The word It in “It can be strengthened” (paragraph 3) refers...

    "Checking Facebook should only take a minute." Those are the famous last words of countless people every day, right before getting sucked into several hours of watching cat videos or commenting on Instagrammed sushi lunches. That behavior is natural, given how the Internet is structured, experts say. The Internet’s omnipresence and lack of limits encourage people to lose track of time, making it hard to exercise the self-control to turn it off.

    "The Internet is not addictive in the same way as pharmacological substances are," said Tom Stafford, a cognitive scientist at the University of Sheffield in the U.K. "But it's compulsive; it's compelling; it's distracting." Humans are social creatures. Therefore, people enjoy the social information available via email and the Web.     

    The main reason the Internet is so addictive is that it lacks boundaries between tasks, Stafford said. Someone may set out to "research something, and then accidentally go to Wikipedia, and then wind up trying to find out what ever happened to Depeche Mode," Stafford said, referring to the music band. Studies suggest willpower is like a muscle: It can be strengthened, but can also become exhausted. Because the Internet is always "on," staying on task requires constantly flexing that willpower muscle, which can exhaust a person's self-control.

    For those who want to loosen the grip of the Web on their lives, a few simple techniques may do the trick. Web-blocking tools that limit surfing time can help people regain control over their time. Another method is to plan ahead, committing to work for 20 minutes, or until a certain task is complete, and then allowing five minutes of Web surfing, Stafford said.

(Adapted from: http://www.mnn.com/green-tech/computers/stories/why-the-internet-is-so-addictive)