Facebook waits for users to be in a good mood and then shows ads to them.

The Belgian police warned citizens to beware of using the “Reactions” button on Facebook, which they added to the site in February. With this button, users express their attitude to the publication, choosing one of six reactions - sadness, anger, love, admiration, etc.

Police found that Facebook takes into account the user's emotions to improve the effectiveness of advertising. Algorithms determine when a person is most likely in a good mood - and then they show him an advertisement.

By limiting the number of reactions to six, Facebook simplifies the work of the advertising system, because it is not so easy to process emotions from a billion users in real time.
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Customer Mood is another parameter by which advertisers can target advertising. So, a thousand impressions for happy users, obviously, will be more expensive than a thousand impressions for users in a neutral mood.

Experts warned immediately after the appearance of this feature that Facebook would use it for commercial gain. At the same time, Facebook itself insisted that reactions were made for the convenience of people, so that they could express a variety of emotions, and not just put "likes".

By the way, shortly after the launch, Facebook confirmed that anger reaction to some message is regarded as “emotional involvement”, which could lead to an increase in the number of such messages in the feed.