The Body Electric

We are juiced. From head to toe, miles of membrane shuttle electric charges through the body. Impulses pour in to the brain from eyes, ears, nose, mouth, and skin as electric translations of what I see on this screen, the feeling of the keys at my fingertips, the tapping sounds; then out from the brain through the wires to the muscles in my hands and fingers to type the s e  l e t t e r s.

Simple nerve systems appeared in early jellyfish and other sea creatures about 500 million years ago.  Loose nets of nerves responded to light and the touch of other creatures as these swimmers captured smaller fish and dodged bigger ones.

Much earlier, in the first fully developed cells, neurons began to evolve from membranes. A membrane, in Wikipedia’s words, is “a selective barrier; it allows some things to pass through but stops others.” A cell’s membrane helped the cell manage the salt levels inside the cell as it floated through the salty ocean. And since the salts of sodium, potassium and calcium consist of atoms with a positive or negative charge, the pores in membranes became gates that opened and closed to control the electrical potential across the membrane itself.

As animals evolved, such membranes lengthened into neurons with conductive axons, the “wire” of the nerve cell. In us, the longest axon runs down the length of each leg, branching as it goes. The shortest axons, fractions of a millimeter, fill our heads by the billions.

Neurons in the brain (Wikipedia)

Neurons in the brain
(Wikipedia)

The axons don’t carry an electric charge in the way that a wire carries electricity or a lightning bolt of electrons crashes to the ground. Instead, think of the wave at a sports stadium, where groups of fans stand up, throw their hands in the air, and sit down in a spontaneous sequence that moves through the rows. A nerve impulse moves down the axon in a similar way, charged atoms crossing through opened pores from one side of the membrane to the other and then quickly back again while the “wave” of the electric charge moves along.

The impulse never varies in strength. It is either on or off, moving or only ready to move. There are no drops in the current, no power failures, no biological surge protectors needed. If a muscle must contract to move a load, the nerve signal, always at the same strength, simply repeats rapidly enough so that the muscle cells remain contracted.

At both ends of the axon, where the impulse begins and ends, devices of various kinds translate between the electrical charge and other structures. In the ear, sound waves cause small hairs to vibrate and set off the impulses that we hear as “hello.” In our eyes, light causes molecular changes that trigger the impulses to the brain to form the image we recognize as a chair. Where a neuron terminates at a muscle cell, the final “wave” triggers chemicals that start the muscle’s contraction.

We barely notice all this wizardry. Compared to the breath that we can feel and the blood we can see, our circuitry is undetectable. But if we’ve been shocked by a faulty toaster or we suffer from numbness or irregular heartbeats, we’ve glimpsed what can go wrong.

In another way, though, we are always aware of the electricity in us. Notice the faint tingle that is always present in our limbs and head. It’s a sense of animation, a potential, an ability to move a muscle, look around or think a thought at any time. That tingly readiness is, essentially, our neurons at the ready. It’s a reminder that we’re alive.

The Gambler’s Fallacy and Other Biases of the Brain

If you’re feeling cynical about people and our foolish ways, a place to go to buttress your mood is Wikipedia’s List of Cognitive Biases. It describes more than 150 ways in which our thinking systematically deviates from objective observation and rational thinking. It’s a humbling list, a reminder that the evolution of our brains has left us with some thought processes that, though useful in certain situations, don’t make it easy for us to see the world as it actually is.

Here’s a sampling. Quotations are from Wikipedia.

Gambler’s Fallacy: “I’ve flipped heads with this coin five times consecutively, so the chance of tails coming out on the sixth flip is much greater than heads.” No, it’s not. The odds are 50-50 for every flip, regardless of the length of any previous sequence that produced one result. Applicable to apparent batting slumps and other so-called streaks of good or bad luck or performance.

False Consensus Effect: “The tendency for people to overestimate the degree to which others agree with them.” I’m sure you’ve all found this to be true.

 (io9.com)

(io9.com)

Actor-Observer Bias: If you cut me off in traffic, you’re a complete jerk. I blame you and your rotten personality. But if I make a quick turn in front of you, I had good reasons for doing so and my character remains untarnished. On the whole, we’re not very perceptive about our own characteristics and motivations—or those of other people. We are, however, for evolutionary reasons, quick to identify whatever might be a threat and attribution errors create plenty of misunderstandings and conflict.

IKEA Effect: “The tendency for people to place a disproportionately high value on objects that they partially assembled themselves, such as furniture from IKEA, regardless of the quality of the end result.”

Illusion of Truth Effect: “A person is more likely to believe a familiar statement than an unfamiliar one.” Perhaps this has been a safety measure for our species in the long run.

Reminiscence Bump: “The recalling of more personal events from adolescence and early adulthood than personal events from other lifetime periods.” Perhaps the vivid imprinting of our first mistakes and successes has helped us survive. In general, our memories are biased towards thinking highly of ourselves.

Illusion of Transparency: “People overestimate others’ ability to know them, and they also overestimate their ability to know others.” Such overestimating gives us confidence about forming social bonds. If we were realistic about how difficult it is for one person to know another, we would be less likely to go to the trouble or take the risk.

These and other biases have either served our species in the distant past or result from the brain’s limited processing capacity. Since they won’t go away anytime soon, we have to compensate for them as best we can. Wisdom often amounts to an effort to do just that: if we strive to be humble, nonjudgmental, and cautious, our cognition may be more on target.