The perception of pain is so fundamental to our survival that it affects our brains in profound ways. There is not one single pain center ; instead, the whole brain lights up like a Christmas tree when pain is perceived. In the short term we are immediately prompted to protect the painful area, to remove it from the source of the pain and often to cease all use of the affected area while we examine (1)it. In the longer term, our subconscious behavior is altered. If we hit our head on a specific low beam or handle, next time we'll (2)duck. An experience of pain that lasts for long, continuous periods may affect our emotions and attitudes. We may develop depression and become less active. Alternatively, a severe experience of pain and a conscious awareness of exactly what led to that pain may result in the development of an aversion to anything resembling the cause. ( A ) We call that aversion fear. The aversion may become a long-term subconscious memory that lasts far longer than your memory of the event that caused (3)it. You may no longer remember the time you fell off the high wall and painfully twisted your ankle as a child, but your fear of heights may still be with you. ( B )

We don't always perceive pain. Even when the nerve cells are sending us pain signals, there are times when it is more important for us simply to run away, rather than roll about on the ground in agony. So there are regions of the brain that actively [ X ] our perception of pain, sometimes for just a few minutes, sometimes for several days. But there are also areas of the brain that do the reverse, and make us hypersensitive to pain. ( C )

Astonishingly, there used to be considerable confusion about when we first start experiencing pain. A hundred years ago it was widely accepted that newborn babies simply did not perceive pain at all, because their brains had not developed sufficiently.(4)Perhaps rather cruelly by today's standards, for decades many 'pin-prick' experiments were conducted on sleeping infants in attempts to understand the onset of pain perception. Much confusion was caused in those early experiments by the seeming lack of sensitivity of babies straight after birth, which turned out to be because the mothers had received anesthetics while giving birth, and (5)the babies received a small dose via their umbilical cords. Today (as anyone with children can affirm), it is well understood that a baby in pain will show clear discomfort. ( D ) Crying, (6)wriggling, fisting, large muscle movements, accompanied by clear respiratory and hormonal changes and (7)erratic sleep, are all clear signs of pain. But those early scientifically (8)flawed experiments sadly resulted in a culture that disregarded the pain of babies for much too long , despite the true scientific findings.

[Adapted from Peter J. Bentley, The Undercover Scientist, 2009. ]

• 問1. 下線部(1), (3)のitが示す内容を、それぞれ本文中の英語で答えなさい。
• 問2. 下線部(2), (6), (7), (8)の語の本文中での意味と最も近い意味を表す語を、それぞれ1～4の中から1つずつ選び、番号で答えなさい。
  • (2) duck
    • 1. dunk
    • 2. falter
    • 3. halt
    • 4. stoop
  • (6) wriggling
    • 1. wavering
    • 2. writhing
    • 3. wreathing
    • 4. wrinkling
  • (7) erratic
    • 1. irrelevant
    • 2. irregular
    • 3. infantile
    • 4. intrinsic
  • (8) flawed
    • 1. clumsy
    • 2. faulty
    • 3. naïve
    • 4. pristine
• 問3. 次の文を本文中の( A ), ( B ), ( C ), ( D )のいずれかに挿入する場合、どこが最も適切な箇所か。 1つ選び、記号で答えなさい。

  When we're safe and recovering, such heightened sensations might, for example, encourage us to avoid using the painful part while it heals.

• 問4. 前後関係から考えて、 [ X ]に入れるのに最も適切なものを1～4の中から1つ選び、番号で答えなさい。
  • 1. induce
  • 2. inform
  • 3. inhibit
  • 4. immerse
• 問5. 下線部(5)において、赤ん坊は、わずかな量(a small dose)の何を受け取ったのか。 前後関係から考えて、日本語で答えなさい。
• 問6. 本文の中で述べられている内容と一致する内容を表している文を1～5の中から1つ選び、記号で答えなさい。
  • 1. When pain is perceived, a specific pain center in our brain lights up.
  • 2. Long-lasting pain keeps us from developing depression and becoming less active.
  • 3. A fear of heights is usually caused by the experience of breaking a leg.
  • 4. Some regions in our brain make us extremely sensitive to pain.
  • 5. A newborn baby's brain has not developed enough to perceive pain.
• 問7. 下線部(4)を和訳しなさい。