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10 February 2016

NeuroLogic: The enthralling story of the unconscious mind

We may have a complex, scientific take on the unconscious mind, but as Eliexer Sternberg's new book shows, explanations demand a nuance befitting the subject

Habit of mind: driving a route daily becomes mostly automatic

Paulo Pellegrin/Magnum Photos

“THE conscious mind may be compared to a fountain playing in the sun and falling back into the great subterranean pool of subconscious from which it rises,” wrote Sigmund Freud. For him, the unconscious/subconscious (he used the words interchangeably at first) played an outsized role in governing human behaviour. We are enthralled by the idea that we aren’t privy to most of the mental processes that make us human.


In 2016, the idea of the unconscious mind is still enthralling, but in a very different way. The neurology and cognitive science that has replaced psychoanalytical notions with evidence-based ideas demands constant revision and is nuanced and complex. So any book trying to bring us up to speed must do so with restraint, even as it attempts to excite and entertain.

Eliezer Sternberg, a neurologist at Yale-New Haven Hospital, has a stab at elucidating the power of the unconscious from the scientific perspective of the 21st century. In NeuroLogic, he tells us where we are now: “The unconscious system in the brain pieces together fragments of our perceptions, anticipating patterns and filling in gaps when necessary… to devise a single, meaningful interpretation. It tells a story. The conscious system experiences that story but can also reflect on it and question it.”

Understandably, Sternberg focuses mainly on conditions that give rise to seemingly irrational perceptions and behaviours, but which make sense in terms of a compromised unconscious. For example, people who are fully or partially blind can sometimes experience vivid visual hallucinations. This is Charles Bonnet syndrome, where the visual cortex can occasionally become active despite a lack of signal from the eyes, possibly because neural signals “leak” in from other brain regions.

For avid readers of popular neuroscience, much of this will be familiar as Sternberg dips into a grab bag of neurocuriosities. Those newer to the field will be intrigued, say, by blindsight, in which someone unconsciously responds to a stimulus while denying having seen it, or alien hand syndrome, where damage to the brain’s frontal lobe can result in losing control over the actions of, say, your right hand.

For me, as a relatively informed reader, the most intriguing part of NeuroLogic is when Sternberg writes about how consciously learned behaviour can become habitual: “There are two parallel systems in the brain that control behavior. When we practice a behavior enough, we can automate it, allowing the habit system to take over. This frees up the conscious, non-habit system to focus on something else.” For example, the complex activity of driving a car requires vision, touch and exquisite motor control. But it can become mostly unconscious when the driver takes the same route day after day.

Why did both the conscious and unconscious systems evolve? Sternberg doesn’t say so explicitly, but his way of delineating brain activity suggests one reason we may have evolved consciousness: to shoot down illogical stories concocted by the unconscious – which he calls an “egocentric storyteller” – that can get things wrong when the neural circuitry goes haywire.

Can the conscious right some of these wrongs? Can it influence the unconscious? Yes, says Sternberg: “Mental simulation is a means by which the conscious system can change the unconscious system.” Take the British athlete Steve Backley, a bronze medallist in the javelin at the 1992 Barcelona Olympic games, who sprained his ankle just before the 1996 Atlanta games. He was on crutches for weeks, so he trained by imagining the perfect throw over and over again. He won silver that year.

NeuroLogic sometimes feels like a series of well-written magazine articles, drawing mostly on academic case studies that are once-removed from real people and their stories. This can make the writing a bit distant, especially when the conditions described are harrowing. But occasionally we get a ringside seat, as when Sternberg describes his friend Ethan’s visceral fear on being “attacked” by an imaginary falcon conjured up by a stage hypnotist.

“The unconscious system in the brain pieces together fragments to devise a meaningful interpretation“

In trying to make his case for the conscious and unconscious, Sternberg sometimes fails to use the nuance necessary to fully grasp complex conditions or neural processes. For example, he omits recent insights into possible neurocognitive mechanisms behind Cotard’s syndrome, a disorder in which people think they are dead. And then there are mirror neurons, which studies in monkeys show fire when an animal observes the action of another. Sternberg leaves us with the impression that there is little or no controversy about their existence in humans and about claims linking them to everything from empathy to culture.

It’s a useful reminder that in this fast-moving, complex field, nuance is everything.

This article appeared in print under the headline “The brain’s deep secret”

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