Neuroscience & the Soul

The nature of the human soul and that of the souls of other organisms has been studied extensively since Socrates, Plato, and then Aristotle went to work on the questions.  The brain, by contrast, has been accessible only very recently.  I expect that neuroscience is poised to tell us a lot about both the brain and the soul. 

One thing that neuroscience has determined, in my view, is that Cartesian dualism (or substance dualism) is untenable.  This is important because dualism remains the de facto view in the popular imagination.  Human beings (and maybe dogs, if indeed they all go to Heaven) have two complete bodies: a material one and an immaterial one.  At death and sometimes a bit earlier the latter cuts its ties with the former and drifts free.  The immaterial self is the genuine self; the material body is a mere vehicle.  The immaterial soul is the home of our thoughts, passions, and essential self. 

I like to note in passing that substance dualism may be what most Christians believe today but it is not the teaching of any major church.  The teaching of the churches is that of the resurrection of the body, suggesting that a human being without a human body is not really thinkable. 

Michael Gazzaniga’s famous split brain experiments pose a powerful challenge to substance dualism.  Gazzaniga examined patients who had had the corpus callosum cut as a therapy for extreme seizures.  This is the thick cable of nerves that connects the two hemispheres of the brain. 

Gazzaniga devised an experiment that had such a patient look at a dot on a screen.  Then a word was projected on the screen to the right of the dot.  This meant that only the right eye could see the word.  When he asked the patient to identify the word, the patient had no problem.  He would say “cat”.  That is because the right eye is wired to the left hemisphere of the brain and the latter is where the language centers are located. 

Now what happened when a word was projected to the left side of the dot?  The patient could not say what the word was.  See above.  However, and this is the fascinating part, the patient could draw a picture of the named object with his left hand.  That is apparently because the more artistic, image processing modules of the brain are located in the right hemisphere.  Whereas the left hemisphere could respond with language, the right hemisphere could respond only with a picture. 

If substance dualism were correct, and the seat of consciousness is an immaterial soul that is somehow connected to the physical body and brain, then this experiment shouldn’t have worked that way.  Information gathered by one half of the severed brain should have been uploaded to the uncut, immaterial soul.  It should then have been available to the other hemisphere, since the soul both receives information from the physical senses and commands the physical body.  That is precisely what did not happen. 

Instead, cutting the corpus callosum effectively cut one human being into two.  As long as the patient is looking at the world with both eyes, the two halves of the brain are working in tandem.  The two half-brains in one skull are not aware that anything has changed.  They can navigate the world well enough that no one else knows the difference, unless he is a neuroscientists conducting a clever experiment. 

Aristotle proposed (de Anima) that the soul was the actuality of life in a body with the potential for life.  Just as heat is the actual temperature of a physical medium that can be more or less hot, so the soul is the actual state of a living body that can be alive.  Aristotle was right.  Descartes wrong and so is Walt Disney.  Neuroscience can now tell us a lot about the soul because it is exploring the brain. 

Science Daily describes a study that linked a willingness to punish violations of moral rules with specific regions in the brain. 

The results of the study show that people only punish norm violations at their own expense if the dorsolateral prefrontal cortex – an important area for control located at the front of the brain – is activated. This control entity must also interact with another frontal region, the ventromedial prefrontal cortex, for punishment to occur.

The communication between these two frontal regions of the brain is also interesting in light of earlier fMRI studies, which showed that the ventromedial prefrontal cortex encodes the subjective value of consumer goods and normative behavior. As neuroscientist Thomas Baumgartner explains, it seems plausible that this brain region might also encode the subjective value of a sanction. This value increases through the communication with the dorsolateral prefrontal cortex. «Using brain stimulation, we were able to demonstrate that the communication between the two brain regions becomes more difficult if the activity in the dorsolateral prefrontal cortex is reduced. This in turn makes punishing norm violations at your own expense significantly more difficult.»

This study illuminates the neurological substratum of one of the key moral emotions, which in turn underlies moral behavior.  We are looking here at the activity of parts of the human soul. 

This is not, as one might worry, a reductionist account.  The activity of the various regions of the brain can only be understood in light of the moral activity that defines human action.  As a door knob depends on the existence of a doors, so the dorsolateral prefrontal cortex can be what it is only because it is part of a larger whole.  The parts are subordinate to the whole.  The material is what it is shaped into.  The soul is the actuality of the body. 

Evolution of Virtue 3

 Here is the third section of my paper on the evolution of virtue.  

Aristotle’s account of virtue is rooted in his understanding of biology.  He advanced a model of the human soul that was tripartite and hierarchical.  According to this model, human beings share with all organisms a basic level of soul that he called vegetative.  This level of soul includes such basic powers as feeding, growing, and producing waste.  It opens up an existential dimension of value that extends from flourishing to decay and death. 

While all animals share in the organic powers that make up vegetative soul, animals have powers that plants do not have: motility and perception at a distance.  These powers open up a second existential dimension: pain and pleasure.  Unlike plants, animals can have good and bad moments and good and bad days. 

Human beings obviously share in all of this.  Just as obviously, we alone possess a third basic power: logos.  Human beings are capable of speech and reason.  Logos makes it possible for us to distinguish between what something looks like and how it really is.  Most significant for moral thought, this means we can distinguish between what looks good and bad and what is really good and bad for us. 

Aristotle’s biology is unfortunately famous mostly for his howlers.  He believed in spontaneous generation, for example.  Yet he got most of it astonishingly right, according to modern evolutionary biology.  His tripartite soul maps very well onto evolutionary history.  Evolution does not work by adding new organisms to old ones built according to new blueprints.  Instead, it preserves what works while piling new systems on top of the older ones.  Some genes are unique to humans.  Others, like the famous tool box genes, are shared by all animals.  One the three basic systems that comprise the human brain is old enough to be called reptilian.  The neo-cortex, on the other hand, seems primary only in the primates. 

Aristotle models the human soul in much the same way as his teacher Plato (or Plato’s Socrates) did: by means of a political metaphor.  One part of the human soul is distinctly non-rational in so far as it does not respond to persuasion.  This includes all the organic activities that are rooted in the body and that are shared with other organisms.  It includes the sensations, among which are the pains and pleasures.  Logos, by contrast is uniquely human and its power is that of conscious thinking.  In between is what we might call the middle part of the soul.  This part of the soul includes the various passions.  Each passion includes an element of judgment: if I am angry, I am angry at someone about something.  Unlike the sensations (let alone the unconscious organic processes) the passions are rational in so far as they are susceptible to persuasion.  In the well-ordered human soul, reason rules the passions politically; i.e. reason both commands and persuades them.  Reason and passion together rule the sensations royally or even despotically, by command alone. 

From the viewpoint of evolutionary theory, the political metaphor is no mere convenience.  The passions develop their rational dimension precisely because they develop in the course of our evolution as political animals.  To the degree that human beings are capable of self-government, individually and collectively, it is because the psychological capacities underlying self-government were selected for.  The selection pressures that shaped these capacities were created by the advantages that highly cooperative human associations enjoyed.  Creatures capable of a sense of “we-ness” as Michael Tomasello has put it, who have a sense of moral obligation that they cannot easily escape, have largely inherited the earth.  Precisely because human souls were not fashioned anew but rather were built up out of preexisting psychological powers, it is both possible and necessary for the more rational elements to govern the less rational ones.  The moral dimension is one of the trajectories of our evolutionary history. 

When Aristotle looks for the nature of the virtues, he notes that there are three things in this human soul.  He is focusing here on consciousness or mind as modern philosophy calls it.  The three things are “feelings”, powers, and dispositions.  Under the first category, he explicitly lists a number of passions, including desire, anger, fear, and courage.  The powers indicate the capacity of the soul to generate the various feelings.  We can certainly suppose that there are creatures incapable of any of the feelings or only some and we can imagine that we might have existed with a different emotional palette.  By dispositions (or habits), he indicates that fact that each person may be disposed to experience each of the passions in an appropriate or inappropriate way.  Someone may be unable to feel sufficient anger when he has been genuinely offended or feel more anger than is reasonable in any situation. 

All three of these categories fit well within the context of an evolutionary analysis.  The emotions that we feel depend on an innate capacity to generate precisely this set of passionate motives.  Each emotive power exists in us because it was selected for.  In some set of circumstances that reoccurred frequently over time the power to produce an emotion contributed to the reproductive success of our ancestors.  To take a single example, a capacity for righteous indignation promoted cooperation by encouraging members of human communities to punish or ostracize those who violate fundamental social obligations.  When we see such violations, they look disgusting.  There is good evidence that the part of the brain that registers emotional disgust is the same part of the brain that registers physical disgust, as for example what we experience when we small rotting meat.  That is a good example of how evolution retools an existing emotive power for a fundamentally new function. 

To some degree, our emotional dispositions are innate.  Some persons are innately more prone to anger or compassion that others and men are in general more prone to violent aggression than are women.  On the other hand, in all or almost all human beings, the dispositions are flexible and subject to learning or conditioning.  Such flexibility makes every kind of sense in an evolutionary context.  It allows human communities to adapt to a wide range of environmental niches without having to suffer the losses that direct selection entails.  Whereas a species of bacteria might respond to a change in circumstances only after a catastrophic loss of numbers, a human society might respond simply by changing the characteristic behavior of its members.  It also allows the community to cultivate certain passions in certain ways, thus producing what we would call moral culture.  Finally, it allows an individual to cultivate himself. 

The Evolution of Emotions

Stephen T. Asma has a very interesting piece on the evolution of emotion in Aeon.  Asma is Professor of Philosophy at Columbia College, Chicago.  The essay is part travel story and part summary of “the new field of affective neuroscience.” 

Asma pushes a number of provocative ideas that seem very plausible to me.  One goes like this:

It might seem self-evident to the sentimental pet owner that our fellow creatures have emotions, but science has long been loath to admit it. Yet Jaak Panksepp, professor of veterinary anatomy at Washington State University College, says this is one area where our anthropomorphic tendencies are probably in the right: animals do have complex emotional lives.

This involves the familiar problem of anthropomorphizing animals.  Just because a snarling dog looks angry to me doesn’t tell me whether he experiences anger in anything like the way I do.  On the other hand, assuming that animals are not capable of emotional states seems to me to reek of dualism; that is, it supposes that human beings possess a soul that is so unique as to remove us from the category of animals.  I suggest that the latter leads us further astray than anthropomorphizing animals ever did. 

Ethologists who study animal behaviour increasingly accept the idea that fear keeps animals away from predators, lust draws them toward each other, panic motivates their social solidarity and care glues their parent-offspring bonds. Just like us, they have an inner life because it helps them navigate their outer life.

That is the most parsimonious interpretation of the phenomena.  A second idea is that human minds emerge from a series of “brains” arranged one atop the other. 

Neuroscience has begun to correct the computational model by showing how our rational, linguistic mind depends on the ancient limbic brain, where emotions hold sway and social skills dominate. In fact, the cognitive mind works only when emotions preferentially tilt our deliberations…  Our rational mind is truly embodied, and without this emotional embodiment we have no preferences. In order for our minds to go beyond syntax to semantics, we need feelings. And our ancestral minds were rich in feelings before they were adept in computations [my italics].

Our neo-cortex mushroomed to its current size less than one million years ago. That’s a very recent development when we remember that the human clade or group broke off from the great apes in Africa 7 million years ago. That future-looking, tool-wielding, symbol-juggling cortex grew on top of the limbic system. Older still is the reptile brain — the storehouse of innate motivational instincts such as pain-avoidance, exploration, hunger, lust, aggression and so on. Walking around (very carefully) on the Serengeti is like visiting the nursery of our own mind.

I have pointed out here that this hierarchically layered model of the mind was explicitly advanced by Aristotle in his masterful On the Soul.  I suggest that Aristotle’s view corrects for both dualism and anthropomorphizing.  It presents an embodied mind that allows the human being full ontological status without divorcing it from its animal origins. 

Asma has some criticisms of evolutionary psychology. 

Evolutionary psychologists have tried to apply Chomsky’s module idea to almost every other mental activity. What kind of food we like, what kind of spouse we’re looking for, our phobias of snakes and spiders, our preference for certain kinds of stories, even our ability to detect cheaters in a group: all have been attributed to specialised programs in the brain. This neat, formulaic explanation of human psychology plays well in the popular press, but it seems less convincing as we learn more about brain development and early human ecology.

Its chief rival is the school of ‘general intelligence’. According to this view, the neocortex is a highly flexible, general problem solver. Our environment selected for a mind with reliable pattern recognition and prediction powers, but it didn’t give us specific modules for thought contents or behaviors. As affective neuroscience advances, this scenario comes to look more credible, albeit with a surprising twist. It seems that even the emotional springs of the limbic system — our fear, care, rage and so forth — are more pliable and open-ended than we previously thought…

This criticism seems to be confused.  Evolutionary psychology does seek to identify evolved psychological mechanisms, but it hardly insists that these mechanisms are inflexible.  Mental schema for distinguishing kin from non-kin, allies from enemies, have to be flexible and responsive to context.  Moreover, flexibility seems to come chiefly from having a considerable number of distinct mechanisms that may be drawn upon in a pinch, each one of which enables novel responses in novel contexts.  The whole point of the layered theory of mind advocated by Asma is that human intelligence depends on a lot of prepackaged software, something that is very different from any notion of “general intelligence.” 

Another death-knell for old-school evolutionary psych might be sounding from the field of hominin-era climate studies. A vital premise for the modular theory is that our minds evolved in an extremely stable, unchanging environment. If our current minds are a mishmash of Pleistocene adaptations, then the conditions that shaped our brains must have been very consistent, or else natural selection couldn’t sculpt each module to fit our perennial environmental challenges. But it now appears (thanks to the work of paleoanthropologists such as Rick Potts) that the environment was anything but stable during the brain boom. In fact, it was precisely the climate chaos of this era that created our multipurpose, problem-solving minds.

Again, there seems to be some confusion.  Human beings share some of our genetic heritage with all other animals.  Tool box genes are one example.  The layered theory of mind that Asma advocates tells us that we share significant parts of our brain’s architecture with other animals, including reptiles.  That means that some parts of our environment have not changed significantly over the course of evolutionary history.  Just as the astonishing stability of ants over millions of years points to an environmental niche that was very stable, so the presence of reptilian architecture in the human brain suggests that some environmental challenges have been persistent for very long periods of time. 

No doubt the environment of evolutionary adaptation was subject to a lot of changes, due to climate and other factors.  Regardless of those changes, our ancestors still had to find mates and allies.  Females had to make sure their investments were as secure as possible and males still had to make sure they were investing in the right offspring.  If evolutionary explanations are worth anything, it is because some things change while others do not. 

I look forward to more from affective neuroscience.  It certainly looks like the right idea.