Practice Test 29: Sleep and the Making of Memories and the Return of Ancient Grains

A For centuries sleep was thought of as a passive state in which the mind simply switched off. Research over the last few decades has changed this view. During sleep the brain is highly active, and one of its main jobs appears to be memory consolidation, the process by which newly learned information is stabilised and stored for the long term.

B Sleep is not a single state. It moves through cycles that include deep, slow-wave sleep and rapid eye movement, or REM, sleep. Scientists suggest that slow-wave sleep is particularly important for facts and events, while REM sleep may help with skills and emotional memories. In one well-known type of experiment, students learned lists of word pairs and were then tested. Those who slept between learning and testing recalled more pairs than those who stayed awake for the same period.

C These findings have practical implications. Staying up all night to revise is often counterproductive, because the material studied late at night may not be consolidated and tiredness lowers concentration the next day. Short naps can help, and some studies have found benefits from naps of between twenty and ninety minutes. Researchers have also pointed out that teenagers' body clocks tend to shift later, so very early school start times may leave many students short of sleep.

D There are limits to what is known. Sleep cannot replace studying, because a memory has to be formed before it can be strengthened. Individuals also differ in how much sleep they need and in how well they recall what they have learned. For these reasons, researchers advise students to treat regular, sufficient sleep as part of their study routine, not as time taken away from it.

A Walk into a modern supermarket and you may find a shelf of grains with names such as millet, sorghum, spelt and quinoa. They are often sold as ancient grains, a term that has no strict scientific definition. It is usually applied to cereals and seeds that have changed little through selective breeding, in contrast with modern wheat and rice, which have been developed intensively for higher yields.

B One reason for their return is nutrition. Many of these grains contain more fibre and certain minerals than refined wheat flour, and some are free of gluten, which makes them useful for people who cannot eat it. A second reason is resilience. Millet and sorghum, for example, can grow in dry conditions and poor soils where other crops fail, and farmers in regions that are becoming hotter and drier see this as a valuable advantage.

C There are obstacles, however. Ancient grains usually give lower yields than modern varieties, which means they are more expensive to grow, and that cost is passed on to the consumer. Many countries also lack the machines and mills needed to process them on a large scale, and some shoppers are unfamiliar with how to cook them.

D Some nutrition experts warn that the label can be a marketing device, because the differences between these grains and other whole grains are often modest. Even so, many agricultural scientists welcome the trend, because growing a wider range of crops makes food supplies less dependent on a few species. In their view, the strongest case for ancient grains is not that they are healthier than everything else, but that they add diversity.