Multi-tasking and the brain

A Do you think you're a master of multi-tasking? Think again. Unless you are one of the three percent of super-taskers in the population, research shows that your brain is incapable of paying close attention to more than one complex task at a time. Researchers who study attention say that effective multi-tasking is beyond most of us. Psychiatrist Edward M Hallowell even describes multi-tasking as a 'mythical activity in which people believe they can perform two or more tasks simultaneously as effectively as they can perform one'.

B It’s true that you can check your email while eating your lunch, or listen to music while walking. But innate activities like walking, chewing, and breathing do not require you to pay attention, whereas activities such as reading, tapping out a text message or driving a car do require attention. Why is paying attention to two things at once difficult? 'The brain can perform simultaneous tasks, but attention has capacity limitations,' says Associate Professor Paul E Dux, a cognitive neuroscientist at the University of Queensland in Australia. When you do only one thing at a time, you’re better at that task than when you're doing multiple things concurrently.

C Take the classic multi-tasking scenario of talking on a mobile phone while driving – an ill-advised activity that many people believe they have mastered. When David Strayer, Professor of Psychology in the University of Utah in the US, and his team observed 56,000 drivers as they approached an intersection. The majority of drivers who were talking on their phone failed to stop in accordance with traffic laws. And it did not matter if the driver was using a handheld or hands-free device. Even with both eyes on the road and both hands on the wheel, drivers' performance was impaired. Strayer’s research shows that performance deteriorates dramatically when attention is split between tasks: more mistakes are made and it takes longer to complete each activity.

D The prefrontal cortex is the brain region responsible for choosing what to pay attention to, and for coordinating inputs from other brain areas. By scanning the prefrontal cortex of people while they multi-tasked, scientists at the French Institute of Health and Medical Research in Paris (INSERM) found that when people focused on a single thing, the right and left sides of the prefrontal cortex work together. But when people attempt to perform two things at once, the sides work independently. Neuroscientist Etienne Koechlin says his study demonstrates that while the brain can switch back and forth between two tasks, we might be in great trouble when we try to juggle more than two tasks simply because we have only two frontal lobes.

E To the question of whether there is a difference between the sexes, Koechlin's imaging studies uncovered no differences in the ability switch between tasks in the prefrontal cortices of men or women. But other researchers studying real life scenarios such as finding lost keys, believe there might be truth to the claim that women are superior multi-taskers. Women have a much better strategy for finding the keys, whereas men tend to jump to it and be far less organised and thorough. 'It's as if they don't stop to reflect and plan for a moment,' says Professor Keith Laws from the University of Hertfordshire in England. But while the ability to develop strategies for coping with the numerous tasks in everyday life could give women an advantage, 'nobody can juggle two, never mind three, “complex” tasks at the same time.'

F However, David Strayer's research uncovered that some rare people possess extraordinary multi-tasking ability. These so-called 'super-taskers' exhibit different patterns of brain activity when multi-tasking compared to ordinary people: they show less activity in the prefrontal cortex during multi-tasking suggesting their brains are functioning with a high level of efficiency. Strayer thinks that pilots of high-performance aircraft, high-end chefs who can cook several meals at the same time to perfection, and elite doctors in hospital emergency rooms might all be more likely to be super-taskers. 'All other things being equal, we suspect that super-taskers will rise to a top position in any occupation that places a high demand on juggling numerous tasks that demand attention at the same time.' The ability to multi-task probably comes down to the DNA you inherit from your parents. To a large extent, says Strayer. 'You are either born with the neural structure that allows you to overcome the usual multi-tasking challenges, or you aren't. Super-taskers' brains are doing something we can’t do.' All in all, these findings may have very real consequences on our lives.

Living dunes

A Armies of giant sand dunes are advancing across the world's deserts, engulfing anything that crosses their path. They are tens of metres tall and hundreds of metres long. Fortunately, they aren't going very fast. Even the smallest, speediest dunes only travel about 100 metres over the course of a year, while the bigger ones, which weigh something in the order of 10,000 tonnes, barely move one metre in that time. However, their insidious creep can have serious consequences if there is an oil installation or a railway line in their path.

B About 47% of the world's land mass, including Antarctica, most of Australia and large areas of Africa, is classified as arid or semi-arid desert. Only around 20% of that is sand-covered, however, and over half of that is classified as 'linear' sand dunes. These form in a long curving wave, as a result of wind blowing strongly from several quarters, flipping them from side to side. Although linear dunes are static, sand blowing off them can cause problems for desert villages, burying crops and buildings.

C Moving dunes make up just a small percentage of the rest, but they are of the most interest to scientists. They are known as 'barchans': heavy, crescent- shaped sand piles with a ridged crest and two elongated arms, one curving away to either side. 'Barchan dunes only tend to form where you have one- directional winds on the edge of sandy deserts near coastal areas,' says Giles Wiggs, a geomorphologist at Oxford University, who has been studying the formation and movement of sand dunes for more than a decade.

D But even with strong winds, how can entire barchans move while retaining their form? That question was first answered in the mid-20th century by British explorer Ralph Alger Bagnold, and his answer hinges on the fact that dunes aren't solid, but granular. Bagnold figured out how barchan dunes are able to move grain by grain. Imagine a single grain of sand being blown up the back of a dune by the wind and deposited on the top. More grains follow the same pattern, until the accumulated weight of piled-up sand finally pushes the top down the dune face. The grain tumbles, then stops on the face until subsequent mini- avalanches bury it. Eventually, it reappears at the back of the dune, ready to repeat the process. As this happens to every grain of sand in the dune, the whole thing creeps in the direction of the prevailing wind.

E The relationship between the wind and barchan dunes is complex. As a dune grows, it modifies the speed and course of the wind, which in turn alters how that dune and its neighbours evolve. 'Interestingly the dune can regulate its own shape, and maintain it as it moves,' says Dr Stephane Douady, a physicist at Ecole Normale Superieure (ENS) in France. 'Even when two dunes collide, they quickly take on their distinctive shapes again. It's like a living organism.'

F Douady and his colleagues have also been studying an even odder phenomenon than moving dunes: some barchans actually sing. Local legends attributed the sounds to dangerous spirits which were trying to trap unwary travellers. Douady is more pragmatic. 'It's a strong booming noise with a low frequency,' he explains, making a noise like a foghorn to demonstrate. 'It can last for a long time up to several minutes. It's a very loud sound and you don't understand where it's coming from when you first hear it.' There are about 50 dunes distributed across 35 deserts round the world that are known to sing. Douady says the sound is caused by the way sand avalanches down the faces of particular dunes. Rather than tumbling randomly, the sand grains flow in synchrony and set each other vibrating like the membrane on a gigantic loudspeaker. The synchronisation causes the air to move in and out between the grains, creating a powerful sound wave.

G What really surprised the scientists, however, was that they were able to take samples of the singing sand back to France and replicate the sound at ENS, proving that it's the sand, not the dune shape, that causes the sound. Their studies show the grains are a uniform shape, well-rounded from years of striking each other, and that the variations in size affect the tone. Crucially, the grains are coated with a special veneer, which Douady calls "desert glaze', made from a precise combination of minerals from surrounding rocks including iron aluminium, manganese, silicon and calcium. The team found that after a month or so, the veneer wore off and the grains lost their voice'. "We managed to reproduce the desert glaze and then the grains started to sing again,' says Douady. We tried putting the coating onto different grains, but they weren't round enough and it didn't work. But some American colleagues made some artificial grains and managed to make them sing, after covering them in desert glaze.' Douady has now made recordings of dunesong from all over the world which is to be made into a CD.