第二篇

When Our Eyes Serve Our Stomach

All we have a clock located inside our brains. Similar to your bedside alarm clock, your internal clock2 runs on a 24-hour cycle. This cycle, called a circadian rhythm, helps control when you wake, when you eat and when you sleep.

Somewhere around puberty, something happens in the timing of the biological clock. The clock pushes forward, so adolescents and teenagers are unable to fall asleep as early as they used to. When your mother tells you it's time for bed, your body may be pushing you to stay up3 for several hours more. And the light coming from your computer screen or TV could be pushing you to stay up even later.

This shift4 is natural for teenagers. But staying up very late and sleeping late can get your body's clock out of sync with the cycle of light and dark5. It can also make it hard to get out of bed in the morning and may bring other problems, too. Teenagers are put in a kind of a gray cloud6when they don't get enough sleep, says Mary Carskadon, a sleep researcher at Brown University in Providence, RI7. It affects their mood and their ability to think and learn.

But just like your alarm clock, your internal clock can be reset. In fact, it automatically resets itself every day. How? By using the light it gets through your eyes.

Scientists have known for a long time that the light of day and the dark of night play important roles in setting our internal clocks. For years, researchers thought that the signals that synchronize the body's clock8 were handled through the same pathways that we use to see.

But recent discoveries show that the human eye has two separate light-sensing systems. One system allows us to see. The second system tells our body whether it's day or night.

36. "Poorer children" and "hungry people" are mentioned in Paragraph 2 to show

A. humans' senses are influenced by what's going on in their heads.

B. they have sharper senses than others.

C. they lose their senses because of poverty and hunger.

D. humans' senses are affected by what they see with their eyes.

37. There was a delay in Radel's experiment because

A. he needed more students to join.

B. he didn't prepare enough food for the 42 students.

C. he wanted two groups of participants, hungry and non-hungry.

D. he didn't want to have the experiment at noon.

38. Why did the 80 words flash so fast and at so small a size on the screen?

A. To ensure the participant was unable to perceive anything.

B. To guarantee each word came out at the same speed and size.

C. To shorten the time of the experiment.

D. To make sure the participant had no time to think consciously.

39. Radel's experiment discovered that hungry people

A. were more sensitive to food-related words than stomach-full people.

B. were better at identifying neutral words.

C. were always thinking of food-related words.

D. saw every word more clearly than stomach-full people.

40. It can be learnt from what Radel says that

A. humans' thinking processes are independent of their senses.

B. an experiment with hungry and non-hungry participants is not reliable.

C. humans can perceive what they need without deep thinking processes.

D. 42 participants are too small a number for a serious investigation.

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