Sunday, 13 November 2011

The Decisive Moment

So Roo said to me that after reading Michael Shermer's The Believing Brain I should read Jonah Lehrer's The Decisive Moment: How the Brain Makes Up Its Mind.  I always aim to please and I did enjoy Shermer.

Lehrer is one of those annoying people who seem good at lots of things.  He has a degree in neuroscience, studied literature and theology at Oxford as a Rhodes Scholar, and writes for a number of different publications.  Where Shermer is a scientist who writes, Lehrer appears to be a writer who does science.  He is less technical than Shermer, more journalistic and accessible.

The Decisive Moment (apparently marketed in some countries as How We Decide) covers a lot of the same territory as The Believing Brain, including reporting many of the same experiments.  However, Lehrer asks a different question to Shermer and so of course he gets a different answer.  Shermer is interested in belief, and his conclusion is that we should reject the emotional, unconscious part of our mind and form our beliefs using our capacity for rationality, aided by the stringent methodologies of western science. 

Instead of the "big" questions posed by Shermer, Lehrer is interested in a practical issue - what is the best way for us to make decisons?  He talks about the model of rationality first outlined by Plato, in which our reason is the charioteer, driving and guiding the horses (often wild and difficult to direct) of our emotions and impulses.  This ideal has influenced Western thought from Plato onwards (including, obviously, Shermer), but according to Lehrer it is a mistake.

To illustrate the point he tells the story of a man who has his orbito-frontal cortex - one of the key brain areas processing our emotions - destroyed by a brain tumour.  Although his intelligence is unaffected, he is almost completely unable to make even the most simple decisons, like what to have for dinner or where to park his car.  He intensely compares and analyses his options, but never reaches a conclusion.

From here Lehrer spins a vivid tale of how our brains make decisions.  To summarise what is a complex and absorbing tale (or set of tales), it goes something like this.  Our rational brains are good at computing.  They do numbers and measurements, and compare objective elements of our various choices.  They keep a check on our emotions, and allow us to avoid obvious, silly mistakes.  However, these same rational brains are easily deceived.  They are only able to deal with about seven variables at once, and get easily overloaded.  They are also not good at aesthetic decisions.  Thus, people asked to rate a set of posters - some with classic artworks, some with funny cats - will almost always choose the classic art.  Yet if they are asked to explain the reasons for their choice before choosing, many more of them will choose the funny cats, even though they regret it later.  Their reason gets in the way of their better judgement.

So what to do?  Well, for Lerher the brain is something like a committee meeting.  Our rational mind will add up figures and caution us about factuality.  The pleasure centres of the brain will flood us with dopamine when we consider a choice that appeals to us - even though there may be no obvious rational explanation.  The pain avoidance centres will likewise flood us with apprehension when we consider things that appear unpleasant.  We need to listen to all of these things to make good decisions.  Counter-intuitively, the more complex a decision, the more we need to trust our emotions and the less we can rely on our rationality.  We can reason our way to choosing the right vegetable peeler, but if we are buying a house or a car we need to trust our emotions.

So if Lehrer and Shermer were in a room together and discussing how to decide what belief system to follow, what would they say to each other?  I can't find that this scenario has ever been played out, at least not in public, but perhaps it would go like this.  Shermer would say that our emotions and our unconscious impulses are not to be trusted because they are biased.  Therefore they need to be overridden by evidence.  Lehrer might reply that the matters under consideration are so complex that our rational minds can't cope with the number of variables, and that listening to our emotions will help us to make better decisions about these things. 

Shermer would respond, perhaps, that our emotions are tutored by our environment and our upbringing, so that if we have consistently been taught something that is factually incorrect, hearing it will produce pleasure. Lehrer would agree that the debate in our brains needs to involve all parties and that sometimes our fear at abandoning treasured ideas needs to be overridden by rationality.  But at other times, when the answer that appears so rational nevertheless makes us feel sick in the stomach, then perhaps our emotions are pointing us to something beyond the comprehension of our reason, and we would be foolish to ignore it.

Aristotle apparently described humanity as a "rational animal".  Jonathan Swift begged to differ, describing us as "an animal capable of reason".  Lehrer seems to suggests it's not so simple.  We are indeed capable of reason, but reason may not be all its cracked up to be.

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