IELTS Academic Reading Practice Test 460

Christmas Island is a small Australian territory in the Indian Ocean, lying roughly 350 kilometres south of Java. About two-thirds of its surface is national park, and much of that is rainforest. The island is also home, by most estimates, to tens of millions of red crabs, a species found nowhere else in the world. For most of the year the crabs are almost invisible, living in burrows in the forest floor, feeding on fallen leaves and sheltering from the heat. Then, at the start of the wet season, they begin to move.

The signal for the migration is rain. The first heavy falls of the wet season, usually in October or November, soften the ground and raise the humidity, and the crabs emerge in enormous numbers. Their destination is the coast, and they travel with a determination that surprises visitors. An individual crab may walk several kilometres, and the journey can take a week or more, with the animals resting during the hottest part of the day and moving mainly in the early morning and evening. Dry spells halt the advance; so, increasingly, do roads.

Males generally set off first. On reaching the shore they dig burrows in the sand, sometimes in dense aggregations, and defend them against rivals with elaborate displays. A crab will rise high on its legs, spread its claws and, if the rival does not retreat, wrestle with it until one gives way. The burrow matters because it is where mating will take place and where the female will later incubate her eggs, so a well-placed one is worth fighting for. Females arrive a week or two after the males and mate in or near the entrance to the male's burrow.

After mating, the female remains underground for around twelve days. During this period she produces a brood of eggs, which are held in a sac beneath her abdomen. The number is remarkable: a large female may carry close to 100,000 eggs. Before releasing them she must return to the sea, and here too the timing is precise. The eggs are shed into the ocean on the highest tide around the last quarter of the moon, usually just before dawn, so that the receding water carries them out over the reef.

On the mornings when this happens, thousands of females descend the cliffs in the space of a few hours, and the shallows may darken with eggs. The crabs cannot swim and would drown in deep water, so they stay at the edge, raising themselves and stretching their bodies to shake the eggs loose. The release is over quickly. The females then climb back up the rocks, begin the long walk inland, and are followed some days later by the males.

The eggs hatch within a few days into larvae, which drift in the ocean for about a month and pass through several distinct stages as they grow. Their survival depends on conditions far beyond the island's control. A shortage of the tiny plants they feed on, a shift in the currents, or the arrival of predators can destroy an entire year's brood, and in some years almost no young crabs return at all. When the larvae have developed sufficiently, they come back to the shore as miniature crabs small enough to be hidden under a fallen leaf.

These young crabs emerge from the water in vast numbers over a few days, and for a short time the beaches and the edge of the forest appear to be moving. Most will not survive. They are eaten by birds, by lizards, by the island's large robber crabs and by adult red crabs, for which the returning juveniles are an important source of food. Those that reach the forest grow slowly and may live for more than twenty years, but they need moisture to breathe, and a hot, dry spell can kill them within hours.

The most serious threat of modern times has come from an invader. Yellow crazy ants, brought to the island by accident in the first half of the twentieth century, form sprawling supercolonies and attack crabs in groups, spraying them with formic acid and blinding them. Surveys in the early 2000s found that the ants had killed millions of crabs, and the forest in the worst-affected areas had fallen strangely silent. A long-running control programme has used aerial baiting and, more recently, a tiny parasitic wasp that attacks the scale insects whose sugary secretions feed the ant colonies; in some treated areas the crab population has begun to recover.

The migration also collides with the island's human geography. Roads cut across the routes to the sea, and early attempts to protect the crabs with fences simply stranded them beside the traffic. The island now closes several major roads during the migration and has built a network of bridges and tunnels that allow the animals to pass underneath. Signs warn drivers, and visitors are asked not to stop in the road to take photographs. Even so, thousands of crabs are killed by vehicles each year.

The migration has become the island's defining image and a considerable attraction for tourists, although its unpredictability frustrates the travel industry: the crabs' schedule is set by the weather, and a dry October can delay everything for weeks. For biologists, the event is a reminder of how closely a single species can be tied to the rain, the moon and the sea, and how easily those connections can be broken.

Suppose someone shows you a study that contradicts something you have believed for years. The reasonable response would be to weigh the new evidence and, if it is strong enough, change your mind. Anyone who has argued with a relative over the dinner table knows that this is rarely what happens. More often the conversation hardens both positions, and each person leaves with fresh arguments for what they already thought. Psychologists have spent several decades trying to explain this pattern, and their answers are more unsettling than the simple accusation that people are irrational.

The classic account of this stubbornness is cognitive dissonance. In the 1950s the social psychologist Leon Festinger and his colleagues studied a small group who believed the world would be destroyed on a particular date, and who had given away possessions in preparation. When the day passed and the world continued, the members did not abandon their belief. They adopted an explanation that allowed them to keep it and began to seek publicity for their views. Festinger argued that holding two incompatible ideas at once is uncomfortable, and that people reduce the discomfort by adjusting whichever idea is least costly to give up, which is often the new evidence rather than the cherished belief.

A closely related phenomenon is confirmation bias: the tendency to search for, notice and remember information that supports what we already think. In experiments, people read material on a contested issue and are far more likely to recall the arguments that favour their own side. They also judge supportive studies to be better designed than studies reaching the opposite conclusion, even when the methods described are identical. The bias operates at every stage, from the questions we ask to the way we interpret an ambiguous result.

Some researchers go further and argue that the strongest driver is not reasoning itself but belonging. On this view, beliefs about vaccination, diet or climate are markers of membership in a social group, and abandoning them means risking the disapproval of people whose good opinion matters. Experiments on risk perception have found that people with better numerical skills are not necessarily less divided on contested issues; if anything, they are more adept at interpreting inconvenient data in ways that protect their group's position. Being clever, in other words, does not make anyone immune. It may simply make the defence more sophisticated.

For a while, one finding seemed to capture the problem perfectly. In 2010 two American political scientists reported that correcting a false belief could produce a backlash: people who were shown a correction not only failed to change their minds but became more convinced of the original claim. The result became known as the backfire effect and was widely reported. Unfortunately, when other researchers tried to reproduce it with larger samples and different questions, they mostly failed. Backlash of this kind now appears to be real but rare, confined to particular issues and particular people, rather than the general rule it was once thought to be.

A better-supported phenomenon is the continued influence of misinformation. Once a claim has been accepted, it keeps shaping people's reasoning even after it has been retracted. Participants in such experiments readily acknowledge that a rumour was false, yet their answers still show that they have taken it into account. The usual explanation is a memory problem: the correction is absorbed, but the link between the claim and the correction is fragile, so the original information survives in the mind without its warning label attached. Corrections that merely deny a false claim can therefore leave the claim intact while adding a second, weaker memory beside it.

Repetition makes matters worse. In a well-established finding known as the illusory truth effect, statements that people have encountered before are rated as more likely to be true than statements they are seeing for the first time, even when they were told at the outset that the statements were false, and even when they cannot remember where they saw them. Familiarity is easily mistaken for evidence, and modern media supply familiarity in abundance.

None of this means that correction is futile. Research on how to correct effectively suggests several principles. The correction should repeat the fact rather than the myth, since repeating the myth strengthens it. It should explain why the false claim seemed plausible and offer a causal alternative. It is more likely to be accepted from a source the reader trusts, and it helps if the reader's sense of self is not under direct attack, which is why some interventions ask people to recall a time they acted on their own values before presenting unwelcome information.

There is also a social obstacle to changing one's mind. A person who reverses a long-held position may lose credibility with colleagues and feel foolish in front of family, and the cost of that loss can easily outweigh the benefit of being right. Any correction that ignores this is likely to fail, however well the evidence is presented.

What remains genuinely uncertain is how much all this matters outside the laboratory. Most studies use small, short-term measures with students or online volunteers, and few follow people for months to see whether a corrected belief stays corrected. The size of these effects in ordinary life, where beliefs are supported by friends, employers and years of habit, is largely unknown. It is also unclear whether the various remedies work equally well for everyone, or whether they depend on the issue and the audience.

Every few years a university department somewhere announces that its final examinations will be open-book, and every few years the announcement is greeted with the same complaint: that standards are being lowered. The image is familiar: students filing into a hall with trolleys of notes, then copying answers from a textbook. The reality, as anyone who has marked such an examination knows, is usually different and rather less comfortable for the students. Whether candidates should be allowed to consult material while they are being examined is worth taking seriously, because the answer goes to the heart of what an examination is for.

Open-book assessment is not a recent invention. Professional bodies in fields such as law and accountancy have long allowed candidates to consult statutes, tables or reference works, on the grounds that the skill being certified is the use of those materials, not the memorisation of them. Some medical examinations are open-book for similar reasons. What is newer is the extension of the practice into general undergraduate courses, where it is often introduced for reasons that have less to do with professional practice than with a belief that memorisation is no longer worth testing.

The case in favour rests on a claim about what examinations measure. In most subjects, supporters argue, the facts a student can recall under pressure are a poor indication of understanding: a candidate may remember a definition and still be unable to use it. Open-book papers allow examiners to set tasks that require the comparison of sources, the application of a principle to an unfamiliar case, or the evaluation of a claim, because students no longer need to spend their time reproducing material they could look up. There is also a humane argument. Anxiety harms performance, and some students who understand a subject perfectly well freeze when asked to recall a formula from memory.

Critics reply that this reasoning underestimates the value of secure knowledge. A student who must look up every definition never develops the fluency that comes from having facts at instant command, and fluency is what allows a person to notice that something is wrong, or to see a connection between two distant ideas. Some teachers also report a practical effect: when students know a book will be available, they prepare less thoroughly, and the examination becomes a test of navigation under time pressure rather than of understanding. Others add that open-book papers are harder to mark consistently, since answers vary more.

What does the evidence say? Reviews comparing the two formats have generally found that students do at least as well in open-book examinations, and on questions requiring application they often do better. But the comparison is harder than it looks. The two formats rarely pose identical questions, and an open-book paper that simply reuses closed-book questions will mostly measure how quickly a candidate can find a paragraph. Where examinations have been carefully redesigned, the differences in overall marks tend to be modest; where they have not, the results tell us little about the format itself.

This points to the central issue, which is design rather than permission. An open-book paper has to be written for the conditions in which it will be taken. Questions that ask for a definition invite students to copy; questions that supply an unfamiliar case and ask for a judgement cannot be answered by copying, because the answer is not in the book. Examiners who make the change often report that they must work harder than before, and that the marking criteria need to be rewritten to reward reasoning rather than the reproduction of correct content.

Fairness is more complicated than either side usually admits. Open-book conditions may help candidates whose anxiety interferes with recall, and those who think well but slowly. They may, however, favour students who own the recommended texts, who write efficient notes, or who have been taught how to use an index. A closed-book examination, by contrast, rewards the kind of sustained practice that a well-resourced school can provide. Neither format is neutral, and the claim that one is simply easier than the other obscures the fact that they reward different things.

What remains uncertain is how much any of this matters in the long run. There are few large studies that follow students beyond the examination, and almost none that compare what graduates can do several years later after being assessed in one format or the other. It is also unclear how far findings from one discipline transfer to another: an open-book examination in history, where the skill is the handling of sources, raises different questions from one in chemistry, where a misremembered constant can invalidate an entire calculation.

My own view is that the argument is misdirected. Asking whether open-book examinations are easier is like asking whether a bicycle is faster than a car without saying where you are going. The choice should be governed by what the qualification is meant to certify. Where the purpose is to establish that a student can reason with material, an open-book paper is the more honest instrument; where the purpose is to establish that essential knowledge is secure and available without hesitation, some closed-book assessment is indispensable. Most courses need both, and the real failure is not the presence of notes in the hall but the absence of any serious thought about why the examination is being held.