The author responsible for the latest Facebook psychology experiment has apologized for any anxiety that may have been inflicted on unwitting participants, and for the way in which the research paper described the controversial experiment.

Conducted jointly by researchers from the University of California and Cornell University, the week-long Facebook study sought to find evidence of an “emotional contagion” that could be spread through social networking sites. In order to achieve this, a team of social scientists manipulated the News Feed items of over 689,000 Facebook users, dividing the subjects into two subsets – those who were provided News Feed items that were mostly positive, and those who were provided News Feed items that were mostly negative.

The study, entitled Experimental Evidence of massive-scale emotional contagion through social networks, provided data that suggested a so-called emotional contagion could be transferred through social networks, without the need for face-to-face interaction or non-verbal cues. Individuals exposed to predominately negative News Feed items were subsequently found to upload more posts of a negative nature. As expected, people who received positive News Feed items were more likely to upload positive posts.

All in all, more than three million Facebook posts were analyzed during the investigation.

The experiment sparked considerable outcry from users of the social network platform, many of whom were disillusioned that the research team failed to obtain the explicit consent of its participants. Facebook responded by claiming there had been “… no unnecessary collection of people’s data.” On previous occasion, the research team had also argued they were operating within Facebook’s data guidelines.

Adam Kramer, one of the project’s three research authors, recently took to Facebook to offer his apologies and address some of the criticism waded against the study:

“My co-authors and I are very sorry for the way the paper described the research and any anxiety it caused. In hindsight, the research benefits of the paper may not have justified all of this anxiety.”

However, in defending his team’s efforts, Kramer said he felt it was “… important to investigate the common worry that seeing friends post positive content leads to people feeling negative or left out.” Kramer also stated that he cared about the service’s emotional impact on its users. He was also keen to point out that the study did not seek to hide any Facebook user’s posts, saying they remained visible in friends’ timelines.

Kramer accepted the team had not clearly stated the motivations behind the study, before explaining that Facebook would learn from the reaction to the paper:

“While we’ve always considered what research we do carefully, we (not just me, several other researchers at Facebook) have been working on improving our internal review practices. The experiment in question was run in early 2012, and we have come a long way since then. Those review practices will also incorporate what we’ve learned from the reaction to this paper.”