Happiness follows a U-shaped curve during a person's lifetime, according to research showing that middle-aged people are the unhappiest.

Satisfaction with life starts to drop as early as a person's late 20s and does not begin to recover until well past 50, says Bert van Landeghem, an economist at Maastricht University in Belgium. While young adults are carefree and full of hope for the future and the over-50s have come to terms with the trials of life, the research indicates that those in the middle feel weighed down by the demands on them.

The study found "a substantial dip in happiness during the middle of people's lives is the equivalent to becoming unemployed or losing a family member".

The conclusions come in a study of how people perceive their wellbeing. Mr. van Landeghem, who is 29, will present his research at the Royal Economic Society annual conference at Royal Holloway, the University of London, this week.

While Mr. van Landeghem said happiness did return with age, he warned that older people did not actually recapture the spirit of their youth. They simply learnt to be satisfied with their lot. "A U-shaped happiness curve does not necessarily imply that a 65-year-old prefers his own life to the life of a 25-year-old," he said. "Both the 25-year-old and 65-year-old might agree that it is nicer to be 25 than to be 65. But the 65 year-old might nevertheless be more satisfied, as he has learned to be satisfied with what he has.

Studies around the world have shown that happiness tends to dip in midlife, he said, and that this was not just a phenomenon confined to the Western world.

Last month, Lewis Wolpert, emeritus professor of biology at University College London, said happiness could peak as late as 80. In a book called You're Looking Very Well, Prof Wolpert said most people were "averagely happy" in their teens and 20s, but this declined until early middle age as they attempted to support a family and career.
He added: "From the mid-40s, people tend to become ever more cheerful and optimistic, perhaps reaching a maximum in their late 70s or 80s." An easing of the responsibilities of middle age, maturity and an increased focus on the things we enjoy contributed to the trend, he said.

47. According to Bert van Landeghem's research, if we draw a curve of happiness during one's lifetime, it would be .
48. Compared with both the young and the old, the middle-aged are unhappier because there are heavy demands which .
49. The decline of happiness in middle age is similar to that when people lose a job or .
50. Mr. van Landeghem suggested that happiness returns with age simply because old people learnt to face their fate with .
51. According to Lewis Wolpert, people in their late 70s or 80s may be the most .

47.答案：U-shaped。根据题干中的a curve of happiness，lifetime将本题出处定位到首段。该段介绍了Bert van Landeghem的研究发现：人一生中的快乐感是一个U-shaped curve（U曲线）。由此可知，如果我们画一条有关人一生中快乐感的曲线时，这个曲线将会是U-shaped，故答案为U-shaped。

48.答案：weigh them down。根据题干中的the middle-aged和demands将本题出处定位到第二段末句。该句提到，青年人无忧无虑，并且对未来充满希望，过了五十岁的人已经开始适应生活的种种考验，而中年人则被众多烦恼困扰。由此可知，与年轻人和老年人相比，中年人之所以更加不快乐是因为feel weighed down by the demands on them，即有很多使他们沮丧的demands。因为“沮丧”与其逻辑主语demands之间为主动关系，故用原形weigh down即可，而weigh down的宾语是the middle-aged，为避免重复，用them代替即可，故答案为weigh them down。

49.答案：a family member。空前的or表明，本空应填一与a job并列的名词（短语）。根据题干中的similar to和lose a job将本题出处定位到第三段。题干中的The decline of happiness与a substantial dip in happiness对应，in middle age与during the middle of people’s lives对应，is similar to与is the equivalent to对应，lose a job与becoming unemployed对应，or为原文信息复现，故or后的a family member即为本题答案。

50.答案：satisfaction。空前的with表明，本空应填一名词（短语）。根据题干中的returns with age和simply将本题出处定位到第五段前两句。题干中的Mr. van Landeghem…with age与Mr. van Landeghem…with age对应，simply 为原文信息复现，old people learnt to与They simply learnt to对应，故be satisfied with their lot应该与face their fate with…对应。既然是知足常乐，那也就是说对他们能以满意的心态来看待命运，故将satisfied转化为名词satisfaction即可。

51.答案：cheerful and optimistic。空前的most 表明，本空应填一形容词（短语）。根据题干中的their late 70s or 80s将本题出处定位到末段首句。题干中的According to Lewis Wolpert与该句提到的He added对应， in their late 70s or 80s为原文信息重现，may be the most与perhaps reaching a maximum对应。perhaps reaching a maximum说的是人们在late 70s or 80s时的cheerful and optimistic，即人们在快80岁或者80时时最cheerful and optimistic。