IELTSwithJurabek

You should spend about 20 minutes on Questions 14-26, which are based on Reading Passage 2 on pages 6 and 7.

How sleep helps us learn

Researchers are uncovering the link between sleep and learning and how it changes throughout our lives.

A Most research into the relationship between memory and sleep has traditionally been conducted using young adults or animals. By the early 2000s, scientists had found that sleep helps young adults consolidate memory by reinforcing and filing away daytime experiences, but the older adults that Rebecca Spencer was studying at the US University of Massachusetts Amherst didn't seem to experience the same benefit. Spencer wondered if age altered the relationship between sleep and memory, and chose nearby preschool children as subjects. She found that the children who regularly had short sleeps during the day benefited the most from daytime rest, largely because their memories decayed the most without these naps. By staying awake, they have more interference from daytime experiences, Spencer explains.

B The studies on young adults carried out in the early 2000s suggested that the reduced sensory inputs during sleep allow the brain to replay daytime experiences during a period relatively free of distracting information. This may help to solidify connections and transfer daytime memories from the hippocampus into long-term storage in the cortex. But how sleep and memory interact at different periods of our lives remained an open question.

C In children younger than 18 months, learning is thought to occur in the cortex because the hippocampus isn't yet fully developed. As a result, researchers hypothesize that infants don't replay memories during sleep the way adults do. Instead, sleep merely seems to prevent infants from forgetting as much as they would if they were awake. The net effect is that sleep permits infants to retain more of the redundant details of a learning experience, says experimental psychologist Rebecca Gomez of the University of Arizona. By the time they are two years old, 'we think that children have the brain development that supports an active process of consolidation', she adds.

D From the age of two, adequate sleep during the hours of darkness becomes critical for learning. Toddlers who sleep less than 10 hours display lasting cognitive deficits, even if they catch up on sleep later in their development. The effects are particularly strong in children with developmental disorders, who often suffer from disturbed sleep. Jamie Edgin of the University of Arizona studied children with the genetic disorder Down syndrome, comparing those who were sleep-impaired with those who slept normally. She found that there were large differences in language knowledge and observed that the non-sleep-impaired children knew up to 190 more words, even after controlling for behavioural differences.

E Understanding the impact of sleep on memory could also help another at-risk group of learners at the other end of the age spectrum. Previous research has suggested that older adults don't remember recently acquired motor skills as well as young adults do. But neuroscientist Maria Korman and her colleagues at the University of Haifa in Israel recently demonstrated that taking a nap soon after learning can allow the elderly to retain procedural memories just as well as younger people. Korman hypothesises that by shortening the interval between learning and consolidation, the nap prevents intervening experiences from weakening the memory before it solidifies. Overnight sleep might be even better, if the motor skills - in this case a complex sequence of finger and thumb movements on the non-dominant hand - are taught late enough in the day.

F Optimising the timing of sleep and training in the elderly exploits something Korman sees as a positive side of growing old. 'As we age, our neural system becomes more aware of the relevance of the task,' Korman says. Unlike young adults, who solidify all the information they acquire throughout the day, older people consolidate those experiences that were tagged by the brain as very important.

G Tests on older adults' memories are generating new findings about the relationship between sleep and memory at other ages as well. After learning at a conference about a memory test for cognitive impairment and dementia in older adults, neuroscientist Jeanne Duffy of Brigham and Women's Hospital in Boston wondered if sleep could help strengthen the connection between names and faces. She and her colleagues found that young adults who slept overnight after learning a list of 20 names and faces showed a 12 percent increase in retention when tested 12 hours later, compared with subjects who didn't sleep between training and testing. The findings have 'an immediate real-world application', Duffy says, as they address a common memory concern among people of all ages.

H Developing a fuller picture of what happens to memories during sleep - and how best to modify sleep habits to aid the recall process - could benefit some of society's most sleep-deprived members of every age. 'We need to understand this role of sleep in memory because there is such potential for intervention,' Spencer says. 'Now that we have a well-founded concept of what sleep can do for memory, it's time to put it to the test.'

You should spend about 20 minutes on Questions 27-40, which are based on Reading Passage 3 on pages 10 and 11.

Petrol power: an eco-revolution?

Laura Ingalls Wilder's semi-autobiographical novel The Long Winter describes how the inhabitants of a small town called De Smet in the American mid-west narrowly avoided starvation during the severe winter of 1880-1881. Over three metres of snow fell on the northern plains, immobilising the railways and cutting off the settlers from the rest of the world. Laura and her neighbours were only saved when her fiance and his friend trudged 30 kilometres through the snow to fetch food, risking their lives in the process. The story is a reminder of how lethal geographical isolation and crop failures could be before the advent of modern farming and transportation technologies. Not long ago, subsistence farmers in many countries had to cope with the 'lean season' - the period of greatest scarcity before new crops became available. In England, late spring was once referred to as the 'hungry gap'. The situation was made worse by the cost of moving heavy things over muddy dirt roads; three centuries ago, moving goods 50 kilometres on land between, say, Liverpool and Manchester was as expensive as shipping them across the north Atlantic.

The development of coal-powered railways and steamships in the 19th century revolutionized the lives of farmers. Instead of having to grow everything they needed, they could now specialise in what they did best and rely on other producers for their remaining needs. The result was not only food and ever-cheaper prices, but the end of widespread famine and starvation, as the surplus from regions with good harvests could now be transported to those that had experienced mediocre ones. Since then, petroleum-derived fuels have largely displaced coal because of their higher energy density, cleaner combustion and greater ease of extraction, further improving road and rail transportation systems.

While the convenience of modern methods of transportation is obvious, few people grasp their historical significance in terms of their beneficial impact on large cities and the health of residents. In 1898, delegates gathered in New York City for the world's first international urban-planning conference: The topic that dominated discussions was not infrastructure or housing, but horse manure. The problem was that as the populations of cities like New York and London grew, the number of horses there also grew, and in New York these produced nearly two million kilograms of manure each day. If this problem continued it was estimated that by 1950 every street in London would be buried three metres deep in horse manure. Unable to think of any solution, the delegates concluded that urban living was inherently unsustainable.

Paradoxically, much of the urban manure problem was related to the growth of the railways. The ability to deliver perishable goods, such as meat and dairy products, from locations that benefited from better soil and climate, put many farms located near cities out of business. As these had relied on manure from city workhorses for fertiliser, the demand for this was greatly reduced.

The impact of urban workhorses was felt both in the cities and in the countryside. In cities, apart from their overpowering stench, the manure piles were prime breeding grounds for house flies, perhaps three billion of which hatched each day in US cities in the early 20th century. With flies came outbreaks of typhoid, cholera and diphtheria. Workhorses sometimes panicked in heavy traffic and kicked or bit bystanders. The clatter of wagon wheels on cobblestone pavement could be deafening, and since a horse and wagon occupied more street space than a modern truck, they also created significant traffic congestion, while a horse that collapsed on the road created an obstruction that was difficult to remove. The countryside also suffered. To supply the workhorses with oats and hay, additional land had to be cleared of its natural animal life and vegetation, and sometimes water had to be diverted to irrigate it, with considerable negative effects on the whole area.

So, while the trains, cars and trucks of the early 20th century were noisy and polluting by today's standards, they were regarded as a significant improvement on what had gone before. Before they were available, poor soils often meant that a large amount of land was required to sustain a household, and much environmental damage, primarily in the form of soil erosion, was caused by trying to farm these soils. It could be argued that modern transportation allowed the development of remote regions like the Canadian prairies and allowed more suitable crops to be grown in the poorer soils in Europe before being sold elsewhere.

Over time, the concentration of food production in the world's best locations allowed some agricultural land to revert to a wild state. For instance, France benefited from an expansion of its forest area by one third between 1830 and 1960. This so-called 'forest transition' occurred in the context of a doubling of the French population and a dramatic increase in standards of living. Improvements in logistics also allowed the production and export of food from locations where water was abundant to regions where it was scarce, thus preventing the depletion of water resources there. It also made possible a drastic increase in the size of our cities. Contrary to what most people believe, the growth in cities is a positive development. In the words of economist Ed Glaser: 'Residing in a forest might seem to be a good way of showing one's love of nature, but living in a concrete jungle is actually far more ecologically friendly... If you love nature, stay away from it.' It could be argued that modern transportation technologies have been a major contributor to a wealthier, cleaner and more sustainable world.