IELTS Academic Reading Practice Test 175

For much of the nineteenth century, anyone who wished to travel faster than walking pace depended on a horse or a bicycle. The motorcycle emerged where a strengthened bicycle frame met the small internal-combustion engine. The earliest machines were built in Germany, France, Britain and the United States within a few years of one another, and none would be recognised as a motorcycle today. Their makers were engineers testing an engine rather than entrepreneurs creating a new kind of transport.

Steam came first. Sylvester Roper, a sewing-machine maker in Massachusetts, attached a small steam engine and a vertical boiler to a strengthened bicycle frame in the 1860s. The machine is said to have run, but it attracted little interest, for there was no obvious use for it and no firm capable of building it in quantity. Roper died in 1896 after an accident on one of his vehicles. In Britain, Edward Butler showed a three-wheeled vehicle driven by a petrol engine in 1884, but it too remained a curiosity.

The machine most often described as the first true motorcycle was built in 1885 at Cannstatt, near Stuttgart, by Gottlieb Daimler with his assistant Wilhelm Maybach. Its single-cylinder four-stroke engine displaced 264 cubic centimetres, small and light enough for a bicycle-style frame. The frame was wooden, and two small outrigger wheels were fixed on either side, since the balance of a two-wheeled vehicle at low speed had not been solved. A belt carried power to the rear wheel. In November 1885 Daimler's son Paul rode the machine for a few kilometres beside the river. Daimler never offered it for sale; it was a test bed for an engine that later powered boats and cars.

Commercial production began a decade later. In 1894 a Munich firm, Hildebrand & Wolfmüller, announced a motorcycle with a water-cooled twin-cylinder engine, and it was the first such machine to be built in series rather than one at a time. Perhaps two thousand were made, but production stopped in 1897; the machine was heavy and its ignition unreliable. More important to the growth of the industry was the French firm De Dion-Bouton, which from the mid-1890s sold compact, dependable engines to other manufacturers, many of them bicycle makers looking for a new market.

Several of the names that would dominate the industry were established in the first decade of the twentieth century. Royal Enfield in Britain produced its first motorcycle in 1901, and Indian in the United States did the same; Harley-Davidson was founded in Milwaukee in 1903 by William Harley, then twenty-one, and Arthur Davidson. Motor sport drove development: the first Isle of Man TT was held in 1907 on public roads on the island, and the demands of the course exposed and rewarded improvements in tyres, brakes and engines.

Early motorcycles were direct-drive: the engine turned the rear wheel through a belt, with no clutch and no gears, and the rider started the engine, ran alongside and then climbed aboard. Clutches and two- and three-speed gearboxes spread during the first two decades of the twentieth century, and chain drive gradually replaced the belt. These changes, unglamorous in themselves, made the motorcycle usable in traffic. The First World War also demonstrated its value, since armies on both sides used motorcycles to carry messages, work for which a horse was too slow and a lorry too conspicuous.

Comfort and safety improved more slowly. Frames remained rigid for decades, so the rider's only springs were in the saddle and the tyres. Telescopic front forks with hydraulic damping appeared in the 1930s, and rear suspension followed; drum brakes grew more effective, and better tyre compounds raised the speeds that machines could reach safely.

After the Second World War the balance of the industry shifted to Japan. Soichiro Honda's company, founded in 1948, concentrated on small machines, and its Super Cub of 1958 was designed for delivery riders: a small four-stroke engine, a step-through frame and an automatic clutch that let the rider change gear without a clutch lever. It became the most widely produced motor vehicle in history, with more than a hundred million built. Honda, Yamaha, Suzuki and Kawasaki came to dominate world markets, and Honda's four-cylinder CB750 of 1969, which had a front disc brake, set the pattern for the powerful machines of the following decades.

Electronics have since changed what a motorcycle does as well as how fast it goes. BMW offered an anti-lock braking system on a production motorcycle in 1988, and the same firm later added traction control, which cuts engine power when the rear wheel begins to spin. Throttle cables have given way to electronic controls, allowing several riding modes on one machine, and sensors now measure lean angle so that braking can be adjusted in mid-corner. Electric motorcycles and scooters, meanwhile, have found a market in cities, where their silence and lack of exhaust emissions count for more than range.

Yet the motorcycle's importance is greatest where incomes are lowest. In much of Asia, small motorcycles and scooters carry commuters, passengers and goods in numbers that European and American statistics barely register, and they are often the cheapest way for a family to reach work, school and market. Their drawbacks — pollution from older two-stroke engines, injuries in crashes, noise — are serious, and several cities have tried to restrict them. But the machine that began as an engineer's experiment has proved remarkably hard to replace.

A smart textile is a fabric that does something beyond covering the body. Some sense a heartbeat or a movement; some change colour or release heat; a few are designed to deliver medicine through the skin. Most of the technology falls into one of two families. In the first, the electrical function is built into the yarn itself, so that the cloth behaves like a circuit woven from thread. In the second, an ordinary fabric is treated afterwards: it may be coated with a conductive ink, printed with carbon paste or embroidered with metallic thread. The first approach produces cloth that feels and washes like ordinary clothing; the second is cheaper and easier to adapt.

Metal is the most obvious material for a conductive thread, but a solid wire is stiff, heavy and quick to break when it is bent repeatedly. Manufacturers therefore coat fine filaments of nylon or polyester with a thin layer of silver, or they spin carbon into the yarn. Silver is popular because it conducts extremely well and, unlike copper, keeps working as an oxide layer forms on its surface. Carbon is cheaper and more hard-wearing, though it conducts less well. The resulting yarn can be handled by ordinary knitting and weaving machines, which is why conductive fabric is no longer expensive. Its weakness lies where the cloth is rubbed or stretched: the coating slowly cracks and flakes away, and the electrical resistance of the fabric creeps upwards.

Conducting electricity is useful only if the fabric can also sense something. The simplest smart textiles act as electrodes. The heart produces a voltage of about a millivolt at the skin, and a fabric containing conductive fibres, pressed against the chest, can record an electrocardiogram — a trace of the electrical signal that makes the heart beat. Such dry electrodes work best when the wearer is sweating slightly, because moisture carries the signal between skin and fabric. This is one reason why textile sensors are common in sportswear, where the wearer is likely to perspire.

Movement can be detected without any electronics attached to the cloth. Certain polymers, notably polyvinylidene fluoride, are piezoelectric: when they are stretched or compressed they produce a small charge. A knee sleeve knitted from such fibres gives out a pulse every time the wearer takes a step, and the same effect can record the rise and fall of the chest during breathing. A different technique measures capacitance, the ability of two conductive layers separated by an insulator to hold charge. When a finger approaches, the stored charge changes, and a small processor can register the touch.

Power is the constraint that shapes every design. A shirt can carry sensors and a radio, but it cannot easily carry a battery large enough to run them for long, and a heavy battery defeats the purpose of clothing. Designers therefore reduce consumption, using circuits that sleep between measurements and transmit only summaries. They also harvest energy locally. A thermoelectric element turns the difference between skin temperature and the air into a small current; piezoelectric fibres convert the flexing of an elbow or the impact of a heel into charge; and a patch of solar fabric can top up a battery in daylight.

Colour is the simplest visible response. Thermochromic pigments, which change colour as they warm, are enclosed in tiny capsules and printed onto fabric, so that a jacket can show the temperature of the wearer or simply alter its shade in the sun. Phase-change materials work less visibly. Microcapsules of wax are incorporated into the cloth; they melt as the body warms, absorbing heat, and solidify as it cools, releasing it again. The effect is modest, and it lasts only as long as the capsules survive repeated washing.

Fabrics can also act on the body rather than merely measure it. Shape-memory alloy wires, which return to a remembered shape when heated, can be woven in to make a sleeve that tightens or a panel that opens, and channels moulded into a textile can be inflated to apply pressure. Researchers in soft robotics use such materials to build gloves that help a patient who has had a stroke to close the hand, and the same principle underlies compression garments designed to massage a limb. The forces involved are small, and supplying power remains the chief difficulty.

Manufacture is harder than it looks. A rigid component attached to a garment creates a point where the cloth pulls, and that is usually where a device fails, so designers maximise what can be printed, knitted or embroidered and minimise what must be glued on. Washing is the standard test: detergents, heat and mechanical tumbling attack both coatings and capsules, and a textile that survives fifty cycles is considered good. Encasing the electronics in flexible polymer films helps, as does keeping connectors away from areas that stretch.

Where are such fabrics used now? Sports brands sell shirts that measure heart rate without a chest strap; hospitals are testing garments that monitor a patient's breathing and movement at home; and outdoor clothing includes jackets with built-in heating. The most ambitious promises concern medicine, where a fabric recording a signal continuously for weeks could replace equipment worn for a single day. Two obstacles remain. Regulation is one, since a garment that diagnoses must be approved as a medical device. The other is recycling, because cloth that mixes polyester, silver and electronic components is difficult to separate into usable materials.

Open the app store and you will find dozens of programmes promising to sharpen the mind. A few minutes a day, they suggest, will improve memory, attention and problem-solving, and may even delay the decline that comes with age. The market is large and the advertising confident. My own view, after reading a good deal of the research, is that these products do train something, but that what they train is narrower than their customers are led to believe, and that the gap between the evidence and the marketing is wider here than in almost any other area of consumer health.

The legitimate foundation of the industry is neuroplasticity, the capacity of the brain to reorganise itself in response to experience. This is not in doubt. Imaging studies of London taxi drivers have found that those with the longest careers have a larger posterior hippocampus, the structure associated with spatial memory, and a much-cited experiment in which young adults learned to juggle reported measurable increases in grey matter after three months of practice. The adult brain, in other words, is not a fixed machine. What such studies do not show is that a brief daily game produces general improvements, and that is the claim on which the industry depends.

Psychologists draw a distinction that the advertising usually ignores. Near transfer means getting better at the task you have practised, or at one very like it. Far transfer means improving at something else entirely — remembering where you left the keys, following a conversation in a noisy room, planning a shopping trip. Training studies reliably produce near transfer: people who practise a memory game become better at that memory game. Far transfer is the prize, and it is rarely found. A review of working-memory training published in 2013 concluded that the gains were real but confined to tasks similar to those trained, and a later, broader assessment reached much the same conclusion.

Matters came to a head in October 2014, when about seventy cognitive scientists signed a public statement warning that claims made by brain-training companies were exaggerated and misleading. Two years later the American Federal Trade Commission reached a settlement with Lumos Labs, the maker of Lumosity, which paid two million dollars and agreed to stop implying that its games would stave off cognitive decline or dementia. The commission's complaint described advertising that presented weak and sometimes industry-funded research as though it were settled. Such episodes explain why many researchers now approach the field with suspicion.

Yet it would be wrong to conclude that cognitive training does nothing. The best evidence comes from a large American randomised trial known as ACTIVE, which from the late 1990s followed more than 2,800 volunteers aged sixty-five and over for a decade. Participants were assigned to training in memory, reasoning or speed of processing, or to a control group. Ten years later, the groups trained in reasoning and in speed of processing still performed better on the abilities they had practised, although the differences were modest. The speed-training group also had fewer at-fault car crashes. BrainHQ, one of the commercial products, is built on that speed-of-processing method, and its claims are better supported than most.

The methodological objections are serious, however. Many trials compare a training game with doing nothing at all, so any improvement may reflect the attention that volunteers receive rather than the game. The better studies use an active control — a different game, or a task that looks similar but is designed to train nothing in particular — and these tend to produce smaller effects. Samples are often small, and the outcome most frequently reported is performance on the trained task itself, which makes the reasoning close to circular. Publication bias compounds the problem: trials that find nothing are less likely to appear in print, and some of the most enthusiastic results have been funded by the companies that sell the products.

What, then, should someone worried about their memory do? The evidence for physical exercise is stronger than the evidence for any game. Several large studies have linked regular aerobic activity with a slower decline in thinking skills, and the effect appears to be modest but genuine. Sleep matters too, as does treating poor hearing, which otherwise cuts people off from conversation. Social contact and the learning of genuinely new skills — a language, an instrument, a craft — have support that is at least as good as that for commercial brain training, and they are more enjoyable. The general principle seems to be that the brain benefits from doing something difficult and unfamiliar, not from repeating a task at which it has already become expert. None of these activities can be sold in an app store, which may be part of the problem.

None of this means that brain-training apps are worthless. They are cheap, they are pleasant to use, and they do what they say on the tin if the tin is read carefully: they make you better at the task in front of you. What they do not do is provide a shortcut to a sharper mind. Anyone choosing between a subscription and a brisk walk, a conversation or a first attempt at the piano should recognise that the evidence points away from the screen. The companies, for their part, should be required to show that their games improve something beyond the games themselves.