In fact, the subjects had no idea that they were part of an experiment involving artificial manipulation of their news feed for the purposes of potential inducing happiness or sadness as part of a research study. This potential use of their Facebook account is simply not mentioned in the Data Use Policy. The policy states that the information provided by users may be used for research purposes. It also states that the information may be shared with outside vendors to conduct research. However, nowhere does the policy state that users agree to intentional manipulation by Facebook staff for research purposes.

The complete quote from this article:

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