The reptilian brain: the new left brain, right brain?

Over the past couple of weeks I have heard a number of different people on the radio – a scientist in one case, psychologist in another – talk about our intuitive brain, our reptilian brain, our emotional brain as if it were a separate entity within our brain. Slightly surprised by this idea, I decided to look at it in a bit more detail – surprised because my conception of the brain as someone who has studied it is that of an integrated, unified entity in which different regions throughout are working together in order to perceive the world, make sense of it and act in it appropriately. The idea of the existence of a special system dealing with our emotions and intuitions seems counterintuitive in a system where every single part works together with other parts in order to think, act, memorize, speak.

We like to believe that the decisions we make, the actions we take and, at least sometimes, the thoughts we have are based on rational weighing up of pro’s and con’s. Equally, I think that most of us would admit that at times we do things because our gut feeling tells us to do so. This idea is not a new one; even Aristotle suggested that a logical decision can be overturned by mere appetite for pleasure or anger. But even if there is the existence of gut feeling alongside reason, does this mean we have a separate set of brain regions to deal with our different states of mind?

According to a number of researchers, it does. Several groups of prominent neuroeconomists, such as Douglas Bernheim and Antonio Rangel, have proposed models that describe the brain as operating in a “cold” deliberative mode or a “hot” emotional mode, depending on the situation in which a decision is being made. Based on the anatomical structure of our brains, back in the 1960s Paul MacLean proposed the influential theory that we have a ‘triune’ brain consisting of three parts, each formed at a different time in evolution. In essence, he too argued that our brains contain ancient reptilian fight or flight mechanisms, animal instincts and emotions, and new thoughtful cortex to offset these other urges.

While some of these principles are generally accepted, the existence of entirely separate systems underlying emotional, intuitive impulses on the one hand and rational considered behaviour is more controversial. Nonetheless, the notion of a direct anatomical basis for separate intuitive and rational systems seems to have caught the public imagination. A quick Google search on “reptilian brain and decision” brings up numerous self-help and business-based writings about how to tame your reptilian brain, live with your emotional urges and stop it buying your Starbucks lattes.

It doesn't seem too long ago to me that another dichotomous idea from neuroscience, that the two halves, or hemispheres, of our brain have highly specific functions, was providing this market with these metaphors. Again, the science suggested (not without challenge) that left part of the brain was the dominant linguistic side, cold and calculating and dealing with details (the cognitive side) whereas the right was the imaginative but suppressed side that dealt with the global processing of information and emotions (the intuitive side). And again, this spawned a large industry of self-help and business books on everything from how to unshackle your right hemisphere in order to become more imaginative and even to help us get in touch with the opposite sex.

Looking at the persistence with which ideas of a separation between intuition and reason have popped up in the past and present, is it likely whether these theories will ever fade? Or does our hunger to become a better person – more creative or more logical – make us embrace the idea of separate systems because we feel they give us (false?) opportunity to enhance certain qualities in ourselves to make us into the person we want to be?

I wrote this article for 'Matters Scientific', the science blog of Cherwell, the Oxford University student newspaper.