The following text is for questions 21 to 23.

    Using social media too much and posting many selfies have caused a rise in narcissism, according to a new study. Narcissism is when people become very selfish and believe they are very talented and beautiful. They need attention from other people and think they are better than everyone else. Researchers at universities in Swansea and Milan found that heavy users of social media sites showed a 25 per cent rise in narcissism in just four months. The researchers studied how 74 people aged 18 to 34 used social media and looked at how their personality changed. They said that posting selfies seemed to increase levels of narcissism in a way that text messaging does not.

    Professor Phil Reed, from the Department of Psychology at Swansea University, said "There have been suggestions of links between narcissism and the use of selfies on social media, but until this study, it was not known the growth in narcissism. The results of this study suggest that posting selfies can increase narcissism." Professor Reed said that about 20 per cent of people may be at risk of developing narcissism. This is because they need attention and likes from other people after they post a selfie. They also want to show others how their lives are better or how they are more beautiful or attractive.

(Adopted from: https://breakingnewsenglish.com/1811/181113-social-media.html (April 25, 2019))

" ... it was not known the growth in narcissism." (Paragraph 2)

Which sentence has the word which meaning is similar to the underlined word above?