次の英文を読み、下記の設問に答えなさい。

Feb.14 is Valentine's Day, an annual occasion which celebrates romantic love. However, love is not only a matter of the heart. Brain researchers have discovered romance has a complex biological and chemical nature.

While our thoughts and emotions seem like invisible things without shape or form, these internal states can be analyzed by monitoring blood flow in different parts of our brain using advanced imaging techniques.

Neuroscientist Lucy Brown conducted an experiment with 17 college students, who described themselves as being in the suffering state of new love. They were subjected to brain scans and asked to look at a picture of their beloved. Without exception, the picture stimulated heightened electrical activity in two key areas of the brain.

Brown, a professor at Albert Einstein College of Medicine, says these two regions comprise the brain's reward system. A primitive part of the organ also found in other mammals, it is more closely associated with the desire for food and water than with the sex drive. “And this is the system that was active, to our amazement, in the people who were in love, ”she says. Brown notes that this is the region of the brain that lights up during a cocaine^注1 high, and is responsible for the desire that drives cocaine addiction.

A similar mix of happiness and longing is familiar to anyone who has ever been in love, which may help explain why romantic love is often a bitter-sweet experience. “It's not just happiness,” Brown says. “You can be anxious. You can actually get angry a little. But the key, the core that remains, is this motivation toward the other pet-son. That other person is a goal because they produce so much reward.”

When the brain's reward system is aroused, it releases a special chemical called dopamine^注2 Helen Fisher, a professor who worked with Lucy Brown on the brain imaging and love studies, says dopamine then spreads to other parts of the brain, each of which has its own function.

“As you reach for a piece of chocolate and want it, just as you want to do well in school, this brain system is being activated,” Fisher says. “But it is being activated with a different combination of other parts of the brain, making the experience of wanting the chocolate different than the experience of wanting a beloved.”

According to Fisher, when a pet-son first falls in love, it usually follows a distinct pattern. Everything about their beloved takes on special meaning.

“The car that they drive is different than every other car in the parking lot, the street they live on, what they wear, the music they like, the books they read. Everything about them is special - which by the way is an indication of the dopamine system in the brain.”

Fisher explains that the dopamine rush often leads to an intense focus on the be1oved. That, in turn, can lead to the emotional roller coaster ride that is a common feature of romantic love. “There is intense feeling of 'being high' when things are going well, mood swings into horrible despair when things are going poorly. And tremendous energy. You can walk all night and talk until dawn. There are all kind of physiological responses-butterflies in the stomach, a dry mouth when you talk to the person on the phone, intense desire of possession,” she says. “In other words, the full collection of personality features that are linked with romantic love are special to that particular feeling, and the reward system is part of that experience.”

Fisher offers a straightforward evolutionary explanation as to why the drive to find sex, romance and long-term partnership can be so much more persistent and intense than most other human desires.

“Charles Darwin said, ‘If you have four children and I have no children, you live on and I die out.’ So it's not how much money you make. It's not how good looking you are. It's not even how smart you are. It's how many children you have. How much of your own DNA you pass on to tomorrow,” Fisher says. “So parts of the brain are simply built to go out and find a lot of different partners, focus on just one at a time, fall in love with that individual, attach, then remain attached at least long enough to raise a child through infancy together as a team.”

This deeply rooted link between love and survival explains our cultural devotion to mating, for better or worse: “People live for love; they sing for love; they dance for love; they compose all kinds of myths and legends for love. But they also kill for love and they die for love. So love is a tremendously powerful brain system. In fact, I'd call it an addiction - a perfectly wonderful addiction when it's going well and a perfectly horrible addiction when it's going poorly.”

And like any addiction, love can cloud our judgment, leading us to peculiar behaviors, which to other people who are not in love, seem to be funny or sometimes threatening or horrifying.

• 注1:コカイン（麻薬の一種）
• 注2:ドーパミン

問 英文の内容に合うように、(1)～(5)の各文の空所を補うものとして最も適したものをそれぞれ選択肢1～4の中から選びなさい。また(6)～(10)は質問に対する答えとして最も適したものをそれぞれ選択肢1～4の中から選びなさい。

• (1) Our emotion and thinking activities have some           basis.
  • 1. musical
  • 2.biological
  • 3. visual
  • 4. economical
• (2) Students who joined the experiment conducted by Lucy Brown were those who were           a new love.
  • 1. experiencing
  • 2. rejecting
  • 3. seeking
  • 4. disguising
• (3) None of the pictures shown in the experiment           to provoke the enhanced electrical activity in some areas of the brain.
  • 1. failed
  • 2. caused
  • 3. appeared
  • 4. followed
• (4) When dopamine is produced, it is conveyed to different parts of the brain depending on the          .
  • 1. emotion
  • 2. focus
  • 3. function
  • 4. person
• (5) According to the article, when someone first falls in love, they tend to recognize everything linked to the beloved with special meaning, which otherwise would be just           things.
  • 1. ordinary
  • 2. useful
  • 3.unnecessary
  • 4. peculiar
• (6) Why is our drive to find sex, romance and long-term partnership so persistent and intense?
  • 1. Because we tend to choose money rather than having children.
  • 2. It is because we want our children to inherit our DNA.
  • 3. This drive comes from our fear of how much DNA we can retain tomorrow.
  • 4. It is because we are so keenly attached to raising children.
• (7) What is the “emotional roller coaster ride” during the period of romantic love?
  • 1. It is the pleasant and happy experience of a new love.
  • 2. It is the feeling that everything that is linked with the beloved is special.
  • 3. It is the negative situation where you become suddenly anxious or angry without understanding the reasons.
  • 4. It is the situation where the extreme sense of fulfillment suddenly turns into a complete depression when something works negatively.
• (8) Why does a person in love sometimes walk all night or talk until dawn?
  • 1. They do such things because these behaviors are in part triggered by our reward system.
  • 2. Because the special feelings of romantic love very often lose our energy.
  • 3. Because such a person has a special mix of happiness and longing caused by a roller coaster.
  • 4. They behave this way in order for their DNA to survive, even long after their death.
• (9) Why can love sometimes be dangerous or fearful?
  • 1. Because it often leads us to strange and peculiar heart problems.
  • 2. Because love may destroy our calm inner discipline, leading us to kill others or ourselves.
  • 3. Because people in love will do anything to destroy the things linked with the beloved.
  • 4. Because those who seldom fall in love have threatening or horrifying features.
• (10) What is the best title for this story?
  • 1. The Never-Ending Nature of Love
  • 2. Love Makes Us Strange Creatures
  • 3. Love is a Matter of the Brain
  • 4. Invisible Love and Invisible Behavior