IELTS Reading Practice Test 10: Free, with Answers

AIn a converted warehouse on the edge of a city, rows of lettuces grow in trays stacked ten layers high beneath the pink glow of artificial lights. There is no soil and no sunlight. The plants' roots hang in water or are sprayed with a fine mist containing every nutrient they need, while the temperature, humidity and even the carbon dioxide content of the air are controlled by computer. Supporters of this kind of agriculture, known as vertical farming, claim that it could transform the way in which cities are fed. Critics regard it as an extremely expensive way of growing salad.

BThe term itself is older than the technology. It was first used in 1915 by the American geologist Gilbert Ellis Bailey, in a book of the same name, although he was writing about something quite different: ways of reaching the deeper layers of soil, which included the use of explosives. The modern idea is usually traced to Dickson Despommier, a professor at Columbia University in New York. In 1999, he challenged his students to work out how much food could be grown on the rooftops of Manhattan. When they calculated that rooftop gardens could feed only a small fraction of the population, Despommier suggested growing crops inside multistorey buildings instead, and his later book helped to turn the concept into a business.

CThe advantages claimed for vertical farms are considerable. Because crops are grown indoors, they are protected from droughts, floods and pests, so harvests are reliable throughout the year and chemical pesticides are rarely needed. Water is recycled through the system, and some companies say that they use up to 95 per cent less than conventional farms. Since the farms can be built close to where people live, produce can reach shops within hours of being picked, reducing both transport and waste. And because the plants are stacked in layers, a single building can produce far more food from each square metre of land than a field. Some producers also argue that their crops taste better, because they are harvested when fully ripe rather than picked early to survive long journeys, although such claims are difficult to verify.

DThe main reason vertical farming became practical in the twenty-first century was the falling cost of LED lighting. Earlier artificial lights produced a great deal of heat and wasted much of their energy, but LEDs are far more efficient and can be designed to emit mainly the red and blue light that plants use most in photosynthesis, which is why many indoor farms are bathed in a pinkish glow. Even so, replacing the Sun is expensive. Electricity for lighting and for controlling the temperature is typically the largest single cost of running a vertical farm, and in regions where electricity is generated by burning fossil fuels, the environmental benefits of such farms may be smaller than they first appear.

EThe cost of lighting also explains why vertical farms grow such a narrow range of crops. Leafy vegetables and herbs such as lettuce, spinach and basil grow quickly, are almost entirely edible and sell at high prices, so the expense of lighting them can be recovered. Staple crops are another matter. In 2020, a team of researchers calculated that wheat grown in a ten-layer indoor facility could produce between 220 and 600 times as much grain from each hectare of land as the world's average field. The grain would be so expensive to produce, however, that it could not compete with wheat grown outdoors unless energy became far cheaper.

FThe industry's finances have also proved fragile. During the 2010s, investors poured money into vertical farming companies, some of which built enormous facilities. When energy prices rose sharply in 2022 and interest rates increased, several of the best-known firms ran into difficulty. AeroFarms, an American company that had been among the most prominent in the sector, filed for bankruptcy protection in June 2023, and others closed altogether or withdrew from some of the countries in which they operated. A number of analysts concluded that the industry had expanded too quickly, building very large farms before the economics had been proven, and that optimistic forecasts had rarely accounted for the full cost of buildings, equipment and specialist staff.

GFew experts now believe that vertical farms will replace conventional agriculture, but many see a role for them. In places with little farmland or a harsh climate, such as Singapore and the countries of the Persian Gulf, growing vegetables indoors can reduce dependence on imports. Singapore, which imports the great majority of its food, has actively encouraged indoor farming as part of a wider effort to produce more of what it eats. Some farms are being combined with renewable energy, or built beside power stations and factories so that they can make use of heat that would otherwise be wasted. The most likely future, in other words, is not a city fed entirely from towers, but one in which vertical farms supply a modest share of the fresh food that is most difficult to transport.

Economists have traditionally taken a simple view of human behaviour: if you want people to do more of something, pay them, and if you want them to do less of it, make it more expensive. This principle explains a great deal, from the way shoppers respond to discounts to the way employees respond to bonuses. Over the past few decades, however, a series of studies has revealed situations in which offering money produces the opposite of the intended result. Understanding when and why this happens matters, because governments, schools and employers increasingly rely on financial rewards and penalties to influence behaviour.

The best-known example comes from a group of day-care centres in Haifa, Israel. Parents who arrived late to collect their children obliged teachers to stay after closing time, so the economists Uri Gneezy and Aldo Rustichini arranged for some of the centres to introduce a small fine for parents who were more than ten minutes late. The result surprised almost everyone: the number of late arrivals rose significantly. Before the fine, parents had presumably felt some guilt about inconveniencing the teachers; once a price had been attached to lateness, many seem to have regarded extra childcare as a service they could simply pay for. Most remarkably, when the fine was withdrawn some weeks later, lateness remained at its new, higher level. Once a moral obligation has been turned into a transaction, it seems, it can be difficult to turn it back.

Psychologists and economists describe this phenomenon as crowding out: an external reward displaces the internal motives, such as duty, generosity or pride, that previously drove a particular behaviour. The idea was anticipated as early as 1970 by the British social scientist Richard Titmuss, who argued that paying blood donors would reduce both the quantity and the quality of the blood supplied. His claim was controversial at the time, but a Swedish experiment published in 2008 offered some support for it. When women who had expressed interest in giving blood were offered a small payment, the proportion who actually donated fell from 52 per cent to 30 per cent. Yet when they were given the option of passing the payment to a children's charity, donations returned to their original level, suggesting that it was personal financial gain, rather than money as such, that discouraged them. Men, interestingly, were unaffected.

Similar effects have been observed in very different settings. In the 1990s, residents of Swiss communities that were being considered as sites for a nuclear waste store were asked whether they would accept it, and around half said that they would. When the same question was asked with an offer of generous financial compensation, support fell to about a quarter, apparently because people who had been prepared to accept a burden out of civic duty felt that they were being bribed. Even young children appear to be affected. In a classic study published in 1973, nursery school children who enjoyed drawing were promised a certificate for producing pictures. Later, once the rewards had ended, these children chose to spend less of their free time drawing than children who had received no reward, as if an activity they had once enjoyed for its own sake had become a kind of work.

None of this means that financial incentives never work. They are often highly effective when a task is dull and offers little satisfaction in itself, or when the people involved are poor enough for a modest payment to make a real difference to their lives. Mexico's Progresa programme, launched in 1997, made regular payments to mothers in poor families on condition that their children attended school and that family members visited health clinics, and careful evaluations found that school enrolment rose. Its success led to similar programmes in many other countries, although later studies suggest that their effects depend heavily on local circumstances, including the quality of the schools and clinics that families are being encouraged to use. The lesson of this research, then, is not that money corrupts every good intention, but that it interacts with motives that economists long ignored.

In my view, three principles follow. First, before introducing a reward or a penalty, policymakers should ask what already motivates the people concerned; where behaviour rests on duty or generosity, money may do more harm than good. Second, small payments are often the worst of both worlds, since they can destroy an existing sense of obligation without being large enough to provide a strong financial motive. Gneezy and Rustichini demonstrated this in a separate experiment, in which students collecting donations for charity raised less money when they were offered a small commission than when they were offered nothing at all. Third, rewards that recognise people, such as public thanks or the opportunity to help others, tend to reinforce rather than replace their own motives, as the Swedish women who could pass their payment to charity illustrate.

Economists were right to insist that incentives matter, but wrong to assume that money is the only incentive that does. People are moved by what others think of them, by what they think of themselves and by their sense of what is fair, and a payment can alter all three. The challenge for anyone designing a system of rewards is to work with these motives rather than against them.