It's little surprise that this idea has proven captivating because it seems so true in wildly different contexts. The average size of modern hunter-gatherer communities, it's been calculated, is 148. The average size of army companies through history, from the Romans to the USSR, hovers around And the average number of people to whom Britons send Christmas cards, according to a 2003 study, is 153. No wonder so many panic-merchants worry that online social networks will destroy society. To accumulate 1,000 online social network friends, Dunbar's Number suggests, is to violate a law as old as humanity itself. The good news is that, judging by research, the panic merchants are wrong: social networks don't replace offline friendships, turning users into people unable to converse face-to-face. Nonetheless, Dunbar's work does suggest something troubling about modern friendship. For centuries – and especially since the Industrial Revolution – we've been uprooting ourselves from the communities in which we were born. Until recently, on arriving in a new place, you'd inevitably lose your ties with the one you'd left; you'd be forced to invest fully in a new social circle. These days, however, thanks to motorways and airliners, e-mail and online social apps, you need never cut those ties. You never leave your old life behind, so your emotional investments are scattered. One consequence is that the people in your circle of 150 are far less likely to know each other. Or, as Dunbar writes, "Our social networks are no longer as densely interconnected as they once were." Anyone who's ever fled small-town life might feel relieved in some way. After all, "dense interconnectedness" in small villages could mean that there are always people who are snooping (窥探)on your business. Yet it turns out that when close friends know each other, good things happen. For example, Dunbar's research shows that people are more altruistic (利他主义的)towards each other in dense social networks. Why are densely-linked friends better friends? The reason may be that in a dense network an act of friendship is two things at once: an expression of an individual bond, and another stitch in a bigger social fabric. Now you've got a good reason to introduce your friends to each other. True, they'll probably gossip about you at some point, but then that strengthens the social fabric, too. 1)According to the passage, Dunbar's Number is__________.

Few ideas from social science have dug their way into the public imagination like Dunbar's Number, the famous finding that we humans can't cope with a social circle much larger than 150 people. It's little surprise that this idea has proven captivating because it seems so true in wildly different contexts. The average size of modern hunter-gatherer communities, it's been calculated, is 148.

The average size of army companies through history, from the Romans to the USSR, hovers around

And the average number of people to whom Britons send Christmas cards, according to a 2003 study, is 153.

No wonder so many panic-merchants worry that online social networks will destroy society. To accumulate 1,000 online social network friends, Dunbar's Number suggests, is to violate a law as old as humanity itself.

The good news is that, judging by research, the panic merchants are wrong: social networks don't replace offline friendships, turning users into people unable to converse face-to-face. Nonetheless, Dunbar's work does suggest something troubling about modern friendship. For centuries – and especially since the Industrial Revolution – we've been uprooting ourselves from the communities in which we were born. Until recently, on arriving in a new place, you'd inevitably lose your ties with the one you'd left; you'd be forced to invest fully in a new social circle. These days, however, thanks to motorways and airliners, e-mail and online social apps, you need never cut those ties. You never leave your old life behind, so your emotional investments are scattered.

One consequence is that the people in your circle of 150 are far less likely to know each other. Or, as Dunbar writes, "Our social networks are no longer as densely interconnected as they once were." Anyone who's ever fled small-town life might feel relieved in some way. After all, "dense interconnectedness" in small villages could mean that there are always people who are snooping (窥探)on your business.

Yet it turns out that when close friends know each other, good things happen. For example, Dunbar's research shows that people are more altruistic (利他主义的)towards each other in dense social networks. Why are densely-linked friends better friends? The reason may be that in a dense network an act of friendship is two things at once: an expression of an individual bond, and another stitch in a bigger social fabric.

Now you've got a good reason to introduce your friends to each other. True, they'll probably gossip about you at some point, but then that strengthens the social fabric, too.

1)According to the passage, Dunbar's Number is__________.

• A. a method to calculate the average size of modern human communities
• B. a public opinion on the potential influence of online social networks
• C. a theory that states the limit of the size of one's social circle
• D. a scientific concept that once influenced human society in history
  
  2)The word "panic-merchants" (Para. 1)refers to people__________.
• A. who have an intense fear of meeting others through online social networks
• B. who capitalize on people's worry about the impact of big online social networks on society
• C. who are afraid of the lack of privacy on social networking websites
• D. who disbelieve the power of densely connected social networks
  
  3)What is the trouble with modern friendship according to the passage?
• A. People tend to have more scattered social networks than before.
• B. People have denser social networks thanks to online social apps.
• C. People feel it easier to lose their ties with those they had left behind.
• D. People find it hard to make real friends through online social networking.
  
  4)According to the author, one bad thing about a dense social network is that__________.
• A. one's business is hard to develop
• B. one's privacy can be easily invaded
• C. one has few chances to meet new friends
• D. one has to cut ties with friends in distant places
  
  5)What is the author's overall attitude toward dense social networks?
• A. Indifferent.
• B. Unclear.
• C. Negative.
• D. Positive.