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Attention!

We live in a world of bewildering complexity. There is just far too much going on for us to be aware of all the sights, sounds, smells, tastes and touches that constantly harass our senses. Our brains have therefore evolved to select some aspects of the world for mental processing and ignore the rest. That process is what we call attention.

Its selective nature is easily demonstrated. In one famous example, people are shown a video clip of a basketball game, and are asked to count how many times the ball is passed by the players. People are generally so intent on watching the players and counting the passes that they fail to notice a person dressed in a gorilla suit walking through the scene. Similarly, if you play two different messages simultaneously into each ear via headphones and ask people to listen to one of the messages, they generally fail to pick up any information from the other, even though it’s equally loud. This proves that attention can be operated internally, by the mind, and not simply by orienting the ears. Visual attention, though, generally depends on where the eyes are looking. Even so, it is possible to look straight ahead and yet pay attention to events out of the corner of the eye—a device that can be used by rugby or netball players to trick the opposition. Or by school teachers, anxious to detect mischief-makers.

Nature has equipped us with automatic mechanisms to capture events that might be important for survival. Loud noises, sudden movements, brilliant flashes of light—these all divert us from what we are doing, in case they signal danger. So does extreme pain. A severe toothache, for example, may divert us from reading an assignment—although equally we might indulge in some especially engaging activity, such as listening to a favourite band, to take the mind off the pain. Alarm systems are typically loud and jarring, although we may also be tuned to more subtle events. A mother may be especially alert to the sound of her baby crying, even from a distance, and all of us are sensitised to the sound of our own names being spoken, even when whispered.

We are not slaves to the environment, though; attention can be controlled voluntarily, as when we choose to read a book, listen to a lecture or a piece of music, or solve a crossword puzzle. To a degree, then, we can filter out most environmental distractions, although not all. In his poem ‘The Canonization’, poet John Donne famously exclaimed ‘For God’s sake hold your tongue, and let me love’. Attention is not always directed to the external world. We can beam it inwards, as when we are lost in thought or reverie.

Attention requires a fine balance between concentration on the task at hand and awareness of the surrounding environment. We cannot be so intent on solving a Sudoku puzzle that we fail to observe the conflagration around us, nor can we be so distractible that we fail to complete any task requiring sustained concentration. Sometimes the balance is disturbed. People with damage to the frontal lobes often have difficulty shifting from one task to another, or in adapting to changes in instructions. This suggests that the frontal lobes are the drivers of attention. People with attention deficit disorder have the opposite problem, they are too easily distracted. In general, boys seem more prone to this than are girls and there may be an evolutionary reason for this. In a hunter-gatherer society, it was probably the males who did the hunting, and hunters should pay attention to all distractions—that noise to the left may be a hungry lion.

An example of the effect of hemineglect in a sketch by Lovis Corinth

The human brain is curiously asymmetrical in the way it controls attention. The left brain attends to the right side of space; the right to both sides, albeit with some bias toward the left. Damage to the right side may therefore cause a patient to lose awareness of events on the left, a phenomenon known as hemineglect. The patient may eat from only the right side of their plate, dress only the right side of their body, ignore those who address them from the left, and are easily beaten at chess by attacking on the left flank. A famous example is the German artist Lovis Corinth, who suffered a right-brain stroke in 1911 but continued to draw and paint until his death fourteen years later. Much of his work shows a neglect of the left side, as in the portrait above.

Just why the brain should function in this asymmetrical way is not clear. Perhaps it’s because in most of us the left side of the brain is largely taken up with language, and so loses some of its capacity to direct attention to space. Left-brain damage seldom results in neglect of the right side, or does so only transiently, and there is no evidence that non-human animals show a similar asymmetry. We are the lopsided ape.