The Shallows: Chapter 2 Summary & Analysis

To explain how tools affect our brains, Carr opens with an anecdote about Friedrich Nietzsche. When the philosopher switched from pen and paper to a typewriter, he noted that his writing became more forceful and staccato. “Our writing equipment,” commented Nietzsche, “takes part in the forming of our thoughts.” Nietzsche’s observation suggested that brain function actually changed in response to our tools, a view that was not accepted in his era. Carr notes that psychologist Sigmund Freud expanded this new theory of the brain in his early career as a neurophysiology researcher. Contrary to the pervasive view that the brain was a continuous fabric, Freud suggested that the brain had a cellular structure with gaps, also known as synapses. Modern scientists now know that the brain is, as Freud suggested, made of a network of neurons that transmit electric pulses through the spaces that divide them.

It took lots of time and research to overturn the false belief that the brain, once formed, was a fixed organ. Carr, accounting who helped change this belief, cites the work of Michael Merzenich. Merzenich studied monkeys with nerve damage in their fingers. When one part of the injured monkeys’ hands were touched, the signal became confused on the way to their brains and they believed a different part of their bodies was being stimulated. However, the monkeys eventually repaired this mental confusion on their own. His study suggested that neural pathways in the monkey’s brain reorganized themselves to reflect the new map of nerves in their hands. This concept of the brain’s plasticity––or ability to change––is called neuroplasticity.

Scientists in the early 20th century remained skeptical, however, sticking to the idea of the brain as a mechanical and fixed organ. The prevalent idea was that the “vital paths” of the brain were laid in childhood and remained fixed upon maturation. The machine-brain point of view was solidified by the past attitudes of the Enlightenment, a historical age in human development when reason and science were heralded over emotion. The result of this prevailing view was that consciousness–-or the idea of a mind separate from the brain––was seen simply as a byproduct of the machine-brain.

As science advanced, the argument for plasticity slowly strengthened. Carr cites the work of biologist Eric Kandel, who performed a study on sea slugs in the early 1970s known as the Aplysia experiments. Kandel found that if you touch a sea slug’s gill repeatedly without causing the animal harm, its original reflex to recoil lessens. The slug, through repetition, learns that it won’t be hurt. This concept gave rise to the scientific saying known as Hebb’s rule: “Cells that fire together wire together.” In other words, repeated physical actions can reroute our brains.

The concept of neuroplasticity united two differing philosophies on the nature of mind: empiricism and rationalism. Empiricism, exemplified by philosopher John Locke, is the belief that we are born with a blank slate and that our experiences mold our minds. This can also be understood as the “nurture” argument. Rationalists like Immanuel Kant, on the other hand, hold that we are born with templates that determine how we think. The presently accepted view of the brain as plastic––or capable of change––encapsulates both. We are born with “templates,” or a genetically determined basic brain structure, but our synaptic connections are shaped by our various life experiences. Neuroplasticity combines both the “nature” and the “nurture” argument.

Much of the evidence for neuroplasticity comes from studies on the brain’s reaction to both physical and mental experiences. Phantom limb syndrome––in which an amputated limb is perceived as still attached––is the result of the brain being in the midst of reorganizing itself to match the body’s new state. Purely mental activity can have the same effect, as seen in cab drivers in a 1990 UK study. The area of cabbies’ brains responsible for storing spatial representations was far larger than average. While our DNA might determine a basic outline at birth, the process of living––as seen with the sea slug, the monkeys, the cab drivers––continually organizes and reorganizes our brain’s structure. The problem, notes Carr, is that the brain doesn’t discriminate when rewiring. While plasticity gives us an out from having a brain determined in childhood, the rewired habit or reaction can just as easily be unhealthy––a behavioral loss, rather than a behavioral gain.

Digression. The ancient philosopher Aristotle believed many strange things about the brain. He believed it was a cooling mechanism, that humans have the largest brains because our hearts are the hottest of all animals, and most importantly for Carr’s digression, he believed that the brain had nothing to do with sensation because “when it is touched no sensation is produced.” Carr’s point is that Aristotle’s mistake is understandable. All of our other organs are perceptible to us because they are separate from the organ that perceives them. The question becomes, then, how do we learn about something with no level of remove? How can we think about thinking, if at all––or is the nature of consciousness forever out of consciousness’ grasp?

The philosopher Descartes, two hundred years later, wrestled with the same idea. He compared the brain to a “machine” similar to the ones that operated royal fountains. While the heart pumps blood, the brain pumps spirit. Modern science has wiped out what now seem like silly ways to think about the brain. However, Carr points out that humans still want to believe that something about the brain remains impervious to our understanding. It’s more comfortable to believe that our experiences don’t imprint themselves on our brain structures. “To believe otherwise,” he writes, “would, we feel, call into question the integrity of the self.”