IELTS Academic Reading Practice Test 94

Animation is the process of creating the impression of movement by presenting a rapid series of slightly different still images. When these images are shown at a suitable speed, the human visual system fuses them into continuous action. For much of the twentieth century this effect was popularly attributed to 'persistence of vision', the idea that the retina briefly retains an image after it has gone. Modern researchers, however, regard that explanation as incomplete, because motion perception arises from several interacting brain processes rather than from a single retinal delay. In practice, a sequence of about twenty-four frames per second is generally enough to produce smooth movement.

The earliest moving-image devices were mechanical toys built in the nineteenth century. The phenakistoscope used a spinning disc with a sequence of drawings around its edge; when the disc was held in front of a mirror and spun, the figures appeared to move. The zoetrope placed a strip of drawings inside a slotted drum, so that a viewer looking through the moving slots saw each picture in turn.

Before either of these, the simple thaumatrope had shown that two images, one on each side of a card, could be made to merge by spinning the card rapidly. Later, the praxinoscope replaced the slots with an inner ring of mirrors, producing a brighter and steadier image. These devices all depended on the same principle that would later drive cinema and television: a quick succession of still pictures.

The photographic analysis of motion provided a further foundation. In the late 1870s, the English-born photographer Eadweard Muybridge settled a long-running debate by using a row of cameras to photograph a horse as it ran, showing that at certain moments all four hooves left the ground. The cameras were triggered automatically as the horse passed, and the resulting stop-action photographs were published and studied widely. Such sequences encouraged artists and inventors to think of movement as a series of separate phases that could be recorded and then reproduced.

By the early twentieth century, filmmakers had begun to make drawings move on screen. The American J. Stuart Blackton produced short films in which faces and objects drawn on a blackboard changed from frame to frame, while in France Émile Cohl's Fantasmagorie, released in 1908, is often described as the first fully animated film. Such films were painstaking to make: every second of action required many drawings, each photographed individually by a camera that stopped between exposures. The labour was immense, but these early works showed that moving drawings could tell stories and hold an audience.

As animation became an industry, studios developed techniques to make production manageable. A film was planned as a storyboard, after which key drawings defined the main poses of each movement. Assistants then produced inbetween drawings to connect these extremes, creating smooth action. To avoid redrawing static parts, characters were drawn on transparent celluloid sheets, or cels, which could be laid over painted backgrounds. This division of labour allowed teams of artists to produce longer and more elaborate films, though at considerable cost, and it remained the standard method for most hand-drawn animation for decades.

Character animation soon became the centre of the form. Winsor McCay astonished audiences in 1914 with Gertie the Dinosaur, a performing dinosaur that seemed to have its own personality. In the 1920s characters such as Felix the Cat, created independently of the major studios, became internationally popular. Walt Disney's studio then transformed the medium: Steamboat Willie (1928) was among the first cartoons to synchronise sound with movement, and Snow White and the Seven Dwarfs (1937) demonstrated that audiences would watch a feature-length animated film. The success of these films encouraged other studios to invest heavily in animation.

Drawn animation was not the only approach. In stop-motion, animators moved physical models a fraction at a time and photographed each position. This method was used for spectacular creatures in early fantasy films and was later refined by artists such as Ray Harryhausen, whose model dinosaurs and skeletons appeared in adventure movies. Other techniques included cutting shapes from paper, moving sand or paint on glass, and pinscreen animation, all of which offered distinctive textures and movements. Some animators also experimented with drawing directly onto film stock, producing abstract works.

Television created new economic pressures. Studios producing weekly cartoons could not afford the detailed full animation of cinema, so they adopted limited animation: characters' bodies were reused from a small library of poses, and only selected features moved. Hanna-Barbera, for example, built successful television series on this system. Japanese studios similarly developed a distinctive style in which strong storylines and dynamic camera angles compensated for fewer drawings, forming the basis of the anime tradition. These approaches showed that economic constraints could inspire artistic innovation.

The most far-reaching change came from computers. Early digital animation involved wire-frame models, but by the 1980s images generated or enhanced by computers were appearing in feature films. Toy Story, released in 1995, was the first feature made entirely with computer animation. Since then, most studios have shifted to digital methods, using software to model characters, simulate cloth and water, and even capture the movements of human actors. What began with spinning discs has become a central medium of popular culture, with animated features regularly among the highest-grossing films.

Smell is often treated as less important than sight or hearing, but it is a remarkable chemical detection system. Every time we breathe, airborne molecules called odorants enter the nose and provide information about food, danger and other people. Unlike vision or hearing, smell is linked directly to brain regions involved in emotion and memory, which helps explain why a particular scent can instantly recall a distant past experience. The sense also shapes the perception of food, since much of flavour is actually odour. Despite this, smell was neglected for much of the twentieth century, partly because it is hard to measure in the laboratory.

The detection of odours begins high in the nasal cavity, in a patch of tissue called the olfactory epithelium. Odorant molecules must first dissolve in the mucus that covers this tissue. They then bind to receptor proteins on the cilia of olfactory sensory neurons. Each neuron carries one type of receptor, and the human genome contains several hundred genes for these receptors, though only about four hundred are functional. When an odorant fits a receptor, the neuron sends an electrical signal along its axon to the olfactory bulb, a structure at the front of the brain. There, the signals are sorted and passed to higher regions.

Olfactory perception is a combinatorial code. Most natural smells are mixtures of many different molecules, and each molecule can activate several receptor types. The brain interprets the pattern of activity across the entire set of receptors, rather like reading a chord of notes rather than a single tone. This explains why humans can distinguish an enormous number of smells, even though the number of receptor types is limited, and why small changes in a mixture can make a scent smell completely different. A famous early study in the 1920s suggested that humans could detect roughly ten thousand smells, but later estimates have put the figure far higher.

From the olfactory bulb, signals travel directly to the piriform cortex and then to the amygdala and hippocampus, structures with central roles in emotion and memory. This direct route may explain the power of smell to bring back vivid autobiographical memories. In one well-known psychological phenomenon, odours evoke memories that feel more emotional and are judged older than memories triggered by words or pictures. The effect is often called the Proust phenomenon, after the novelist Marcel Proust's description of a madeleine cake dipped in tea. Because the olfactory system communicates so rapidly with these limbic structures, a smell can provoke a full emotional response before we have consciously identified it.

Sensitivity varies widely between individuals and across the lifespan. Some people are born with specific anosmias, meaning they cannot detect particular compounds, such as the musky substance androstenone. Genetic differences in receptor genes account for much of this variation. Recent research has also shown that the sense of smell can be improved with practice: wine tasters and perfumers are not simply born with exceptional noses but learn to categorise and name odours. With age, however, the number of receptor neurons declines and many older adults report a reduced ability to detect faint smells. Hormonal changes, head injuries and chronic nasal conditions can also affect sensitivity.

Smell is important not only when breathing in through the nose. When we chew food, volatile molecules travel from the mouth up into the nasal cavity through a passage at the back of the throat, a process known as retronasal olfaction. This is why food seems dull when the nose is blocked by a cold. Taste proper is limited to qualities such as sweet, salty, sour, bitter and umami, while the thousands of food nuances we speak of are mostly smell. Chefs and food scientists therefore talk about flavour as a whole-mouth experience in which the nose plays the larger role.

The sense also contributes to safety and social behaviour. The smell of smoke or spoiled food can act as a warning, and gas companies deliberately add a strong-smelling compound to otherwise odourless natural gas. In social contexts, human body odours appear to carry information about kinship and perhaps emotional state, although the existence of human pheromones remains controversial. Newborns and mothers also use smell in bonding, and a baby can recognise the scent of its mother within days of birth. Experiments have shown that mothers can identify their own baby's clothing by smell alone. Some researchers argue that individual body odour is as distinctive as a face.

Smell loss, or anosmia, is more than a minor inconvenience. It is associated with depression, reduced appetite and an impaired ability to detect hazards. In the early stages of several neurodegenerative diseases, including Parkinson's and Alzheimer's disease, a decline in smell can appear before other symptoms, making it a possible early warning sign. During the recent pandemic, many patients reported a sudden loss of smell, drawing public attention to the sense. The condition also prompted new research into the mechanisms of smell loss and recovery. Olfactory training, in which patients sniff a set of distinctive scents daily, has become a common treatment.

In the popular imagination, peer review is the gold standard of science, a filter that separates reliable knowledge from speculation. When a claim has been 'peer reviewed', journalists and public officials treat it as authoritative. Yet this confidence rests on surprisingly thin evidence. Peer review as it is practised today has never been subjected to rigorous testing, and many of its effects are now being questioned. In my view, peer review is necessary, but it is a human institution and therefore fallible; the question is not whether to keep it, but how to reform it. The phrase 'peer reviewed' is often used as if it meant 'proved', and that is precisely the error.

The origins of peer review lie in the seventeenth century, when learned societies began asking members to comment on papers before they were read or printed. The modern system emerged only after the Second World War, when the growth of scientific publishing and the arrival of public research funding made informal editorial judgment seem insufficient. By the 1970s and 1980s, anonymous review had become standard at most journals, and publication in a peer-reviewed journal had become the main measure of academic success. Commercial publishers also began to launch a large number of new journals.

The procedures are familiar. An editor receives a manuscript and sends it to usually two or three reviewers, who are active researchers in the field. These reviewers, who are almost always unpaid volunteers, write reports recommending acceptance, revision or rejection, and the editor uses their advice to decide. The system depends on goodwill, yet it operates in an environment in which reviewers receive little training, no financial reward and almost no public recognition. They must squeeze the work into evenings and weekends, alongside their own teaching and research.

Evidence about the reliability of this process is troubling. In controlled experiments in which researchers have inserted deliberate errors into manuscripts, many reviewers fail to spot even major mistakes. Reviews of submitted manuscripts often disagree in their recommendations, and two readers of the same paper can reach opposite conclusions. Peer review is not designed to detect fraud: reviewers see only the completed manuscript, not the laboratory notebooks or raw data, so a determined forger who writes convincingly may pass through. The widely cited retraction of a paper linking a common childhood vaccine to autism, which was later found to be fraudulent, demonstrated the limits of the process. A reviewer cannot be expected to repeat experiments, and most spend only a few hours on a manuscript.

Bias is another concern. Reviewers are more likely to favour papers from prestigious institutions, well-known authors and English-speaking countries. Studies of anonymised submissions have found that identical work is rated more highly when the name of a famous researcher is attached. Reviewers may also be unconsciously hostile to ideas that challenge their own work. Peer review tends to be conservative, favouring incremental research over genuinely novel claims. This does not make dishonest reviewers; it makes human ones.

The publication process also distorts the scientific record. Editors prefer to publish positive results, and researchers respond by selecting and analysing data in ways that produce positive findings, a set of practices often summarised as 'p-hacking'. Negative or inconclusive studies seldom reach print, creating publication bias, in which the published literature represents only a partial and flattering view of what has been found. The pressure to publish also fuels the growth of so-called predatory journals, which claim to carry out peer review but actually charge large fees and publish almost anything.

Several reforms are being discussed. Open peer review, in which reviewers sign their reports, is designed to encourage civility and accountability, although critics worry that junior researchers may be reluctant to criticise senior figures. Post-publication review uses the internet to allow any reader to comment, correct or question a paper after it has appeared. Preprint servers make manuscripts available before formal review, speeding up the exchange of ideas while placing responsibility on readers to judge quality. Registered reports, in which a journal accepts a study's methods and analysis plan before results are known, tackle publication bias by promising publication even if the findings are not exciting.

These experiments point in the right direction, but none is a complete solution. A preprint, for example, reaches the public without the filter that peer review is supposed to provide, and open review can simply replace one set of biases with another. More important, in my view, are changes to the incentives and infrastructure of science. Journals should require authors to share raw data wherever possible, and reviewers should receive credit for their work, perhaps through platforms that list their reports. Training in how to review should become part of doctoral education, and universities should reward reviewing in promotion decisions. The goal should be to make the published record more transparent and reproducible, rather than merely more polite.

Peer review will not disappear, nor should it. Science needs structured critical evaluation by knowledgeable colleagues, and no algorithmic tool can yet replace human judgement. But the present system, despite its achievements, is too slow, too unreliable and too easily manipulated to serve as the sole guarantee of scientific truth. The public should stop treating the two words 'peer reviewed' as a certificate of certainty. Reform, not ritual, is what the scientific record requires.