Abstract: A method comprising: during a first time period, obtaining one or more first content ratings of a particular content item from one or more first users, each first content rating defining a first user measure of a belief state of the particular content item; and generating a first content score for the particular content item, the first content score defining a crowd-sourced measure of the belief state of the particular content item; during a second time period, obtaining one or more second content ratings from one or more second users for the particular content item, each second content rating defining a second user measure of the belief state of the particular content item; and generating a second content score for the particular content item, the second content score defining a second crowd-sourced measure of the belief state of the particular content item; comparing the second crowd-sourced measure of the belief state of the particular content item against each of the one or more first content ratings of t