In next week's reading assignment, you will come across the term "circadian rhythm." In the news today is a study that analyzed Tweets from across the world. The researchers found that emotional tone (or mood) followed similar patterns across the day, weeks, and seasons -- in other words circadian rhythms apply to mood. This finding regarding circadian rhythms and moods is not novel, but the method of data collection and the wide range of nationalities, large sample size, etc. make this study stand out. However, as with all studies, there are limitations; for example, only Tweets in English were included and the text analysis program is not sophisticated enough to distinguish the context in which the words are used (e.g., swear words might not always mean a person is angry). As I read this article, I found myself disturbed by the method of data collection. While analyzing social media content could provide valuable research insights and large sample sizes, is doing so a violation of privacy of those who post? Or is it acceptable that if you feel comfortable enough Tweeting or posting on Facebook for the general public to view, you have given up your right to privacy? I'm not a Twitter user, but for those of you are, did you have to agree to have your Tweets used for research purposes when you signed up for an account? Or is there some way to "opt out" of having your data used in this way, similar to being able to decide not to participate in a research study during any time?