Rationality and its Limits

Rationality depends on emotion.  A.R. Damasio’s Descartes’ Error – Emotion, Reason and the Human Brain reveals how the human ability to make rational, prudent choices fails unless it is supported by normal emotional responses.  His findings fly in the face of conventional wisdom which portrays emotions as enemies to reason – impulsive forces which urge us to make poor choices, and which must be held in check by cool logic and deduction.

Damasio shows that rational behaviour results from a bottom-up process that begins with subconsciously learned emotional responses that can be detected in galvanic skin responses (GSR’s), and other physical signs.  This unconscious learning preceeds, and helps to facilitate, cognitive learning.

Moreover, people require these learned emotional responses to make rational, self-interested choices, even after they have cognitively ‘figured out’ what choices are in their interests.

Both results seem counterintuitive, the latter most strikingly.  Most people who consider themselves sane think that if they know what is in their best interests, they will choose accordingly.  They won’t, says Damasio, unless that knowledge is supported by feeling. He offers two explanations for this.

The first is that conscious reasoning is a relative latecomer to the evolutionary stage.  Perception and adaptive behavioural response began in animals much more primitive than ourselves.  Rational decision-making is not a new capability which superceded the old, instinctual and unconscious behavioural controls; rather, it is an organic extension of those more primitive processes.  Yes, we are capable of conscious deliberation; we can weigh alternatives, think things through, consider future scenarios.  But in doing so we continually rely on how we feel about things.  We are guided by emotional “markers” which attach both to our present perceptions of situations in which we find ourselves (“I just don’t trust this guy”) and to imagined futures (“I wouldn’t feel comfortable investing in something like that”).  Evolution works by adapting and refining old capabilities to meet new situations.  Our reasoning processes are not ‘pure’, but are grounded in all the same basic mechanisms as the ‘irrational’ processes that govern the behaviour of animals.

If basic biological regulation is essential to the guidance of personal and social behaviour, then a brain design likely to have prevailed in natural selection may have been one in which the subsystems responsible for reasoning and decision making would have remained intimately interlocked with those concerned with biological regulation, given their shared involvement in the business of survival. (Damasio 1994, p 85)

Damasio’s account explains the well-known parasympathetic symptoms of emotions: the galvanic skin responses, muscular tension, excretory impulses, elevated heart rate, flushing associated with strong emotion.  These vivid ‘somatic markers’ are typically more strongly connected with the emotions of self-concern than with more altruistic feelings.  Damasio’s account of emotions echoes that of William James, in The Principles of Psychology:

If we fancy some strong emotion and then try to abstract from our consciousness of it all the feelings of its bodily symptoms, we find we have nothing left behind….  What kind of an emotion of fear would be left if the feeling neither of quickened heartbeat nor of shallow breathing, neither of trembling lips nor of weakened limbs, neither of gooseflesh nor of visceral stirrings, were present, it is impossible for me to think.

Emotional feelings, says Damasio, are “first and foremost about the body”, giving us “the cognition of our visceral and musculoskeletal state”. (Damasio 1994, p159)

The second reason emotions are indispensible is that the job of choosing from among the myriad available behavioural options is more than can be handled by conscious deliberation.  Consciousness is slow and computationally expensive.  Making all the decisions we make is simply too big a task.  To get the job done, we rely heavily on emotional markers associated with imagined alternatives.  Usually, these emotional markers are attached automatically, by subconscious processes.  We experience them as a kind of enhanced perception: a patina of affect, colouring almost everything we perceive or imagine.  They function as a kind of shorthand, efficiently and effectively guiding our action.

Damasio’s theory is that emotional markers reduce computational load, and allow us to perform well – rationally, consistently with our considered values – in complex situations, especially social situations, about which we have incomplete information, and in which responses are time-critical.  Our emotional responses to situations and events do the grunt work of decision-making.  If we had to rely on consciously recognizing patterns of experience, forming hypotheses, marshalling evidence, performing statistical analyses, in order to decide how to behave, we’d be left at the starting gate.

When making decisions like choosing a career, deciding whom to marry, what to invest in, or how to design a building, “complexity and uncertainty loom so large that reliable predictions are not easy to come by.”  Damasio argues that such matters are too complex to be effectively decided by deduction alone, especially when, as is often the case, decisions must be made quickly.  One needs heuristic aids; and that is what emotional markers are.  They are like a trusted consiglieri at our elbow, who, with a word or a nudge, draws our attention to subtle dangers and veiled opportunities.

An Example of Decision-making

Almost always, when I set out on a walk, I consciously decide on the destination.  I may also consciously choose a route, but only in outline.  As I walk, I constantly monitor the details of my path, building a three-dimensional mental model of the trail or sidewalk immediately ahead.  Normally, such monitoring requires little conscious attention: I can think about other things, such as work, or, if I have a companion, I can engage in conversation.  I can move quickly along a forest trail, at a steady 5 km/h (3 mph) if the way is not too rough or steep.  As I walk, my eyes saccade along fifty feet or so of the path ahead, again and again.  Automatically, my brain plans the places where my feet will fall, so as to cause as little interruption to my stride as possible; and my feet follow this path.  I do not usually have to look at my feet.   If the path is very rough, or the footing unstable with loose rocks, I slow down, and I do watch my feet.

Certain events can command my full attention: a problem on my walk, such as encountering a rope barrier and a sign that says, Trail closed because of landslide.  I stop and think about what to do.  I could obey the sign, and take a longer, less enjoyable route.  Or, assuming that the parkskeepers are erring on the side of caution, so as to avoid the remotest chance of a lawsuit, I might step over the rope and continue, trusting in my own ability to safely circumnavigate a wash-out on the path.

What goes on during that decision process?  I think about taking the alternative route, and feel that the experience would be disappointing.  I consider how dangerous the washed-out trail is likely to be.  I imagine a scenario where I fall into the Capilano River.  That would be a bad outcome – the river being swift, turbulent, and cold in winter – but its probability is so low that I disregard it.  Having seen slides on trails in the area before, I conjure up a mental picture of a minor hazard that I can easily spot and circumvent.  It is full daylight; twilight would elevate my sense of danger.  Finally, I think about encountering parks personnel – an unlikely possibility, but much likelier than falling in the river.  To be challenged would be slightly embarrassing, but no real harm done.  Having weighed these alternatives, I decide to step over the barricade and continue.  Much more of my conscious attention is occupied with the trail than before, until I come to the hazard and bypass it safely.  Then my mind gradually reverts to its former mode, in which only a fraction of my conscious resources are used to navigate the trail.

Damasio’s hypothesis that emotional associations guide my decision-making process seems borne out in my experience.  The possible outcomes I imagine – falling in the river, taking the less scenic alternate route (which, besides being boring, might make me late), successfully bypassing the hazard, being challenged by parks personnel – all have some emotional colouring.  They are tinged with positive or negative affect.  That emotional colouring is boosted or dampened by the probabilities I assign to the various outcomes.  Those probabilities are rough-and-ready, not at all numeric.  I’m sure I can avoid falling in the river.  I’m almost certain I’ll be able to negotiate the trail hazard safely; but in the unexpected event that I cannot, I will recognize the danger when I see it, and turn back.   The chances of encountering a warden are significant; but the negative emotion attached to that possibility is outweighed by my desire to take the shorter, scenic route.  If I were challenged, I wouldn’t care much.  (But if I saw a warden watching me, waiting for me to step over the rope, the near-certainty of embarrassment might deter me.)

Consciousness is Slow

In several experiments, Benjamin Libet showed that the elapsed time between a stimulus event and conscious awareness of the stimulus is quite long, about half a second.  His results also indicated that, in some cases, the subjective experience is ‘back-dated’ to approximately the time when the stimulus occurred.  You will not be aware of a touch to your skin until half a second after the touch; but when you do, you will have the (correct) subjective impression of having been touched about half a second earlier.  As a result, your memory of the sequence in which things happen, in your experience, closely (although not exactly) matches reality.  But your conscious awareness of events lags considerably behind the events themselves.

Half a second is a long time.  How then do we manage to respond as quickly as we do to events?  Other sources report human reaction time to a touch stimulus to be 155 ms (0.155 seconds).  Typical human test subjects can acknowledge a visual stimulus by pressing a button after 180-200 ms, or an auditory stimulus slightly faster, after 140-160 ms.

There is no single, received interpretation of Libet’s results.  What I will say about them is my own speculation.  My guess is, simply, that a person who is tasked with acknowledging a stimulus as quickly as possible by pressing a button may not require conscious awareness of the stimulus in order to do so.  It may be that he presses the button first and becomes aware of the stimulus later.

Blindsight patients can respond appropriately to visual stimuli which they do not consciously perceive.  Conscious perception of visual images requires signals from the retina to be received in the visual cortex.  They get there via a neural pathway that is relatively ‘new’ in evolutionary terms, and is highly developed in primates.  Blindsight is enabled by an older neural pathway, in which visual signals are received by a primitive part of the brain – the superior colliculus in the brainstem.

Ramachandran asked:

Why do we have an old pathway and a new pathway?

One possibility is that the older pathway has been preserved as a sort of early warning system and is concerned with what is sometimes called “orienting behaviour.”  For example, if a large looming object comes at me from the left, this older pathway tells me where the object is, enabling me to swivel my eyeballs and turn my head and body to look at it.  This is a primitive reflex that brings potentially important events into my fovea, the high-acuity central region of my eyes.  (Ramachandran 1998, p. 73)

Reptiles and amphibians, which have only the older pathway, can respond with alacrity to the visual stimulus of an insect buzzing by, snatching it out of the air.  Perhaps the human subject who is asked to press a button when a light turns green does something similar.  The task is not one which requires the special abilities that consciousness provides.  The subject does not need to weigh pros and cons before coming to a decision; he has already made up his mind how to respond, and only need do so as quickly as possible.  Having formed the intention to press the button when the light turns green, his conscious mind can, effectively, delegate the task to faster subconscious subsystems – and later, observe with satisfaction that the job has been carried out as instructed.

Some have interpreted Libet’s results as showing that consciousness is an ‘epiphenomenon’ – a mere byproduct of the workings of our brains, without a contributing causal role.  That is not my view.  Natural selection does not engender major capabilities which are useless.  A more likely explanation is that consciousness does not do all the work; it is one capability among many that collectively govern human action.

Reason is Limited

Deductive, deliberate decision-making is a paradigmatically conscious activity.  Just as we like to think we are rational, we like to think our ‘conscious minds’ control our behaviour.  But if that is so, it is rather in the way that a CEO is in charge of a large company.  She makes big decisions; she does not (or should not) make small ones.  It is part of her job to detect problems that have grown to a certain magnitude, and to initiate corrective changes of direction.  Of the many actions required for the company’s successful operation, she initiates only a few; but she promotes a corporate culture which favours the right sort of decision-making – which increases the chances that the decisions made by subordinates will help the company succeed.  She should not micro-manage – make her subordinates’ decisions for them – because she cannot attend to their work at the required level of detail.  After all, the CEO is just one person in an enterprise which requires the diligent attention of many.

There is ample evidence that consciousness is just one among many brain functions responsible for governing human behaviour.  The brain functions regulating blood circulation, body temperature and digestion operate almost entirely without conscious awareness, let alone intervention.  Even perception, which is often touted as a paradigm of conscious functionality, happens largely unconsciously, as the example of blindsight shows.

The strength of consciousness is its flexibility. Conscious responses are innovative in ways that innate instinctual responses and learned habitual responses are not.  Using consciousness, we can think about the unique elements of a problem and devise a solution appropriate to its uniqueness.  Consciousness can introduce disparate scraps of knowledge, which may have been acquired over a long time from different sources and through different sensory modalities, into a common arena; it can juxtapose them in new ways and extract new meaning, in order to guide our behaviour in creatively productive ways.  An invention like the credit default swap – a way of insuring and repackaging subprime mortgages and other risky loans into triple-A-rated securities which can be sold for obscene profits – would never have occurred without consciousness.  A more mundane (and benign) example is route-planning.  This afternoon I want to: buy fish and fresh produce, drop off my shirts to be laundered, shop for a new toaster, and take a stove part to a machine shop to have a hole drilled.  I place my five stops on a mental map of North Vancouver, then plan a trip which will take me to all of them, comfortably within the business hours of all five establishments concerned, via a route that minimizes the overall distance travelled.  Consciousness performs this task for me.

Consciousness is often a passive observer of behaviour.  When I drive a familiar route, I typically do so on ‘auto-pilot.’  I am usually aware of my present location, but not always.  I have had the experience of being so distracted by other concerns that I briefly lost my orientation; I ‘woke up’ and realized I didn’t know where I was on my route – whether on Queens or Highland – and I needed to find a landmark to answer the question.  Ingrained habit can get me to and from work in a car.  Until something unexpected happens, consciousness does not intervene.  Its role is similar to that of a driving instructor alongside an advanced student in a car with dual controls; mostly just monitoring, occasionally giving a course direction, rarely if ever taking the wheel.

According to Damasio, our emotional responses to imagined alternative outcomes are a necessary adjunct to rational decision-making.  Neurological patients whose emotional centres have become disconnected from executive centres in their brains are unable to make choices that will help them reach prudential goals.   Their impairment effectively prevents them from acting in their own interests.

The Neurological Evidence

Descartes’ Error begins with the strange case of Phineas Gage, a railway foreman who, in 1848, had an accident in which an iron tamping rod, over three feet long and 1 ¼ inches in diameter, passed through his skull, destroying portions of his prefrontal cortex, mostly on the left side.  Remarkably, Gage never lost consciousness, and was able to sit up and answer detailed questions about the accident while receiving medical treatment an hour later; even more remarkably, he made what appeared at first to be almost a full recovery.  He had no paralysis, no impairment of speech or language; only blindness in his left eye.

Soon, however, his behaviour changed.  In the words of his physician, John Harlow, he was “fitful, irreverent, indulging at times in the grossest profanity which was not previously his custom, manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operation, which are no sooner arranged than they are abandoned.”  These character traits were all new; Gage had previously been responsible, persistent and shrewd, valued by his employers, who judged him “efficient and capable”.  Soon after Gage returned to work, the railroad let him go, for he could no longer by relied on: “Gage was no longer Gage.”  Gage’s remaining history, until his death in 1860, was marked by sporadic and unsuitable employment, offensive behaviour, and poor choices.

In 1994, using a reconstruction of Gage’s skull and computer simulation, Hanna Damasio determined that the damage to his brain included the ventromedial region of the frontal lobe, a region known to be involved in planning for the future, observing rules of social conduct, and prudential decision-making.

Descartes’ Error then turns to a contemporary case, one of Antonio Damasio’s own patients, ‘Elliot,’ who also suffered ventromedial frontal lobe damage, as a result of a tumour and subsequent surgery.   Like Gage, Elliot underwent personality changes.  From being a responsible husband, father, and employee with “an enviable personal, professional and social status,” he lost all motivation: he needed a push to get up in the morning, lost all sense of the relative importance of tasks at work, and could no longer be trusted with a schedule.  He soon lost his job, and started various ventures, from home-building to investment management, that soon failed.  He lost his savings, then his wife and family, then a second wife.   Instead of being made miserable by these setbacks, Elliot seemed indifferent.  He told Damasio that

his own feelings had changed from before his illness.  He could sense how topics that once had evoked a strong emotion no longer caused any reaction, positive or negative.  (Damasio 1994 p 45)

In tests of intelligence, memory and other cognitive functions, Elliot performed at or above average.  He struck Damasio as “coherent and smart,” well versed in current affairs, and unimpaired in business knowledge.  He easily passed a raft of psychological tests designed to reveal frontal lobe impairment.  When asked to think up appropriate responses to social problems (for example, how to defuse a spouse’s anger after breaking her favourite flower pot) or to consider the consequences of actions (such as what would likely happen if he were to pocket an overpayment given in error by a bank teller), Elliot performed as well as, or better than, controls.  Yet while considering his above-average performance in thinking about such scenarios, he commented, “And after all this, I still wouldn’t know what to do!”  His only impairment seemed to be one of motivation.

Elliot became one of the frontal-damaged subjects in the ‘Gambling Game’ experiments conducted by Damasio, Tranel, Bechara and others, which were described in an earlier Phantom Self post.  Damasio cites these as his main experimental evidence for his hypothesis that emotional ‘somatic markers’ are the indispensible cornerstone of rational behaviour.

In these experiments, frontal-damaged patients and normal subjects were asked to choose from four decks of playing cards.  Whenever a player selected a card, he was rewarded (in play money); a few cards also triggered penalties.  Two of the decks paid out $100 rewards, the other two $50; however, the $100 decks were stacked against the players with high, although infrequent, penalty cards, whereas the $50 decks had on average lower penalties, and were biased in the players’ favour.  Both normal and damaged players were initially drawn to the $100 decks.  After drawing a few punishment cards, the normal subjects began to show elevated GSR’s when selecting from the $100 decks. The patients with frontal damage showed no change in skin conductance.  A little later in the game, normal subjects began to avoid those decks, even though they reported having no idea which decks were better, but the damaged patients continued to prefer the $100 decks.   Towards the end, after turning 80 cards or so, most of the normal subjects, and three of the six damaged ones, cognitively ‘figured out’ the bias in the decks.  By that time, all the normal subjects showed a strong preference for the ‘good’ decks.  None of the frontal-damaged subjects did so – even the three that knew the bias.

It is hard to understand what went on in the minds of those three, who had figured out the game, knew intellectually how to beat the odds, were trying to win, and yet continued to choose from the ‘toxic’ $100 decks.  What were they thinking? Damasio suggests that cognitively, the damaged patients were like the rest of us – given enough evidence, they could assess probabilities of future outcomes with some accuracy.  But because they failed to generate somatic markers – emotional associations, which could “start operating as an alarm signal” – the ‘significance’ of those imagined outcomes would not be apparent to them, and would have little or no influence on their decision-making.

When Does Rationality Fail?

We are dogged by uncertainty in our daily lives.  Most of our decisions must be made on the basis of imperfect information.  This is especially true in social situations; we rely on rough assessments of likelihood, and how we feel about the people we’re dealing with.  We would have difficulty supporting those hunches and feelings by strict rules of evidence.  Logic and calculation play a minor role in our deliberations.  We constantly assess probabilities without any calculation.  This is useful, because most people are bad at recording and analyzing statistics, and calculating probabilities.  Emotional associations allow us to make our way effectively in an uncertain world.

Not perfectly effectively.  Some of our biases are measurably irrational.  Many people fear flying more than driving, although they know that statistics overwhelmingly favour flying.  That may be partly because we are the drivers, and we think our driving performance is much better than average.  (Assessing one’s own performance as above average is a recognized cognitive bias known as illusory superiority.)  Or it may be because the probability of surviving a car accident is higher than the probability of surviving a plane accident.  Or the bias may be rooted in the fact that in a car, we have some control over the situation, compared to a completely passive airline passenger.  (Even a passenger in a car is not wholly passive; he can notice danger and alert the driver.)

If normal rationality depends on emotional responses, some of which are innate, others learned over a lifetime, then we should expect rationality to be ill-prepared if the world changes in certain respects.  We may be unable to choose ‘rationally’ – i.e. in ways that maximize our most deeply-held values – in situations which do not push our emotional buttons in the right ways.

Perhaps one reason we have failed, so far, to respond effectively to the threat of global warming is that the emotional responses we have learned in our lives so far are a poor fit to what is happening.  (1) We have never before had to respond to a threat on a global scale.  Our customary military and trade alliances do not fill the bill.  And the danger is not like others to which we have learned to respond, such as military, trade, or economic threats.  (2) The process is too gradual, and masked by the noise of seasonal and weather variations, to be noticed perceptually.  If we are to be convinced of its reality, we must trust measurement instruments, scientific records, and statistical analysis, none of which are key decision-drivers for most people.  (3) So far, the signs and symptoms of global warming are, as often as not, pleasant ones in the dominant, developed areas of the world, which is where effective action must begin.  Although we have experienced devastating hurricanes and pine forest die-offs, we also see less snow and warmer summer days, which by and large are welcomed.  Global warming has not yet been associated with visceral, negative emotional markers in most people’s personal experience.   On this hypothesis, we are emotionally blind to most symptoms of man-made global warming, and therefore it will likely continue to have little effect on our decision-making – until things get much worse.  If forced to choose between global warming and a big, truly motivational carbon tax (levied on transportation and home heating fuels, on electricity from coal-burning plants, etc.), the negative emotional response of most voters to higher prices will outweigh that associated with global warming.  This may go down in history as a very serious failure of a democracy.


Damasio, A.R. (1994), Descartes’ Error

James, William (1890), The Principles of Psychology

Libet, Benjamin (1985) “Subjective antedating of a sensory experience and mind-brain theories: reply to Honderich” (J. Theoretical Biology, vol. 114, pp 563-570)

Ramachandran and Blakeslee (1998), Phantoms in the Brain

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