However, the "screen time" hypothesis, advanced by researchers such as Jean Twenge, is that electronic devices and excessive time spent online may have reversed these trends in recent years, causing problems for young people's psychological health.

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In fact, when Twenge previously used this data to suggest a screen time effect, some commentators were quick to raise this problem.

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In response to past critics, Twenge and her co-researchers stress they are not trying to prove that the use of digital devices reduces young people's well-being.

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There is another explanation that Twenge and her colleagues wanted to address: the impact of the great recession of 2007-2009, which hit a great number of American families and might be affecting adolescents.

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This time around, Twenge and her team make a point of saying that they are not trying to establish causes as such, but that they are assessing the plausibility of potential causes.

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To investigate, Twenge and her colleagues dived into the "Monitoring the Future" dataset based on annual surveys of American school students from grades 8, 10, and 12 that started in 1991.

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Twenge and her colleagues also found that across the key years of 2013-16, well-being was indeed lowest in years where adolescents spent more time online, on social media, and reading news online, and when more youth in the United States had smartphones.

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Twenge and her colleagues wanted to understand why this change in average well-being occurred.

2019年12月六级真题（第一套）阅读 Section B