The Limits of Rational Thought

A couple of months ago a friend of mine recommended I pick up Richard Power's new novel The Echo Maker. "It's right up your alley," he said, "It's all about a man suffering from a bizarre brain condition." I added it to my Amazon shopping cart within the hour.

In The Echo Maker, Powers' character Mark flips his truck on an icy stretch of road in Nebraska and ends up in the hospital in a near-vegetative state. His sole-remaining family member, his sister Karin, immediately rushes to his bedside to nurse him back to health. Mark remains comatose for long enough that the doctors begin to lose hope. But then, miraculously, he wakes up. It takes him weeks to regain the power of speech, but once he does, it becomes clear that something is seriously amiss: Mark is convinced that this person who hovers by his bedside at all hours of the day, who looks and sounds just like his sister, is a plant--an imposter sent to surveil him and report back to "the authorities."

Powers soon reveals that Mark is suffering from a condition known as Capgras Delusion, which just so happens to be my favorite neurological condition. Once thought to be undeniable evidence of psychosis, Capgras Delusion is now believed to be a neurological syndrome caused by faulty wiring between the two areas of the brain involved in facial recognition: the temporal lobe, which contains pathways specializing in identifying faces, and the limbic system, which is responsible for attributing emotional significance to these faces.

You may be wondering what fuels my fascination with such a bizarre mental disorder - and I won't lie: morbid curiosity plays a large role - but another reason I find Capgras Delusion so intriguing is that it gives us some insight into the limits of rational thought.

Human beings tend to think of the brain as the body's chief executive and rational thought as the predominant force in our daily lives. Some of us grudgingly admit that the subconscious plays a role, but we waste little time contemplating what that role is outside of the confines of our therapist's office. In our daily lives, we cleave to the belief that our logical brains are in the driver's seat. Occasionally, the Id rears its ugly head - prompting us to eat half a pecan pie, drink more than the recommended dosage of red wine, or tumble into bed with an attractive stranger - but by and large, we're able to curb these impulses and let reason guide us. Right? Not necessarily. Our decision-making processes are dictated by a number of "irrational" factors and Capgras Delusion is the perfect example of how these factors can short circuit the logical mind.

When we encounter a face, two things occur in the brain. Our visual centers survey the physical attributes of the person in front of us and match them up with a template stored in the temporal lobe, thus allowing us to classify the person. This information then gets transmitted to the limbic system, which conjures up the appropriate feelings.

People suffering from Capgras Delusion only experience the first half of this process. Because their temporal lobes are in tact, they recognize that the person standing in front of them looks exactly like their mother, but this recognition evokes no emotional response. The way the brain copes with this disjunction is by making a logical leap: 'This person looks like my mother, but doesn't feel like my mother, therefore she must be a fraud.'

Now if the person suffering from Capgras was unaware of his impairment, this response would be entirely understandable. What's really mystifying is that explaining what's happening makes absolutely no impression on the patient. No matter how many times he's told that he's suffering from a neurological condition, he will persist in believing that he's being hounded by doppelgangers. If the rational brain was at the reins, it stands to reason that the patient would accept his doctor's explanations. But when it comes to Capgras Delusion, emotions trump logic. The mind simply cannot accept the idea that a spouse, a mother, or beloved sister elicits no feeling, so the delusion persists.

People often assume that allowing emotions to color their decision-making process is a mistake - and in the case of Capgras Delusion, it is - but this is the exception to the rule. As Jonah Lehrer, the brain behind Science Blogs' The Frontal Cortex, noted in his recent lecture "Walt Whitman's connection to modern neuroscience," emotions are essential to healthy functioning. We hyper-rational denizens of the modern world are in the habit of overestimating the importance of logic, but without emotions, the rational mind is entirely incapacitated.

In this fascinating lecture, Lehrer argues that recent scientific findings have proven that Walt Whitman was correct in his assumption that the body and the mind are of a piece. As evidence, Lehrer cites the research of famed University of Iowa Neurologist Antonio Damasio. Damasio spent years studying patients who couldn't generate emotions because they lacked the brain regions necessary for interpreting physical sensations, like the pounding of the heart. These emotional invalids suffered from myriad problems, but their most marked feature was an inability to make even trivial decisions. As Lehrer says:

Damasio's emotionless patients proved incapable of making reasonable decisions . . .They would literally sit there for three hours in the morning trying to choose between Cheerios or Honey Nut Cheerioes. And Damasio's conclusion is that unless you have the emotional inputs, you can never evaluate between the logical possibilities.

Whitman once said that, "If our consciousness was severed from the body, there would be no mind stuff left behind," Lehrer tells us, and modern neuroscientists are beginning to concur. We in the West have been weaned on the notion that rationality is paramount, but it's time to relinquish the idea that the logical mind can operate independently. As Damasio once said "rationality is actually intimately connected with emotions." We need to take a page out of Whitman's book and place more trust in our instincts.

Unconvinced? Take a look at this recent study conducted by researchers at University of College London, which found that "instinctive snap decisions are more reliable than decisions taken using higher-level cognitive processes."