In the study, Facebook caused the news feeds of nearly 700,000 unwitting Facebook users to show an abnormally lower number of either positive or negative posts.
The study proved that the posts people saw could manipulate their emotions and determine how positive or negative they felt.
Currently, Facebook’s Data Use Policy, which all users agree to when they sign up, includes that people’s information can be used by Facebook for “internal operations,” like research and service improvement. However, Hill found that Facebook didn’t change its Data Use Policy to include those use cases until four months after it conducted the November 2012 experiment.
When it conducted its experiment, Facebook didn’t ask users for their explicit permission to include them in the study. And it didn’t implicitly ask their permission when they signed up, either.
But Facebook denies that it conducted any research without users’ permission.