complexity, rarely by evolving entirely new mechanisms from scratch." Early nervous systems evolved innate patterns of activity to reliably control basic reflexes and drives promoting survival (respiration, feeding, fight-flight behavior) and species perpetuation (sexual behavior, care of kin). Emotions and feelings (also patterns of neural activity) evolved as manifestations and facilitators of these basic functions.

Supra-instinctual capacities such as rationality emerged as nervous systems became increasingly complex in response to "the daunting task of predicting an uncertain future and planning out actions accordingly." Yet, rationality is dependent upon the operation of two crucial neural processes: attention and working (short term) memory. As it turns out, emotions can activate both of these processes. Nature, Damasio says, "has built the apparatus of rationality not just on top of the apparatus of biological regulation, but also from it and with it."

Exactly what happens in the process of reasoning is unknown, Damasio admits; but he is not without ideas. It is difficult to do justice to his ideas in the space of this review, but I will sketch them out.

Pain and pleasure are patterns of neuronal activity that serve as "the levers that the organism requires for instinctual and acquired strategies to operate efficiently." Neural-pattern "images" are created from ensembles of neurons firing in relative synchrony and harmony. These "images" form the basis of "somatic markers" (representing body states) and "dispositional representations" (which include acquired knowledge).

The frequency of occurrence of these neuronal firing patterns determines in part the strength of the synaptic connections among nerves in the ensemble. The strength of the connections in turn creates a bias as to how easily a given ensemble can be reactivated at a later time. Biases help to select responses from a virtually infinite set of potential options.

Damasio postulates that zones in the prefrontal regions initially developed to guide responses to socialization with other members of the species, but logic and rationality were built from this same prefrontal scaffolding. "The machinery that helps you decide whom to befriend would also help you design a house in which the basement will not flood."

There no "place" in the brain where all of this is "viewed." Rather, there are "convergence zones" where signals from disparate brain regions (representing internal states and encounters with the environment) are correlated and transiently bound together. It is largely in the prefrontal region that the mindscape is created. Processes there bring together a "continuous creation of combinations of entities and events, resulting in a richly diverse juxtaposition of images." Changeux has suggested this region be labeled the "generator of diversity," or GOD for short.

The primordial representations of the body in action offer a spatial and temporal framework upon which other representations are grounded. Damasio speculates that these primordial representations might provide "a core for the neural representation of self and thus provide a natural reference for what happens to the organism, inside or outside its boundary." The self envisioned by Damasio is not the self of Descartes, however. Rather, self emerges from the continuous re-creation of the overall patterns of somatic markers and dispositional representations.

To a considerable extent, basic patterns of neuronal activity are genetically "hard-wired," but our one-hundred thousand genes are inadequate to give specific instruction to the wiring of our ten trillion synapses. That we can learn and remember our experiences tells us that interaction with the environmental helps to shape the fine structure of our brains. This plays out amidst a continually changing background of feedback-feedforward neural activity. The body's hormonal environment strongly influences the brain and vice versa. The external environment, interpersonal interactions, culture and education are but some of the other influences that must be considered. Understanding all of this in a satisfactory manner is an endeavor that Damasio calls "truly daunting."

But, I digress. Damasio's central points are these: 1) Emotion is fundamental to reason. 2) "The human mind and the rest of the body constitute an indissociable organism, integrated by mutually interactive biochemical and neural regulatory circuits." 3) "The organism interacts with the environment as an ensemble: the interaction is neither of the body alone nor of the brain alone." 4) "The physiological operations that we call mind are derived from the structural and functional ensemble rather than from the brain alone. Mental phenomena can be fully understood only in the context of an organism's interacting in an environment."

In closing, consider some implications of Damasio's thesis. Science is founded upon experiment and ratiocination. Scientists value insight and a sense for beauty, but they distrust and eschew emotion in their professional work. If Damasio is correct, however, emotionless reasoning may be pathological and counterproductive. If emotion is inherently part of human reasoning, what becomes of scientific objectivity? Blaise Pascal once said, "The heart has its reasons of which reason knows nothing." If Damasio is correct, so is Pascal. Is science willing, or able to allow for that?

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