DHAKA: Facebook secretly manipulated the feelings of 700,000 users to understand ‘emotional contagion’ in a study that prompted anger and forced the social network giant on the defensive.

For one week in 2012 – and without the explicit consent or knowledge of users – Facebook tampered with the algorithm used to place posts into their news feeds to study how this affected their mood.

The researchers wanted to see if the number of positive, or negative, words in messages they read affected whether users then posted positive or negative content in their status updates.

The study, conducted by researchers affiliated with Facebook, Cornell University, and the University of California at San Francisco, appeared in the June 17 edition of the Proceedings of the National Academy of Sciences, reports The Straits Times.

BDST: 1402 HRS, JUNE 30, 2014